Symposium Organizers
Santanu Bag, Air Force Research Laboratory
Edward (Ted) Sargent, University of Toronto
Patrick J Smith, The University of Sheffield
Teodor Todorov, IBM T.J. Watson Research Center
Symposium Support
MilliporeSigma (Sigma-Aldrich Materials Science)
NovaCentrix
Strem Chemicals, Inc.
EM10.01: Colloidal Nanocrystal Building Blocks I
Session Chairs
Santanu Bag
Edward (Ted) Sargent
Susanna Thon
Monday PM, November 27, 2017
Hynes, Level 1, Room 103
8:00 AM - *EM10.01.01
Exploiting the Nanocrystal Library to Construct Electronic and Optical Devices
Cherie Kagan 1
1 , University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractSynthetic methods produce libraries of colloidal semiconducting, metallic, and insulating nanocrystals tailorable in their size, shape, and composition. In this talk, we exploit the diversity in colloidal nanocrystals to construct mesoscale materials for semiconductor electronics and optoelectronics and plasmonic optical metamaterials. Chemical exchange of the long ligands used in nanocrystal synthesis with more compact ligand chemistries brings neighboring nanocrystals into proximity and increases interparticle coupling. In semiconductor nanocrystal solids, we show strong electronic coupling in combination with doping allows us to control the carrier type and concentration and design high mobility n- and p-type materials. We give examples where n- and p-type semiconductor nanocrystal solids are used to construct field-effect transistors and integrated circuits and solar photovoltaics.1–3 In metal nanocrystal solids, ligand-controlled coupling allows us to tailor a dielectric-to-metal phase transition seen by a 1010 range in DC conductivity and a dielectric permittivity ranging from everywhere positive to everywhere negative across the whole range of optical frequencies.4 We realize a "diluted metal" with optical properties not found in the bulk metal analog, presenting a new axis in plasmonic materials design and the realization of optical properties akin to next-generation metamaterials. We harness the properties of metal NCs by using nanoimprint lithography to print large-area metamaterials on glass and plastics with widely tailorable optical properties that are used to realize near-infrared optical devices.5 Exploiting the nanocrystal library, we use metal, semiconductor, and insulating nanocrystals to create high conductivity electrodes, high mobility channel layers, and high dielectric constant gate insulator layers and ultimately solution-processable, all-nanocrystal field-effect transistors fabricated on flexible plastics with electron mobilities of 21.7 cm2/Vs.6
(1) Choi, J.-H.; Fafarman, A. T.; Oh, S. J.; Ko, D.-K.; Kim, D. K.; Diroll, B. T.; Muramoto, S.; Gillen, G.; Murray, C. B.; Kagan, C. R. Nano Lett. 2012, 2631–2638.
(2) Oh, S. J.; Berry, N. E.; Choi, J.-H.; Gaulding, E. A.; Paik, T.; Hong, S.-H.; Murray, C. B.; Kagan, C. R. ACS Nano 2013, 7 (3), 2413–2421.
(3) Stinner, F. S.; Lai, Y.; Straus, D. B.; Diroll, B. T.; Kim, D. K.; Murray, C. B.; Kagan, C. R. Nano Lett. 2015, 15 (10), 7155–7160.
(4) Fafarman, A. T.; Hong, S.-H.; Caglayan, H.; Ye, X.; Diroll, B. T.; Paik, T.; Engheta, N.; Murray, C. B.; Kagan, C. R. Nano Lett. 2013, 13 (2), 350–357.
(5) Chen, W.; Tymchenko, M.; Gopalan, P.; Ye, X.; Wu, Y.; Zhang, M.; Murray, C. B.; Alu, A.; Kagan, C. R. Nano Lett. 2015, 15 (8), 5254–5260.
(6) Choi, J.-H.; Wang, H.; Oh, S. J.; Paik, T.; Sung, P.; Sung, J.; Ye, X.; Zhao, T.; Diroll, B. T.; Murray, C. B.; et al. Science (80-. ). 2016, 352 (6282), 205–208.
8:30 AM - EM10.01.02
A Reflective Front Contact Improves Infrared Light Absorption in Colloidal Quantum Dot Solar Cells
Olivier Ouellette 1 , Nadir Hossain 1 , Brandon Sutherland 1 , Amirreza Kiani 1 , F. Pelayo Garcia de Arquer 1 , Hairen Tan 1 , Mohamed Chaker 2 , Sjoerd Hoogland 1 , Edward (Ted) Sargent 1
1 , University of Toronto, Toronto, Ontario, Canada, 2 , INRS, Varennes, Quebec, Canada
Show AbstractPbS colloidal quantum dots (CQDs) hold great promise for solution-processed photovoltaic applications. Their tunable bandgap allows PbS CQDs to harvest sunlight in the infrared range, beyond silicon's 1100nm bandgap. In that spectral range, however, the active layer thickness required to absorb infrared light greatly exceeds the charge carrier diffusion length, thus severely limiting power conversion efficiency. We solved this problem by engineering the reflectivity of the front contact of a PbS CQD solar cell in order to take advantage of constructive optical interference in the active layer. This resonant cavity-enhanced strategy allowed us to increase light absorption beyond 1100 nm by 56% and reach an external quantum efficiency of 60% at 1300 nm with a thin, 95nm-thick CQD layer. These results, along with the simple analytical model presented, provide a basis to rationally exploit light interference in thin film solar cells, especially those intended for tandem application.
8:45 AM - EM10.01.03
Carrier Dynamics and Diffusion Lengths in Mixed-Quantum-Dot Solar Cells
Andrew Proppe 1 , Zhenyu Yang 1 , James Fan 1 , Oleksandr Voznyy 1 , Edward (Ted) Sargent 1
1 , University of Toronto, Toronto, Ontario, Canada
Show AbstractColloidal quantum dots (CQDs) are solution processable optoelectronic materials that can be used to fabricate inexpensive photovoltaics and LEDs. One major performance limitation of solar cells based on PbS CQDs is the diffusion length of photogenerated carriers, which should be at least the length of the active layer for efficient charge collection. Bulk heterojunction (BHJ) device architectures can be used as a strategy to overcome low diffusion lengths, but has not yet been demonstrated for PbS-only CQD solar cells. In this work, we use two solution-phase ligand exchanges, where two types of QDs are exchanged separately and the ligands raise (lower) the bands to form donor (acceptor) QDs. When these QDs are mixed together in solution as a concentrated ink, they retain their surface ligands and donor / acceptor character. This allows us to build thicker active layers, achieving higher efficiencies (10.6%) resulting from a 20% increase in current, attributed to higher diffusion lengths enabled by percolation pathways of donor / acceptor CQDs. I will discuss the chemical and photophysical characterization of this new mixed PbS CQD solid, and additionally will discuss the use of transient absorption to obtain diffusion lengths and dot-to-dot transfer rates in QD solids.
9:00 AM - EM10.01.04
Halide Re-Shelled Quantum Dot Inks for Infrared Photovoltaics
James Fan 1 , Mengxia Liu 1 , Oleksandr Voznyy 1 , Bin Sun 1 , Larissa Levina 1 , Rafael Quintero-Bermudez 1 , Min Liu 1 , Olivier Ouellette 1 , F. Pelayo Garcia de Arquer 1 , Sjoerd Hoogland 1 , Edward (Ted) Sargent 1
1 Electrical and Computer Engineering, University of Toronto, Toronto, Ontario, Canada
Show AbstractColloidal quantum dots are promising materials for tandem solar cells complementary to silicon and perovskites. These devices are fabricated from solution phase; however, existing methods for making infrared-bandgap CQD inks suffer agglomeration and fusion during solution exchange. Here we develop a new ligand exchange that provides robust surface protection and thereby avoids aggregation. First, we exchanged long oleic acid ligands to a mixed system comprised of medium-chain ammonium and anionic chloride ligands; then, we re-shelled the surface using short halides and pseudohalide ligands that enabled transfer to a polar solvent. Absorbance and photoluminescence measurements reveal the retention of the excition sharpness, while x-ray photoelectron spectroscopy presents increased halide capping.The best power conversion efficiency of these devices is 0.76 power points after filtering through silicon, which is 1.9x higher than the previous single-step solution-processed IR-CQD solar cell.
9:15 AM - EM10.01.05
High-Brightness, “Droop-Free” Quantum Dot Light Emitting Diodes
Jaehoon Lim 1 2 , Young-Shin Park 1 2 , Kaifeng Wu 2 , Hyeong Jin Yun 2 , Victor Klimov 2
1 , Center for High Technology Materials, Albuquerque, New Mexico, United States, 2 Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractRecent progress in high-emissivity colloidal QDs has led to rapid advances in QD-based light emitting diodes (QLEDs) that have reached peak external quantum efficiencies (EQEs) near the theoretical maximum (~20%, Nature, 2014). One of the remaining challenges in this field is a so-called "droop effect," that is, the reduction of the device efficiency at high driving currents which limits the achievable brightness levels. Here, we demonstrate the elimination of efficiency droop in QLEDs via thorough engineering of both the device architecture and the internal structure of the QD. A critical innovation in this work is a new class of type-I QDs with a finely graded composition. Applying delicate control of reaction kinetics, we design the QD heterostructure such as to produce a “smooth” confinement potential for both electrons and hole which allows us to greatly suppress Auger recombination. We further incorporate a specially shaped tunneling barrier to achieve balanced electron and hole injection. In addition to high single-exciton emission efficiencies, these newly developed QDs exhibit exceptionally high emission quantum yields for charged and neutral multiexciton states which is key to maintaining high emissivity at high currents. To facilitate balanced carrier injection, we utilize the inverted device architecture (Nano Lett., 2011) with the conductivity-controlled ZnO/polyvinylpyrollidone hybrid electron transport layer. The fabricated devices exhibit the peak EQE of 13.5%, which is near the limit estimated from the product of the photoluminescence efficiency of solution-based samples (~70%) and a standard outcoupling efficiency (~20%). Importantly, the high EQE values are maintained in the range of high driving currents indicating a complete suppression of the droop effect up to brightnesses of ~100,000 cd m-2. Using these devices, we are able to achieve record-high luminances of >300,000 cd m-2 which suggest their potential suitability for previously unattainable applications such as QLED projectors, daylight displays, outdoor lighting, and industrial light sources.
10:00 AM - *EM10.01.06
Color-Tuned Large Area Colloidal Quantum Dot Photovoltaics
Susanna Thon 1
1 , Johns Hopkins University, Baltimore, Maryland, United States
Show AbstractInorganic colloidal quantum dots (CQDs) are an attractive material for color-tuned and transparent solar cells because they combine flexible, low cost solution-phase synthesis and processing with tunable bandgaps via the quantum confinement effect. CQD solar cells typically consist of several optically thin active and electrode layers that are optimized for their electrical properties; however, their spectral tunability beyond the absorption onset of the CQD layer itself has been relatively unexplored. I will present results on a new optimization method for designing color-tuned and transparent CQD devices for potential use in building- and vehicle-integrated photovoltaics. We use multi-objective optimization algorithms and thin film interference engineering to quantify the tradeoffs between attainable color or transparency and available photocurrent, calculate the effects of non-ideal interference patterns on apparent device color, and apply our optimization method to tandem solar cell design. We have fabricated blue, green, yellow, red and semitransparent devices with high photocurrents. I will discuss how our optimization method provides a general platform for custom-design of optoelectronic devices with arbitrary spectral profiles. Additionally, I will introduce methods for scaling up the power output of CQD and related solution-processed solar cells to commercially viable levels without requiring large-area uniform films.
10:30 AM - EM10.01.07
Epidermal Passive Matrix Quantum Dot Light-Emitting Diodes as an Information Display for Multi-Functional Wearable Electronics
Hyung Joon Shim 1 2 , Jaemin Kim 1 2 , Jiwoong Yang 1 2 , Woongchan Lee 1 2 , Jun-Kyul Song 1 2 , Dong Chan Kim 1 2 , Seungki Hong 1 2 , Taeghwan Hyeon 1 2 , Dae-Hyeong Kim 1 2
1 , Institute for Basic Science (IBS), Seoul Korea (the Republic of), 2 , Seoul National University, Seoul Korea (the Republic of)
Show AbstractAs an information output port from the wearable electronics, demand for wearable displays has been rapidly growing. And now that the research scope of wearable electronics has expanded to the field of extremely thin epidermal electronics, an ultrathin flexible display has become a critical component in next-generation wearable electronics. In this regard, many kinds of thin and/or micro-size light-emitting diodes (LEDs), including inorganic micro-LEDs (iLEDs), polymer LEDs (PLEDs), and organic LEDs (OLEDs), have been fabricated on deformable substrates. However, practical challenges remain, such as high operating voltages, relatively thick form factors of final devices, and unsatisfactory stability and performance. Here, quantum dot (QD) LEDs can offer unique and attractive characteristics that make them particularly suitable for next-generation wearable displays, including narrow bandwidths that enable high color purity, high electroluminescence (EL) brightness at low operating voltages, high photo/air stability, high resolution patternability, and easy processability for device integration. We therefore developed ultrathin red, green, and blue (RGB) QLED displays that utilizes passive matrix to address individual pixels. The ultra-thin thickness (~5.5 μm) of the ultrathin QLED display enables its conformal contact with the wearer’s skin, thereby reducing discomfort and preventing its failure under vigorous mechanical deformations. The QDs with a relatively thick shell thickness are employed to improve Electroluminescence characteristics (e.g., brightness up to 44,719 cd m-2 at 9 V, which is the highest record among wearable LEDs reported to date) by suppressing the nonradiative recombination. Owing to this high performance, the display base on an array of QLEDs provides satisfactory brightness with a minimal temperature increase during its sequential scanning operation. Various patterns, including letters, numbers, symbols, and animations can be successfully visualized on the skin-mounted QLED display. Furthermore, the combination of the ultrathin QLED display with flexible driving circuits and wearable sensors results in a fully integrated QLED display that can directly show sensor data.
10:45 AM - EM10.01.08
Effect of Electrode on Spectrum Selectivity and Photoresponse of the Colloidal-QD Based Schottky Photodiode
Hemant Kumar 1 , Yogesh Kumar 1 , Bratindranath Mukherjee 2 , Gopal Rawat 1 , Chandan Kumar 1 , Bhola Nath Pal 3 , Satyabrata Jit 1
1 Electronics Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi India, 2 Metallurgical Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi, Uttar Pardesh, India, 3 SMST, Indian Institute of Technology (Banaras Hindu University), Varanasi India
Show AbstractIn this paper the colloidal CdSe quantum dots (QDs) and ZnO QDs based low-cost, solution processed Schottky photodiode on an ITO-coated glass substrate is reported with Au and Pd contacts. The effect of top electrode on the spectrum selectivity of the Schottky photodiode is analyzed possibly for the first time. The introduction of Pd as top electrode compared to Au increase the spectrum selectivity of the devices by reducing the FWHM from 189.6 nm to 60.82 nm. The high spectrum selectivity achieved by the optical cavity formed by Pd and wide-band gap semiconductor (ZnO) leads to the increase in absorption of CdSe QDs by reflecting the light waves (400 - 470 nm) from the interface of CdSe QDs/Pd. This optical cavity enhances the EQE of Pd-based photodiode three times from 0.87% to 2.21% compared to the Au-based photodiode at 400 nm wavelength for an applied bias of zero volts. Further, the Pd-based Schottky photodiode also shows superior time response (average of rise and fall time) of 17.15 sec compared to 28.9 sec of the Au-based Schottky photodiode for an applied pulse train of white LED light for 1 sec. The theoretical model using the Fresnel’s equations are also derived from finding the analytical reason for increment in photoresponse with the narrowing of FWHM. Furthermore, the optical study of the complete device is also analyzed for the resonant cavity effect with and without electrodes. CdSe QDs act as an optical spacer in the optical cavity between wide band-gap semiconductor ZnO QDs and metal electrodes (Au or Pd). The effect of optical spacer (CdSe QDs) thickness is analyzed on the photoluminescence, reflection, and transmittance of the complete device.
11:00 AM - EM10.01.09
Dramatically Enhanced Photosensitivity of Quantum Dot Thin-Films Enabled by Surface Functionalization and Heterojunction Semiconducting Structures
Jaehyun Kim 1 , Jingu Kang 1 , Myunggil Kim 1 , Sung Kyu Park 1
1 , Chung-Ang University, Seoul Korea (the Republic of)
Show AbstractRecently, photosensing platforms using hybrid device structures have received lots of attention due to their potentials of synergic effect of two materials and increasing application area using various materials. In particular, InGaZnO (IGZO) TFTs showed excellent electrical performance such as high field-effect-mobility, stability, and low off-current level, and quantum dots (QDs) has been widely developed as a promising photodetector materials due to their high surface-to-volume ratio and size-tunable fluorescence.
For the IGZO/QDs hybrid photosensor, the characteristics of QDs ligands are very important in the photogenerated charge transport mechanism. Long oleic acid ligands conventionally used in QDs synthesis result in very poor charge transport interactions due to their insulating properties. Therefore, various short and conducting ligands such as thiocyanate (SCN) have been widely used in order to enhance electronic transport. Here, we found that molecular metal chalcogenide surface ligands such as Sn2S64- can greatly improve performance and stability of QDs resulting in considerablly enhanced photosensitivity.
In our experiments, it was revealed that the IGZO TFTs showed inconsiderable photoresponse to visible light due to the wide energy bandgap. In addition, IGZO/CdSe QDs with oleic acid ligands showed less photoresponse than pristine IGZO TFTs, possibly due to insulating properties of long organic ligand chain. Incident light is scarcely absorbed in IGZO channel layer because CdSe QDs layer covers the IGZO and blocks the light, so not only oxygen vacancies in the deep state of IGZO channel cannot ionize, but also CdSe QDs cannot transfer the photo-generated electrons due to the long ligands. Additionally, IGZO/CdSe QDs with SCN- ligands showed larger photoresponse characteristic because of short and conducting properties of SCN- ligands. However SCN- ligands can be easily separated from CdSe QDs because of weak chemical coupling energy of single bond so that there are a lot of defect sites on the surface of CdSe QDs resulting in trapping photo-generated electrons and obstructing charge carrier. On the other hand, Sn2S64- ligands form stable conjugated double bonds, so that there are few or no defect trap sites on the surface of CdSe QDs. Consequently, photo-generated electrons from the CdSe QDs can be perfectly transferred to the conduction band of the IGZO channel layer with much less trapping problem while photo-generated holes are trapped on the CdSe QDs or interfaces of CdSe QDs/IGZO interface due to the large energy barrier between the valence band maximum of CdSe QDs and IGZO semiconductor. Therefore, IGZO/CdSe QDs with Sn2S64- ligands showed ultra-high photosensitivity and photodetectivity of 2×103 A W-1 and 4×1016 Jones, respectively. All of the phenomena were clearly observed throughout a wide array of in-situ spectroscopic analysis and electrical measurements and will be announced in the presentation.
11:15 AM - EM10.01.10
Enhanced Photocarrier Diffusion Length in Quantum Dot Solids Via Ligand-Confined Low-Dimensional Matrix
Jixian Xu 1 , Oleksandr Voznyy 1 , Mengxia Liu 1 , Ahmad Kirmani 2 , Edward (Ted) Sargent 1
1 , University of Toronto, Toronto, Ontario, Canada, 2 , King Abdullah University of Science and Technology, Saudia Arabia (KAUST), Thuwal Saudi Arabia
Show AbstractColloidal quantum dots (CQDs) are compelling optoelectronics materials because of their solution-processability and widely tunable absorption spectrum controlled by the nanocrystal size. Fundamental challenges remain for extending the photocarrier diffusion length in QD solids so that thicker solar devices can be constructed to maximize light harvesting. Previous attempts have focused on improving the ligand-exchange process. However, the influence and evolution of the microscopic nature of the matrix material produced from the ligand-exchange have been overlooked.
In this work, we report a new materials engineering strategy for the matrix of colloidal quantum dot (CQD) solids that leads to substantially improved photocarrier diffusion lengths and record-performing certified QD solar cells.
Here, we concentrate our efforts on creating ideal matrix’s microstructure that was not implemented before: reducing its dimensionality atomically between QDs and improving its global homogeneity throughout the film. We realize this by forming a PbI2-hybrid amine complex that self-limits the matrix to a monolayer configuration similar with 2D perovskites. This new chemistry process enables us to achieve unprecedented packing density and uniformity in QD PV films (characterized by synchrotron X-ray studies), and therefore significantly reduces the structural and energetic disorder that delocalizes photocarriers.
This advance translates directly into the concurrent enhancement of current density (Jsc) and the open-circuit voltage (Voc), overcoming the long-lasting compromise caused by inhomogeneous surface fusion that occurs during QD densification.
More intriguingly, the significantly extended diffusion lengths enable to build PV devices with the thickest CQD active layer solids ever reported. In 600 nm thick planar devices (the thickness of best previously-published devices is 350nm), the short current densities (Jsc) reach an unprecedented level of ~32 mA cm-2.
The certified solar-to-electricity conversion efficiencies (PCE) exceed 12% in QD devices without external optical optimization (such as anti-reflection coatings), the highest ever reported.
11:30 AM - EM10.01.11
Room Temperature Sub-kT Photoluminescence Linewidth Using Compositionally Graded Quantum Dots
Young-Shin Park 1 2 , Jaehoon Lim 2 , Victor Klimov 2
1 , University of New Mexico, Albuquerque, New Mexico, United States, 2 Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractColloidal semiconductor quantum dots (QDs) feature high photoluminescence (PL) quantum yields (QYs), size-tunable emission colors, and low-cost solution processibility. These favorable properties make them attractive materials for a range of applications including light-emitting diodes (LEDs), lasers, and luminescent solar concentrators. Nowadays, QDs can be routinely synthesized with PL QYs approaching 100% and wide color tunability ranging from near infrared to ultraviolet. One of the remaining challenges is reducing the PL linewidth at both single-dot and ensemble levels which would translate into improved color definition in the case of, for example, LEDs and display applications. A related and still unanswered question is on the ultimate PL linewidth achievable with colloidal QDs.
Here we demonstrate the possibility of realizing a sub-kT room-temperature, single-dot PL linewidth in QDs with a radially graded composition. In these structures, the CdSe core is overcoated with an intermediate layer of Cd1-xZnxSe wherein x continuously varies from 0 to 0.7, and then capped with a thin ZnSeS shell. These QDs show a remarkably narrow PL spectrum with just ~20 meV width (or 6.3 nm in terms of a wavelength) which is the smallest room-temperature line broadening ever observed for any types of colloidal nanocrystals including CdSe nanoplatelets. These dots also exhibit negligibly small spectral diffusion and wandering on time scales down to 1ms (instrumental limit of our measurements). Due to very small emission linewidth, we are able to resolve the fine structure of the PL spectrum (a PL doublet), which is not due to the effect of phonon replicas but rather directly reflects the fine structure of the band-edge exciton states. In our analysis of these remarkable spectroscopic observations we consider factors such as the effect of lattice deformation on the exciton fine structure and the influence of the shape of the confinement potential on the strength of exciton-phonon coupling, and further discuss them in the context of microstructural studies used to assess the compositional profile within the QD as well as spatial distribution of lattice strain.
11:45 AM - EM10.01.12
Designing Coupled Quantum Dot with ZnS-CdSe Hybrid Structure for Enhancing Exciton Lifetime
Raj Pala 1
1 , Indian Institute of Technology at Kanpur, Kanpur India
Show AbstractFabrication of coupled quantum dot (CQD) may provide an excellent platform for the realization of high end opto-electronic applications as well as quantum information processing. CQD can be synthesized by well-known cation exchange method and less explored ‘nanoparticle fusion’ method, in which the latter involves the coupling between constituting facets of two different semiconductors. Herein, we elucidate the mechanistic formation pathway of different heterostructures with ZnS and CdSe quantum dots (QD) with an emphasis on the formation of CQD comprised of bicompartmental Janus structure (i.e. Janus structure consisting of two compartments with the two QDs coupled) via ‘nanoparticle fusion’. With increase in the ratio of Cd/Zn from 0.9:1 to 1.3:1 to 2.5:1 to 4:1 to 12:1, we observe the evolution of structure from CdZnSeS alloy to Acorn Janus to Bicompartmental JanusA with ZnS Zinc Blende (ZB) – CdSe Wurtzite (Wz) to Bicompartmental JanusB (ZnS/CdSe-both ZB) and eventually to CdZnSeS alloy core - CdSe thick shell. Interestingly, the CQD possess two distinct emission bands (570/630 nm) in which 570 nm emission arises from the formation of new electronic states due the strong coupling between the two QDs whereas 630 nm is the characteristic CdSe emission. Further, the coupling enhances the exciton lifetimes of 570/630 nm emission (Bicompartmental JanusA - 36/31 ns and Bicompartmental JanusB : 41/94.8 ns) which can be exploited in various applications. Further, the DFT simulations provide the heuristics behind the formation of certain heterostructure with strain and interfacial energies of particular facets dictating the morphology during coupling of QDs.
EM10.02: Oxide-Based Electronics I
Session Chairs
Santanu Bag
Antonio Facchetti
Tse Nga Ng
Monday PM, November 27, 2017
Hynes, Level 1, Room 103
1:30 PM - *EM10.02.01
Improving Contact Resistance in Printed Transistors and Photodiodes
Hyunwoong Kim 1 , Zhenghui Wu 1 , Weichuan Yao 1 , Tse Nga Ng 1
1 , University of California, San Diego, La Jolla, California, United States
Show AbstractPrinting methods to pattern high-mobility thin-film transistors are highly desirable, because they will enable roll-to-roll, high-throughput fabrication of large-area displays and sensors. Amorphous oxide semiconductors have shown promising performance with good uniformity over large-area, and here we patterned thin-film transistors from solution processing of solgel oxide precursors based on In-Ga-Zn nitrates. The initial transistor characteristics are shown to be limited by injection at the inkjet printed contacts; therefore we proceed to use benzyl viologen as a donor dopant to reduce the electrode contact resistance by a factor of 3x. Upon optimization, we have achieved transistor mobility up to 10 cm^2/Vs for IZO annealed at 350°C, and the transistor current changed less than 20% under positive bias stress. We are targeting the integration of transistor and photosensor into sensor arrays for shortwave infrared wavelength. The photodiodes are initially limited by the contact interface, and by tuning the interface with PEIE:ZnO, the dark current is lowered by 10x to realize detectivity up to 10^10 Jones. As the transistor and photodiode components are improved, the devices will be integrated to enable large-area shortwave infrared sensing applications.
2:00 PM - EM10.02.02
Multi-Layer Metal Oxide Transistors Processed via Ultrasonic Spray Pyrolysis
Hendrik Faber 1 , Yen-Hung Lin 2 , Ivan Isakov 2 , Satyajit Das 2 , Thomas Anthopoulos 1
1 , King Abdullah University of Science and Technology (KAUST) , Thuwal Saudi Arabia, 2 Department of Physics and Centre for Plastic Electronics, Imperial College London, London United Kingdom
Show AbstractSolution processable metal oxide (MO) semiconductors have been attracting increasing interest in recent years, leading to their application in a variety of (opto-)electronic devices such as thin-film transistors (TFTs) and integrated circuits, solar cells and memory devices. Research into novel precursor formulations, development of alternative deposition techniques and engineering of post-deposition treatments allowed for great advances in reducing the often required high process temperatures to levels compatible with temperature sensitive and inexpensive substrate materials such as plastics [1].
We previously demonstrated the deposition of ultra-thin (< 10 nm) continuous metal oxide films of e.g. In2O3, ZnO or Ga2O3, via spin coating and low temperature annealing [2-3]. It was shown that TFTs based on layer stacks of bilayer hetero-junctions as well as quasi-superlattice arrangements consisting of up to 5 individual layer stacks, were not limited by the extrinsic mobility of their material constituents but rather by the structural and electronic properties at the MO interfaces [2]. In an effort to transfer these principles to deposition techniques more suitable for large area, high-throughput manufacturing, we demonstrated high performance In2O3/ZnO hetero junction TFTs in which one component (In2O3) was deposited via ultrasonic spray pyrolysis (SP) in ambient conditions and the top layer via spin coating [3]. The computer controlled deposition and fine droplet sizes make SP ideally suited for up-scalability without sacrificing quality.
Here, we extend our early work and report on the fabrication of multilayer TFTs wherein all active channel components are fully formed via spray pyrolysis in ambient atmosphere at low temperatures. The resulting In2O3/ZnO TFTs show remarkable performances with electron mobility values exceeding 50 cm2/Vs and as channel on/off current ratio on the order of 107. The growth kinetics of the individual oxide layers during spray deposition and the impact of solvents will be discussed as well as first insights into bias stability of these high performance devices.
References:
[1] L. Petti, N. Münzenrieder, C. Vogt, H. Faber, L. Büthe, G. Cantarella, F. Bottacchi, T. D. Anthopoulos, G. Tröster, Appl. Phys. Rev. 2016, 3, 21303.
[2] Y.-H. Lin, H. Faber, J. G. Labram, E. Stratakis, L. Sygellou, E. Kymakis, N. A. Hastas, R. Li, K. Zhao, A. Amassian, N. D. Treat, M. McLachlan, T. D. Anthopoulos, Adv. Sci. 2015, 2, 1500058.
[3] H. Faber, S. Das, Y.-H. Lin, N. Pliatsikas, K. Zhao, T. Kehagias, G. Dimitrakopulos, A. Amassian, P. A. Patsalas, T. D. Anthopoulos, Sci. Adv. 2017, 3, e1602640.
2:15 PM - EM10.02.03
NSF SBIR/STTR Program Overview by Debasis Majumdar
Show Abstract3:00 PM - *EM10.02.04
Solution-Processable ZnO Layers for Ultraflexible Organic Photonic Skins
Takao Someya 1 2 , Tomoyuki Yokota 1 , Kenjiro Fukuda 2
1 Electrical and Electronic Engineering and Information Systems, The University of Tokyo, Tokyo Japan, 2 , RIKEN Center for Emergent Matter Science, Saitama Japan
Show AbstractWe report solution-processable ZnO layers for ultraflexible organic photonic skins comprising organic photodetectors (OPDs), and organic light-emitting diodes (OLEDs) that are manufactured on ultrathin plastic film with the thickness of 1 μm [1-4]. In particular, we report recent progress of ultraflexible and conformable, three-color, highly efficient OLEDs and OPDs to realize photonic skins that introduce multiple electronic functionalities such as sensing and displays on the surface of human skin. By integrating green and red OLEDs and OPDs, we fabricated an ultraflexible reflective pulse oximeter.
[1] M. Kaltenbrunner, et al., Nature 499, 458 (2013).
[2] M. S. White, et al., Nature Photonics 7, 811–816 (2013).
[3] M. Kaltenbrunner, et al., Nature Communications 3, 770 (2012).
[4] T. Yokota, et al., Science Advances, Vol. 2, no. 4, e1501856 (2016).
3:30 PM - EM10.02.05
High Speed, Low Voltage, Printed In2O3 Electrolyte-Gated Transistors by Parasitic Capacitance Reduction
Fazel Zare Bidoky 1 , C. Daniel Frisbie 1
1 , University of Minnesota, Minneapolis, Minnesota, United States
Show AbstractPrinted electrolyte-gated transistors (EGTs) have a number of desirable properties including low voltage operation, high ON/OFF current ratio, small negative threshold voltage, and good carrier mobilities. Considering the resolution (L) of a typical printing method like aerosol-jet which is on the order of 10 µm, the highest switching frequency that can be achieved for an EGT is about 107 Hz (µVD/L2, where m is the carrier mobility and VD is applied source-drain voltage). However, the highest reported cut-off frequency for EGT inverters is in the range of 10 kHz. Therefore, the EGT frequency is not limited by semiconductor mobility. We have shown that the frequency is limited by the parasitic capacitance between gate and source/drain. The huge specific capacitance associated with gel electrolyte between gate and source and drain electrodes results in gigantic parasitic capacitance, which causes a huge capacitive current in a dynamic measurement. We have investigated the effect of parasitic capacitance on the dynamic performance of EGTs employing printed In2O3 semiconductor channels. We observed that the capacitive current due to parasitic capacitance scales with electrode dimensions. Finally, we have shown that by removing/reducing gel electrolyte contact with the top of the source/drain electrodes, we can achieve faster switching In2O3 EGTs working up to 100 kHz.
3:45 PM - EM10.02.06
Desing of High-Efficiency Dye-Sensitized Nanocrystaline Solar Cells
Halil Yavuz 1 , Ahmet Macit Ozenbas 2
1 , Yuzuncu Yil University, Van Turkey, 2 Department of Metallurgical and Materials Engineering, Middle East Technical University, Ankara Turkey
Show AbstractNanocrystalline dye sensitized solar cells (DSSC) technology continues to develop as a better alternative to the silicon based solar cells, which are commercialized. This study aims at finding low cost and highly efficient DSSC design and production methods via examination of effects of both photoanode structure and photon-electron generation mechanism on photoanode layers. This will contribute to the commercialization of DSSC technology. Photoanode structure is examined in four groups; transparent conductive glass (TCO), blocking layer (BL), absorber layer (AL) and scattering layer (SL) throughout this study. Firstly, indium doped SnO2 (ITO) was synthesized by sol-gel method for the use in TCO part of the DSSCs. 4.32% conversion efficiency has been found by using those TCO’s in the production of fully sol-gel based DSSCs. For the first time in the literature, 1D ITO structures were synthesized by sol-gel method and this synthesis was used on DSSCs in order to increase the interaction between TCO and AL. However, the commercialized fluorine doped SnO2 (FTO)
TCO’s were used instead of ITO based ones in the rest of the study since their charge transport resistances are lower. ZrO2 BL was found to have superior photovoltaic characteristics in prevention of back transfer reactions. In addition, ZrO2 BL was found to protect the conductivity of FTO based TCO’s during heat treatment. AL, which is responsible for photon to electron generation, was synthesized using 5% Zr doped TiO2 nanoparticles. This synthesis was found to have photon to energy conversion efficiency trice than bare TiO2 absorber layer. Moreover, adding hydrothermal treatment step to the sol-gel method process was found to increase photon to energy conversion efficiency rate. The scattering layers enable to increase the light absorption ability of DSSC via unused photons scattering back to metal oxide sensitized interface. For this purpose, SL was produced by 10% Zr modified TiO2 particles. These particles showed better performance rate than traditionally produced scattering layer. As a result of all these analyses, this Thesis found that the modifications made to the photoanode increased DSSC’s photovoltaic characteristics. After the modifications 7.45% photon to energy conversion efficiency was obtained.
4:00 PM - EM10.02.07
Solution Processed, Sub-2V Electrolyte Gated Transistors with Perovskite Gate Insulator
Kihyon Hong 1 , Jeong Min Kim 1 , Keun Hyung Lee 2 , Juyoung Ham 3 , Jae Yong Park 3 , Jong-Lam Lee 3
1 , Korea Institute of Materials Science, Changwon Korea (the Republic of), 2 Chemical Engineering, Inha University, Incheon Korea (the Republic of), 3 Materials Science and Engineering, Pohang University of Science and Technology, Pohang Korea (the Republic of)
Show AbstractBecause hybrid organic-inorganic perovskites have both semiconductor and electrolyte properties, the materials have great potential for practical applications in energy, electronics, and display technologies. So far their semiconductor properties have been mainly investigated in the solar cells and light emitting diodes: Ion behavior in transistors and light emitting cells is relatively unknown. To probe the electrolyte properties of perovskite film, we fabricate solution processed, elecrolyte gated transistors (EGTs) using metal hallide perovskite gate insulator. The perovskite film reveals electrolyte characteristics with ionic conductivity of 0.05 mS/cm. EGTs formed by the combination of ZnO (channel) and CH3NH3PbI3 (gate insulator) exhibited typical n-type transistor behavior and field-effect mobilitiy of 0.21 cm2/Vs. In addition, the device with PEDOT:PSS channel layer showed abnormal ambipolar characteristic due to the immobile CH3NH3+ cations. This demonstration of EGTs provides an unique electrolyte properties induced by the co-existence of mobile and immobile ions in perovskite. Based on these electrical studies, we attribute formation of electrical double layer induced by mobile I- anions and immobile CH3NH3+ cations in perovskite based EGTs.
4:15 PM - EM10.02.08
Low-Temperature Solution-Processed Oxide Thin-Film Transistors on Flexible Shape Memory Polymer Substrate
Trey Daunis 1 , Gerardo Gutierrez-Heredia 1 , Ovidio Rodriguez Lopez 1 , Jian Wang 1 , Walter Voit 1 , Julia Hsu 1
1 , University of Texas at Dallas, Richardson, Texas, United States
Show AbstractTransparent and flexible thin film transistors (TFTs) have potential applications in growing areas such as displays, radio frequency ID tags, and biomedical devices. Shape memory polymer (SMP) substrates with improved thermal mechanical response add desirable control to the product shape and modulus. Until date, TFTs developed on SMP substrates have been limited to vacuum deposition methods. While TFTs processed through solution-based techniques have achieved device performance close to their vacuum processed counterparts on rigid substrates, they have not yet been demonstrated on SMP substrates due to the required high calcination temperatures (> 500 °C). To fully benefit from the advanced SMP substrates, we report successful demonstration of TFTs with solution-processed aluminum oxide (Al2O3) gate dielectric and indium oxide (InOx) channel on an SMP substrate at temperatures from 150 - 225 °C. Using a UV-activated solution combustion process, Al2O3 and InOx precursor films are patterned by exposing to UV-ozone through a shadow mask. This process eliminates the need for photolithographic patterning using additional photoresist layers and harsh etchant solutions. TFTs fabricated by this method on SMP exhibit a field-effect mobility of 10 cm2/V*s, on/off ratios of 107, and threshold voltages ~ 0V. We will discuss the effects of precursor solution chemistry and calcination temperature on the TFT performance on SMP substrates. To enable low-power CMOS logic, we explore extending this process to the fabrication of TFTs with p-type oxides, e.g. copper chromium oxide (CCO).
4:30 PM - *EM10.02.09
Solution-Processed Inorganics for Electronic and Photonic Device Applications
Antonio Facchetti 1 2
1 , Northwestern University, Evanston, Illinois, United States, 2 , Flexterra, Skokie, Illinois, United States
Show AbstractIn this presentation new approaches to metal oxide (MO) and hybrid materials for unconventional electronic applications are presented. Particularly, we will discuss our latest results in developing amorphous In-W-X-O (W, X = none, Ga, Sn, Zn, Y, La) formulations for combustion synthesis using a combination a coordinating fuel-supporting fuel pairs enabling large thin-film transistor performance for films annealed at temperatures < 300 C. Furthermore, clear correlations between (bulk) heat of combustion and (thin-film) microstructural/charge transport performance are obtained. Furthermore, we demonstrate a new approach to amorphous metal oxide alloys by “doping” metal oxide matrices using electrically insulating polymers such as poly(vinylalcohol) (PVA), poly(vinylphenole) (PVP), and poly(ethylenimine) (PEI). These hybrid polymer-MO compositions exhibit unusual charge transport characteristics where optimal polymer content enables large carrier mobilities (large on-currents) but low off-currents and near-zero turn-on voltages, which is essential for circuit applications. Finally, we will show that some of these ultra-thin MO films finds application as interlayers in organic solar cells.
Symposium Organizers
Santanu Bag, Air Force Research Laboratory
Edward (Ted) Sargent, University of Toronto
Patrick J Smith, The University of Sheffield
Teodor Todorov, IBM T.J. Watson Research Center
Symposium Support
MilliporeSigma (Sigma-Aldrich Materials Science)
NovaCentrix
Strem Chemicals, Inc.
EM10.03: Colloidal Nanocrystal Building Blocks II
Session Chairs
Delia Milliron
Dmitri Talapin
Tuesday AM, November 28, 2017
Hynes, Level 1, Room 103
8:00 AM - *EM10.03.01
Colloidal Nanocrystals for Thin-Film Optoelectronics
Dmitri Talapin 1
1 , University of Chicago, Chicago, Illinois, United States
Show AbstractDevelopment of nanostructured materials has introduced revolutionary approaches for materials processing and electronic structure engineering. These materials can offer the advantages of crystalline inorganic solids combined with inexpensive solution-based device fabrication. Along these lines, semiconductor quantum dots are explored as the functional elements for printable electronics, light emitting devices, photodetectors and solar cells. All these applications require efficient coupling between individual nanostructured components. I will discuss emerging advances in the surface chemistry of semiconducting nanostructures that are poised to enable advances in additive manufacturing of semiconducting and multifunctional materials. Specifically, I will discuss inorganic linkers that permit electronic coupling between the nanocrystals and new semiconducting "solders" that transform to form high-quality inorganic semiconductors. I will also introduce a general chemical approach for photoresist-free, direct optical lithography of functional inorganic nanomaterials (DOLFIN). Examples of patterned materials include metals, semiconductors, oxides, and magnetic and rare earth compositions. No organic impurities are present in the patterned layers, which helps achieve good electronic and optical properties. The conductivity, carrier mobility, dielectric, and luminescence properties of optically patterned layers are on par with the properties of state-of-the-art solution-processed materials. The ability to directly pattern all-inorganic layers using a light exposure dose comparable to that of organic photoresists opens up new opportunities for thin-film device manufacturing.
8:30 AM - EM10.03.02
Solution Processing of Metal Oxide Nanostructures for Plasmonics and Optoelectronics
Enrico Della Gaspera 1 , Joel van Embden 1 , Anthony Chesman 2 , Jacek Jasieniak 3
1 , RMIT University, Melbourne, Victoria, Australia, 2 Manufacturing, CSIRO, Melbourne, Victoria, Australia, 3 Materials Science and Engineering, Monash University, Melbourne, Victoria, Australia
Show AbstractSolution processing is an accessible and versatile approach for synthesising structurally and chemically controlled inorganic nanomaterials. However, for most thin-film optoelectronic applications, the material quality benchmarks are set by expensive vacuum depositions. The ability to control the purity, surface chemistry, and microstructure of solution-processed nanomaterials through the use of tailored reaction chemistry and processing conditions will enable to move away from vacuum-based processes. This will reduce the cost and improve the scalability of nanomaterials synthesis and device fabrication, therefore meeting the increasing demand for cheaper consumer electronics.
In this talk a few strategies to develop metal oxide nanostructures will be presented, along with their applications within various optoelectronic devices. First, the colloidal synthesis of highly doped plasmonic ZnO nanocrystals will be described, focussing on doping strategies, scalability, and on the fabrication of infrared absorbers, transparent electrodes and plasmonic gas sensors. Then the aqueous bath deposition of both intrinsic (semiconductive) and doped (conductive) ZnO thin films will be discussed, highlighting the possibility to achieve the deposition of highly crystalline materials at low temperatures with excellent control on their morphological, structural and optoelectronic properties. The high quality of these thin films will be demonstrated by using them to replace vacuum-processed buffer layers and electrodes within high efficiency solar cells and light emitting devices.
References
E. Della Gaspera, M. Bersani, M. Cittadini, M. Guglielmi, D. Pagani, R. Noriega, S. Mehra, A. Salleo, A. Martucci, J. Am. Chem. Soc., 2013, 139, 3439-3448.
E. Della Gaspera, A. S. R. Chesman, J. van Embden, J. J. Jasieniak, ACS Nano, 2014, 8, 9154-9163.
E. Della Gaspera, D. F. Kennedy, J. van Embden, A. S. R. Chesman, T. R. Gengenbach, K. Weber, J. J. Jasieniak, Adv. Funct. Mater., 2015, 25, 7263-7271.
M. Sturaro, E. Della Gaspera, N. Michieli, C. Cantalini, S. M. Emamjomeh, M. Guglielmi, A. Martucci, ACS Appl. Mater. Interfaces, 2016, 8, 30440-30448.
8:45 AM - EM10.03.03
Low Temperature Synthesis of Germanium-Based Nanorods and Nanowires
Patrik Pertl 1 , Michael Seifner 1 , Alois Lugstein 2 , Sven Barth 1
1 Institute of Materials Chemistry, Vienna University of Technology, Vienna Austria, 2 Institute of Solid State Electronics, Vienna University of Technology, Vienna Austria
Show AbstractSemiconductor nanowires are very promising building blocks for devices and at the same time ideal model systems to study materials properties. Germanium and Ge-based nanowires and nanorods have a broad spectrum of potential applications including electronic and optoelectronic devices, lithium ion batteries, sensors etc. The synthesis of these anisotropic nanostructures usually requires temperatures >300 °C hampering the growth on temperature-sensitive materials such as polymers.
We present the growth of highly crystalline Ge as well as Ge1-xSnx nanowires and nanorods at temperatures below 200 °C. These structures can be grown either via the solution-liquid-solid (SLS) or the vapor-liquid-solid (VLS) mechanism depending on the growth conditions. In addition, we can show that the slow growth of these structures at low temperatures is due to the precursor decomposition characteristics as a limiting factor. Moreover, the decomposition of the Ge precursor is catalyzed by the presence of Ga seeds since no decomposition products are obtained in their absence. The nanowires have been characterized by different analytical methods including TEM, EDX as well as XRD and the incorporation of unusually high Ga contents of up to 3% [2] and also high Sn contents of up to 20% in the Ge structures has been observed. Unusually high catalyst incorporation in group IV nanowires has been observed for other semiconductor/metal combinations and helped targeting metastable compositions [3]. Therefore, electrical characterization of individual Ge-based nanowires has been performed in order to quantify the impact of the heteroatom incorporation on their conductivity. In addition, the thermal stability has been investigated in XRD studies.
[1] S. Barth, F. Hernandez-Ramirez, et.al. Prog. Mater. Sci. 2010, 55, 563.
[2] P. Pertl, M.S. Seifner, A. Lugstein, S. Barth, manuscript submitted.
[3] M. S. Seifner, F. Biegger, A. Lugstein, J. Bernardi, S. Barth Chem. Mater. 2015, 27, 6125.
9:00 AM - EM10.03.04
Multicolor Upconverting Lasers Using Lanthanide-Doped Nanocrystals in Microcavity Resonators
Angel Fernandez-Bravo 1 , Kaiyuan Yao 1 , Edward Barnard 1 , Nicholas Borys 1 , Cheryl Tajon 1 , Bining Tian 1 , Emory Chan 1 , Bruce Cohen 1 , P James Schuck 1
1 , Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show Abstract
Rare earth upconverting nanoparticles (UCNPs) enable ultra large anti-Stokes shifts by multiphoton absorption with relatively sharp emission and long excited-state lifetimes, leading to a variety of applications from background-free bio-labels to sub-bandgap sensitizers in next-generation photovoltaics. Historically, upconversion processes required higher excitation fluences than downconversion processes, which have hindered a more general applicability in many fields, i. e. photovoltaics, deep-tissue imaging or optogentics. Photon upconversion in these materials is mediated by long-lived intermediate states that undergo optical excitation followed by subsequent energy transfer (ET) and/or excited state absorption (ESA). By tuning the lanthanide composition and concentration, the complex interplay of these processes can be systematically manipulated and optimized. In this work, core-shell nanocrystals following the general structure NaYF4:Yb/Er:NaYF4 have been used with different lanthanide ion doping concentrations. Solution processed loading of nanocrystals to polystyrene spherical microcavities are used to achieve gain and lasing of the upconverted emission via the excitation of whispering gallery modes (WGM). Optical coupling into resonators can be achieved by placing nanocrystals onto the surface of a microbead in the vicinity of the evanescent field in such a way that the pumping as well as upconverted photons can resonate inside the cavity a number of cycles concurring in light amplification. The lasing threshold and optical gain is found to sensitively depend on the concentration of lanthanides in the crystal lattice and through optimization, upconverted lasing in the visible frequencies has been achieved in microsized beads loaded with nanocrystals with thresholds as low as 1 µW cm-2 under pulsed excitation. We leverage the low threshold to produce the first upconverting microlasers that are pumped under continuous-wave (CW) excitation. The demonstration of CW light amplification in these UCNP-microcavity architectures may enable the broad functionality of UCNPs for background free imaging, theranostics, volumetric displays, waveguides and photonics structures.
9:15 AM - EM10.03.05
Nanometer Scale Imaging of Ligand Exchanged PbSe Quantum Dot Superlattices
Adam Moule 1 , Fei Wu 1 , Xiaolei Chu 1 , Alex Abelson 2 , Caroline Yu Qian 3 , Matt Law 2 3
1 , University of California, Davis, Davis, California, United States, 2 Department of Chemistry, University of California, Irvine, Irvine, California, United States, 3 Department of Chemical Engineering, University of California, Irvine, Irvine, California, United States
Show AbstractOrdered PbS and PbSe quantum dot arrays have demonstrated multiple exciton generation in response to photo excitation by high energy photons. This inherently quantum material demonstrates a pathway to photovoltaic efficiency above the Shockley limit if ordered and defect free super-lattices of these nanoparticles can be fabricated. Here we use high-resolution tomographic imaging of PbSe super-lattices to study the material order resulting from self-assembly and ligand exchange. Quantum dot arrays are synthesized and self-assembled using long chain ligands to ensure a narrow size distribution and assembly into ordered arrays. After the layer has formed, in-situ ligand exchange is used to reduce the distance between quantum dots, leading to recrystallization of the super-lattice, order/disorder transitions, and defect formation. The super-lattice order seen at the top interface of the material and accessible by SEM or TEM imaging is often very different from the arrangement of particles in the center of self-assembled films. We use tomographic reconstruction of STEM images to determine the position of quantum dots with nm precision and study the effect of specific processing techniques, ligands, and solvents on defect formation.
10:00 AM - *EM10.03.06
Transparent Conductive Films from Doped Metal Oxide Nanocrystals
Delia Milliron 1
1 , The University of Texas at Austin, Austin, Texas, United States
Show AbstractSynthetic control over colloidal metal oxide nanocrystals has advanced so that aliovalent dopants can be introduced, producing degenerately doped semiconductors, such as indium tin oxide, with metal-like optical properties. Thin films processed from solvent dispersions of such nanocrystals are highly transparent, since the nanocrystal dimensions are well below the wavelength of light and their ultraviolet band gap energies preclude visible light absorption. However, such films have typically been poorly conducting, even when the nanocrystals contain a high density of free electrons, as deduced from their optical properties. Poor conductivity persists even after removing insulating ligands by chemical and thermal processing. Intriguingly, the conductivity is improved by orders of magnitude following in-filling of aluminum oxide (an insulator) by atomic layer deposition. The electronic characteristics of such composite films are analyzed by variable temperature conductivity measurements. Furthermore, fully solution processed composites are demonstrated by in-filling with a sol gel process. The resulting films have highly competitive electronic and optical properties and exceptionally high carrier mobilities, which we ascribe to their nanostructured nature.
10:30 AM - EM10.03.07
Enhanced Device Lifetime of Double-Heterojunction Nanorod Light-Emitting Diode
Seong-Yong Cho 1 , Nuri Oh 1 , Sooji Nam 1 , Yiran Jiang 1 , Moonsub Shim 1
1 , University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractBright, size-tunable, narrow bandwidth emission and the solution processability of colloidal quantum dot light-emitting diodes (QD-LEDs) are highly promising for developing next generation optoelectronics and displays. Varying composition and/or shape of QDs can improve device performance and impart new capabilities. For example, introduction of double heterostructure within nanorod emitters for QD-LEDs can allow enhanced charge injection/extraction as well as optical anisotropy and recently, we have shown that double-heterojunction nanorod (DHNR) LEDs are multifunctional devices that can both emit and detect/harvest light. While there is much excitement with these capabilities that can lead to breakthroughs in multiple areas include novel interactivity with displays, device-to-device communications, and energy scavenging, there is very little knowledge on the long-term stability of and failure mechanisms in DHNR- and QD-LEDs. Before implementation of these devices into consumer products, such knowledge is absolutely essential. Here, a comparative study on accelerated device lifetime of DHNR- and core/shell (C/S) QD-LED will be presented. A common dependence of device lifetime on the initial driving voltage observed is independent of the initial luminance and independent of whether the emitting materials are DHNRs or QDs prepared under different conditions. Reducing the hole injection barrier by doping the hole transport layer or by altering emitter band structure (as is done with DHNRs) allows lower voltage operation, leading to longer device lifetimes. Hole accumulation/trapping leading to the degradation of organic hole transport layer, which in turn deteriorates electroluminescence but not the photoluminescence of the emitting layer, is suggested to be the main cause of degradation in these devices.
10:45 AM - EM10.03.08
Polarized Optical Metamaterials Based on Perovskite Supramolecular Nanocomposites via Direct Ink Writing
Nanjia Zhou 1 4 , Yehonadav Bekenstein 2 , Carissa Eisler 2 3 , A. Paul Alivisatos 2 3 , Jennifer Lewis 1 4
1 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States, 4 Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, Massachusetts, United States, 2 Department of Chemistry and Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, California, United States, 3 Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractOne-dimensional (1D) nanomaterials with highly anisotropic optoelectronic properties are key components in applications including energy harvesting, flexible electronics, and biomedical imaging. A three-dimensional (3D) patterning method to precisely assemble these nanomaterials with controlled spatial composition, arrangement and orientation, would enable the direct translation of the nanomaterial properties to macroscale structures. Using brightly emitting colloidal cesium lead halide perovskite (CsPbX3, X = Cl, Br, and I) nanowires as a model system, we developed new nanocomposite inks composed of these nanowires suspended in block copolymer solutions. Using direct ink writing, we can programmably control nanowire alignment within these polymeric matrices. Exploiting this capability, we produced photonic nanocomposites that exhibit highly polarized absorption and emission properties. We will highlight our efforts to fabricate and characterize polarized photonic metamaterials for several applications, including optical imaging, encryption, data storage, sensing, spectrum splitting, and full-color display.
11:00 AM - EM10.03.09
Rationally Designed Nanocrystal Precursors for the Co-Assembly of Titania Inverse Opals
Katherine Phillips 1 , Tanya Shirman 1 , Joanna Aizenberg 1
1 , Harvard University, Cambridge, Massachusetts, United States
Show AbstractA number of optical, chemical, and sensing applications are enabled by defect-free inverted colloidal crystals, and the properties of these inverse opal structures are further expanded by controlling their composition. High-quality, crack-free silica inverse opals with minimal defects can be self-assembled using colloidal crystallization in the presence of a sol-gel precursor; however, this co-assembly process remains challenging for transition metal oxide inverse opals. Here, we describe how to assemble highly ordered, crack-free inverse opals by controlling the state of the matrix precursor, using the synthetic conditions of transition metal oxide nanocrystals to control their surface charge and crystallinity. We focus on titania while also extending the process to other metal oxides, and we expect that this strategy can be further extended to additional oxides and other material classes as well as to other structures.
11:15 AM - EM10.03.10
Solution Processed InAs Nanowire Transistors for Microwave Reconfigurable Circuits
Maxim Shkunov 1 , Bobour Mirkhaydarov 1 , Haris Votsi 1 , Peter Aaen 1 , Paul Young 2 , Philippe Caroff 3 4
1 , University of Surrey, Guildford United Kingdom, 2 School of Engineering and Digital Arts, University of Kent, Canterbury United Kingdom, 3 , University of Cardiff, Cardiff United Kingdom, 4 Department of Electronic Materials Engineering, The Australian National University, Canberra, Australian Capital Territory, Australia
Show AbstractSolution processed semiconducting nanowires demonstrate excellent potential for printed electronics applications including flexible circuits and displays, chemical and biological sensors and energy harvesters, due to efficient, low-temperature, large-area deposition of functional nanowire inks. Nanowire FETs, being some of the main building blocks for these applications, typically have relatively high impedances of tens to a few hundred kOhms even when they are fully switched on. Novel applications of nanowire FETs proposed for reconfigurable microwave circuits demand drastically lower impedances of only 50 Ohms to allow low-loss integration with microwave lines. The challenge of low FET impedance cannot be met with low mobility semiconducting nanowire materials, including Si and ZnO.
In this work, we investigate solution-processed high mobility InAs nanowires as active channels in NW-FETs, targeting reconfigurable microwave antenna applications, where each transistor operates as a switch to turn on and off various parts of the antenna structures to change its frequency, radiation pattern or polarisation. To manipulate InAs nanowire deposition from solutions, dielectrophoresis technique is applied to orient and to position nanowires between source-drain transistor electrodes.
Proof of principle InAs NW FETs microwave switches are demonstrated as fully integrated parts of the transmission line in coplanar waveguide geometry, with FET on-resistance close to 50 Ohms. The FETs allow efficient switching between on and off states with DC modulation ratio of ~1000. Microwave nanowire FETs response is measured up to 30 GHz and S-parameters are extracted. Difference in insertion loss |S12| between the switch on and off states is ~10 dB. The application of the InAs nanowire FET switches is also demonstrated in reconfigurable offset-open geometry, thus representing a building block for the matching circuits for reconfigurable antennas.
We further discuss prospects of nanowire FETs for printable microwave circuit applications.
11:30 AM - EM10.03.11
Engineering Active Nanodevices with Nanometer Precision and Surface Uniformity
Farnaz Niroui 1 , Jatin Patil 1 , Jeffrey Lang 1 , Vladimir Bulovic 1
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractApproaching dimensions in the few-nanometer regime can lead to active devices of unique functionalities but is challenging to achieve due to limitations in processing techniques. Conventional top-down fabrication lacks the desired precision and resolution which causes imperfections on the order of the device critical dimensions leading to undesired performance. At such small dimensions, this challenge is ever more restrictive when involving mechanically reconfigurable components – where failure due to dominant surface adhesive forces is prevalent. To overcome this challenge and enable electrically and electromechanically-active devices only a few nanometers in dimensions with nanometer precision and uniformity over large areas, we complement top-down fabrication with bottom-up directed assembly of solution-processed nanostructured building blocks. In this approach, directed assembly is achieved through engineering of surfaces and interfaces such that building blocks can arrange into a desired architecture in response to a locally induced force control. This is further assisted by external stimuli including selective chemical interactions, physical guides and electric fields to enable complex asymmetric features by deterministic positioning of the components. To ensure the devices can be electrically and electromechanically activated, this bottom-up assembly is complemented by top-down fabrication of electrical interconnects modified through a surface planarization technique. Collectively, through this integrative fabrication approach, electromechanically-active nanostructures with features < 10 nm and with < 1 nm surface uniformity are reproducibly formed. As an example application, we have developed tunneling-based nanoelectromechanical switches that can overcome the challenges of conventional counterparts towards achieving more energy-efficient performance.
11:45 AM - EM10.03.12
Solution-Phase Ligand Exchange for Lead Chalcogenide Quantum Dots Allows Single-Step Casting of Thick Conductive Films
Jeffrey Pietryga 1 , Qianglu Lin 1 , Hyeong Jin Yun 1 , Tom Nakotte 2 1 , Victor Klimov 1
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 , New Mexico State University, Las Cruces, New Mexico, United States
Show AbstractThe use of semiconductor nanocrystal quantum dots (QDs) in electronic and optoelectronic devices is immensely promising from both a cost and performance standpoint. However, often overlooked in this analysis is necessity of post-synthetic chemical surface treatments to enhance electronic coupling between QDs and allow for efficient charge transport in QD films. This is not a trivial detail, as the most effective surface treatments are often performed only after the QDs are already substrate-bound, and only on very thin layers of QDs (~20 nm or less): thicker layers require numerous, laborious deposition steps. To really reap the benefits of solution processing in roll-to-roll processing, such as by using spray, ink-jet or knife-edge deposition techniques, single-step deposition of conductive QD films is required. This has driven the development of in-solution ligand-treatment techniques for a range of QD materials. However, despite their importance in solar cells and infrared (IR) light-emitting diodes and photodetectors, advances in these chemical treatments for lead chalcogenide (PbE, where E = S, Se or Te) QDs have lagged dramatically behind. In this talk, we present a method for fast and effective ligand exchange for PbE QDs in solution, resulting in QDs completely passivated by a wide range of small anionic ligands. Due to electrostatic stabilization, these QDs readily form stable, concentrated dispersions in polar solvents. QDs of all three Pb chalcogenides retain their photoluminescence, allowing for a detailed study of the effect of the surface ionic double layer on electronic passivation of QD surfaces, which we find can be explained using the hard/soft acid–base theory. Importantly, we prepare highly conductive films of PbS, PbSe, and PbTe QDs by directly casting from solution without further chemical treatment, as determined by field-effect transistor measurements. This method allows for precise control over the surface chemistry, and therefore the transport properties of deposited films. It also permits single-step deposition of films of unprecedented thickness via continuous processing techniques, as we demonstrate by preparing a dense, smooth, 5.3-μm-thick PbSe QD film via knife-edge deposition. As such, it offers important advantages over laborious layer-by-layer methods for solar cells and photodetectors, while opening the door to new possibilities in ionizing-radiation detectors, which we demonstrate in preliminary studies.
EM10.04: Emerging Materials and Approaches for Light Management
Session Chairs
Tuesday PM, November 28, 2017
Hynes, Level 1, Room 103
1:30 PM - *EM10.04.01
Emerging Earth-Abundant Chalcogenide-Based Semiconductors for Thin-Film Photovoltaics
David Mitzi 1
1 , Duke University, Durham, North Carolina, United States
Show AbstractThis talk addresses several promising emerging thin-film PV technologies based on earth-abundant Cu-Zn-Sn-S-Se (CZTS), Cu-Ba-Sn-S-Se (CBTS) and related chalcogenide-based absorbers,1,2 and relatively simple solution- and vacuum-based film deposition processes that enable the fabrication of high-performance absorber layers, with resulting device sunlight-to-electricity power conversion efficiencies (PCEs) exceeding 12% for CZTS and 5% for CBTS. Key focal points for the talk will include developing film deposition pathways and precursors (especially solution-based), as well as understanding defects and limiting characteristics of the resulting PV devices. For the CZTS system, the close chemical similarity between, for example, Cu and Zn promotes anti-site disorder within the films, contributing to reduced device open circuit voltage. In CBTS, the much larger Ba ion, occupying a site that has 8-fold coordination rather than 4-fold (as for Cu, Zn and Sn in CZTS), reduces the probability of anti-site disorder. Although at an early stage of development (i.e., for CBTS), the concept of employing atomic size discrepancy in conjunction with differences in atomic coordination for limiting anti-site disorder offers a pathway for overcoming performance issues encountered within complex multinary chalcogenide semiconductors.
1. D. Shin, B. Saparov, T. Zhu, W. P. Huhn, V. Blum, D. B. Mitzi, Chem. Mater. 28, 4771 (2016).
2. D. Shin, B. Saparov, D. B. Mitzi, Adv. Energy Mater. 7, 1602366 (2017).
2:00 PM - EM10.04.02
Multilayer Photonic Structures Toward Novel Light and Heat Management Devices
Stefan Bachevillier 1 , Hua-Kang Yuan 1 , Jan Gebers 3 , Andreas Hafner 3 , Paul Stavrinou 4 1 , Natalie Stingelin 2 1
1 , Imperial College London, London United Kingdom, 3 , BASF Schweiz AG, Basel Switzerland, 4 , University of Oxford, Oxford United Kingdom, 2 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractPrinted electronic and photonic devices have drawn increasing interest during the last decade due to their promise to allow reducing device production cost and energy consumption during manufacturing. However, the realisation of novel solution-processed technologies requires the targeted development of new, versatile and smart materials that combine the often-superior properties of inorganics with the straight-forward, low-cost fabrication features of ‘plastics’. Here, we will present a novel, printable inorganic-based ink designed for high-throughput fabrication of complex photonic architectures for light- and heat management purposes. The refractive index of our ‘ink’ is highly tunable enabling precise control of its refractive-index contrast with other materials (0.01 < Δn < 0.5) without compromising transparency. Indeed, our materials are of rather exceptional low optical loss as we will demonstrate here. Our system also allows fast and simple patterning by various methods including straightforward thermal or chemical post-processing. We will, for example, demonstrate planar refractive index patterns comprising four different regions that are locally and optically defined from the out-set. This capability enables room-temperature fabrication of patterned photonic devices using only printing techniques and that are compatible with flexible substrates. Similar approaches towards the printing of highly efficient photonic multilayer structures and their integration to devices will also be discussed.
2:15 PM - EM10.04.03
Solution-Processed Waveguides for Light Harvesting
Hua-Kang Yuan 1 , Stefan Bachevillier 1 , Paul Stavrinou 2 1 , Natalie Stingelin 3 1 , Andreas Hafner 4 , Jan Gebers 4
1 , Imperial College London, London United Kingdom, 2 , University of Oxford, Oxford United Kingdom, 3 , Georgia Institute of Technology, Atlanta, Georgia, United States, 4 , BASF, Basel Switzerland
Show AbstractLight capture and transportation is a fundamental part of many technology platforms, including solar. Hence, developments in light guiding beyond fibre optics would accelerate advances in solar energy device integration and a diversification of system architectures. We present a method for fabricating planar or channel waveguides, processed entirely from solution. The high index material we used for this purpose is an inorganic based ink displaying excellent optical properties, including low optical loss. Its refractive index reaches 1.9 and – most importantly— is tunable on a continuous scale, even after film formation. We demonstrate integration of this ink with embossed diffraction gratings for the coupling of light and show that channel waveguides of relatively large dimensions (width in the millimeter- and length in the centimetre length scale) can be formed by local annealing to pattern the refractive index. Maintaining an unrestricted 2-dimensional geometry thereby promotes facile device integration. We discuss how the refractive indices of each material were individually characterised by fitting transmittance spectra to transfer matrix method calculations, explain how finite-element method models and optical measurements were used to elucidate the waveguide optical modes, and discuss future opportunities towards more complex architectures, in e.g. solar energy harvesting applications.
3:00 PM - *EM10.04.04
Solution Processed Double Perovskite Single Crystals for Visible Light and X-Ray Detection
Jiang Tang 1 , Guangda Niu 1 , Weicheng Pan 1 , Haodi Wu 1 , Jiajun Luo 1
1 , Huazhong University of Science and Technology, Wuhan China
Show AbstractHybrid lead halide perovskites have astonished the field of solution processed solar cells due to their soaring device efficiency; they also demonstrated outstanding device performance for visible as well as high energy radiation sensing. These materials, unfortunately, contain highly toxic lead in a water soluable form. It would be of great significance to find lead-free alternatives with comparable device performance. Here we will report our recent progress in using solution processed, all-inorganic double perovskite single crystals (SCs) for visible light and x-ray sensing. More specifically, Cs2AgBiBr6 SCs are grown from aqueous solution with optimized precursor concentration and evaporation speed, and then Au electrodes are deposited after a careful surface rinse. As-prepared SCs possess a decent carrier mobility of ~3 cm2/Vs and a low trap density of ~109 cm-3.Despite their indirect transition nature, as-prepared Cs2AgBiBr6 SC photoconductive photodetectors achieve an impressive dectivity of 1.6x1013 Jones and 3dB bandwith of 1300 Hz. More interestingly, thanks to the high atomic number and suppressed dark current, our Cs2AgBiBr6 SC showed excellent sensitivity towards 30 keV X-rays : the peak sensitivity was 3276 µC Gy air -1 cm–2,and the minimum detectable dose rate was down to 7.2 nGyair s-1, even better than the best value reported for lead based perovskite X-ray detectors.
3:30 PM - EM10.04.05
High Performance Low Temperature Polycrystalline Silicon Thin-Film Transistor Fabricated by Solution-Processed Metal-Induced Lateral Crystallization
Hee Jae Chae 1 , Seung Ki Joo 1
1 , Research Institute of Advanced Materials (RIAM) and Department of Materials Science and Engineering, Seoul National University, Seoul, SE, Korea (the Republic of)
Show AbstractLow-temperature polycrystalline silicon (LTPS) thin-film transistors (TFTs) have been studied intensively for display applications, because they can be integrated in peripheral circuits and show high electrical properties. Among the many types of LTPS methods, the metal-induced lateral crystallization (MILC) has many advantages, including low cost batch process, smoother surface, higher degree of crystalline uniformity, etc. In this work, we developed a novel metal induced lateral crystallization (MILC) method using Ni solution on a large area glass substrate. With the solution-processed MILC (SMILC), the amount of Ni contaminations, located in randomly formed grain boundary which degrades the electrical characteristic of the polycrystalline Si (poly-Si) TFT by creation of potential barrier, could be controlled. The highly densed Ni solution was prepared from 180g of nickel(II) nitrate hexahydrate (Ni(NO3)26H2O), obtained by dissolving Ni in 60% of nitric acid and drying, dissolved in 30ml of deionized water at 70oC. The solution was spin-coated with the speed of 300 RPM on the active layer patterned with photoresist to exposure only the source and the drain region. After spin-coating process, only gel-type nickel(II) nitrate hexahydrate remained. The initial stage of interfacial reaction between amorphous silicon (a-Si) and Ni was examined with the Fourier transform infrared, and we could confirm that the reaction begins over 160 oC. Therefore, the sample was heat-treated on a hot-plate at 180oC to make reaction of Ni on a-Si surface in short time. After that, the sample was cleaned with photoresist stripper using sonication for 10min and rinsed in de-ionized water. Then, SMILC poly-Si was produced from heat-treatment of 550 oC in a vacuum furnace for 2 hours. During the heat process, the low density of Ni and Si compounds transform to NiSi2 as a catalyst, and the migration of NiSi2 triggers phase transition of a-Si toward channel area and generate poly-Si. The growth of poly-Si from the low density of Ni silicide seeds were exhibited from the optical microscope images after 1hour heat-process and SMILC poly-Si is found to have better qualities with wide and long grains than that of MILC poly-Si from the scanning electron microscope images. The transfer curve of the TFT fabricated with SMILC shows superior electrical characteristics such as field-effect mobility, threshold voltage, subthreshold slope, and on/off current ratio. Moreover, reduced defects in channel improved pinning and leakage current, which is the main problem of MILC process. The SMILC process can be adopted easily on a large area substrate without additional equipment, and avoid the plasma damage on a-Si layer from sputtering system. Therefore, its application to the mass production of display is expected to have a substantial impact on the industry.
3:45 PM - *EM10.04.06
Nanotemplates for Effective use of Solar Spectrum
Minwoo Nam 1 , Doo-Hyun Ko 1
1 , Kyung Hee University, Yongin Korea (the Republic of)
Show AbstractThe conversion and manipulation of light via lanthanide-based upconversion (UC) and downshifting (DS) show promise in numerous applications. We demonstrate the lanthanide-doped nanotemplates to improve conversion of ultraviolet and near-infrared to visible light through resonant-mode excitation. The templates are fabricated using nanoimprint technique wherein ordered arrays of nanoscale features are readily made over large areas. The practical applicability of this platform in photovoltaic devices is evaluated, showing distinctively enhanced efficiency. The material-agnostic nanopatterning methodology is further extended to nanopattern CuInGaS2 (CIGS) thin films synthesized by a sol-gel-based solution to achieve simultaneous photonic and electrical enhancements in thin film photovoltaic devices.
4:15 PM - EM10.04.07
Solar Cells of Cubic Structured SnS-SnSe-PbSe Thin Films Produced by Chemical Deposition
Ana Karen Peñaloza 1 , Victoria Elena Gonzalez-Flores 1 , Enue Barrios Salgado 1 , M.T. Santhamma Nair 1 , P.Karunakaran Nair 1
1 , Universidad Nacional Autonoma de Mexico, Temixco Mexico
Show AbstractDuring 2015-17 cubic structured SnS and SnSe (CUB) nanocrystals and thin films prepared by chemical methods have been reported with optical bandgaps (Eg) of 1.7 and 1.4 eV (direct), respectively. These Eg are much higher than 1.1 eV (indirect) of their more popular orthorhombic (ORT) polymorphs. In experimental and theoretical studies, the cubic polymorphs have been found to possess thermal stability at temperatures up to 400 oC, comparable with that of their ORT polymorphs. The peculiarity of the CUB-polymorph is the large unit cell with edge 11.58 Å (SnS-CUB) and 11.93 Å (SnSe-CUB), the latter nearly double that of PbSe (6.15 Å). The Eg of chemically deposited PbSe thin films are susceptible to considerable increase (toward 1 eV) compared with bulk crystalline value (0.36 eV). We present in this work the development of solar cell structures on fluorine-doped SnO2 films (FTO) of: FTO/CdS (100 nm)/SnS-CUB (120-240 nm)/SnSe-CUB(60-240 nm)/PbSe(40-120 nm)/C-Ag. All the films are produced by sequential chemical deposition. Preliminary results at this time are modest – open circuit voltage of 350 mV current density 1 mA/cm2. However, we consider that this is an ideal system to work with because of the graded Eg of 1.7 – 1.4 – 1 eV available in the system, which can profitably absorb most part of the solar radiation with predicted light generated current density above 35 mA/cm2 for the film thicknesses mentioned. Post deposition heat treatments have been reported in 2016 to produce considerable modification of electrical conductivity in SnS-SnSe-CUB stacks. The electrical conductivity and Eg of PbSe deposited from a chemical bath containing lead nitrate, selenosulfate and small amount of thiourea are modified with deposition temperature 30-60 oC, and further through post-deposition annealing in Se-ambient at 300 oC. We present the basic material properties as well as of these solar cell structures.
4:30 PM - *EM10.04.08
Molecular Ink-Derived Earth-Abundant Chalcogenide Materials for Photoelectrochemical Water Splitting
Wooseok Yang 1 , Jihoon Ahn 1 , Yunjung Oh 1 , Jeiwan Tan 1 , Hyungsoo Lee 1 , Jaemin Park 1 , Jooho Moon 1
1 , Yonsei University, Seoul Korea (the Republic of)
Show AbstractPhotoelectrochemical (PEC) water splitting has drawn significant attention as a cost-effective approach to accomplish solar hydrogen production because photoelectrode in PEC device simultaneously functions as a light harvester and electrolysis. In order to reduce the cost of solar hydrogen, earth-abundant light absorber materials should be accomplished with low-cost solution processing. In this talk, we will give a brief overview of recent progress in solution-processed photocathodes with earth-abundant constituents. Among the emerging photocathode materials, antimony selenide (Sb2Se3) is an attractive one due to the narrow band gap of 1.0 – 1.3 eV, high absorption coefficient (>105 cm-1) and high hole mobility. Moreover, Sb2Se3 is simple binary compound only having a thermodynamically stable orthorhombic phase, which allows avoiding the complexity of phase and defect control as encountered in other low-cost p-type semiconductor. We fabricated shape-controlled Sb2Se3 nanostructures via a facile spin-coating with molecular inks. The underlying unique growth mechanism of Sb2Se3 nanostructures was elucidated based on understanding of molecular chemistry. The molecular inks were derived from mixtures of thiol-amine, so-called “alkahest”, which have been known as a strong solvent system capable of dissolving diverse compound including metals, oxides and chalcogenides. High-quality metal chalcogenides were obtained by sequential coating molecular solution and annealing. With the controlled shaped Sb2Se3 nanostructures, the subsequent deposition of TiO2 and Pt enabled us to demonstrate an unprecedentedly enhanced performance, reaching a 12 mA cm-2 at 0 V vs reversible hydrogen electrode (RHE) under AM 1.5 G illumination.
EM10.05: Poster Session I: Oxides
Session Chairs
Wednesday AM, November 29, 2017
Hynes, Level 1, Hall B
8:00 PM - EM10.05.01
Rapid Fabrication of Solution-Processed Metal Oxide Transistors via Photonic Processing at Room Temperature
Anna Regoutz 1 , Kornelius Tetzner 1 , Yen-Hung Lin 1 , David Payne 1 , Thomas Anthopoulos 2
1 , Imperial College London, London United Kingdom, 2 , King Abdullah University of Science and Technology, Saudia Arabia (KAUST), Thuwal Saudi Arabia
Show AbstractMetal oxide semiconductors (MOSs), including e.g. In2O3 and ZnO, have received great attention over recent years due to their excellent electrical and optical properties. The array of possible synthetic routes to produce high quality thin films of these MOSs, including solution processing, make them highly promising for low-cost manufacturing of (opto-)electronic devices and circuits. Solution processing of these oxides allows high-throughput deposition on large areas using inexpensive techniques such as printing and spray coating, make them ideal candidates for large area applications, e.g. flat screen displays. Although the combination of MOSs with solution-based processes has many attractive characteristics, a major limitation is that high curing temperatures are necessary to achieve good quality films. This poses an issue for flexible substrates, e.g. plastic, and for rapid production. An alternative to established annealing processes is the use of high power xenon flash lamps for rapid conversion of the precursors.
This work presents a rapid fabrication protocol based on the combination of solution-based deposition and photonic curing for MOS field-effect transistors based on In2O3 and In2O3/ZnO heterostructures. The photonic processing is extremely rapid with processing times less than 18 seconds. The resulting thin-film transistors have low operating voltages (≤ 2 V) and field-effect mobilities of up to 35 cm2/Vs. A particular focus of the work likes on the structural and electronic properties as well as the changes in surface chemistry of the MOS films before and after photonic curing. All results are benchmarked against traditional annealing procedures. In particular, X-ray photoelectron spectroscopy (XPS) is employed to follow changes in the films occurring during photonic curing. XPS is a method used widely in the solid-state and surface sciences and provides a unique combination of qualitative and quantitative information concerning the surface chemistry, elemental composition, and electronic structure. In addition, it is extremely surface-sensitive and non-destructive.
Core level spectra, including In 3d, Zn 2p, and O/C/N 1s, are used to study the oxidation states of In and Zn as well as the chemical environments of C, O, and N. The conversion from the precursors used in solution processing to the high-quality oxide films can be followed in detail both qualitatively and quantitatively. Furthermore, valence band (VB) spectra are used to study the electronic structure of the thin film structures. Clear changes between thermally annealed and photonically cured films are observed.
Ultimately, this work shows the immense potential of solution-processed MOSs for low-cost, high-throughput, and at the same time high-quality devices. The capability of XPS measurements to follow chemical reactions taking places within solution-processed thin film device stacks is particularly helpful to understand the resulting device behaviour.
8:00 PM - EM10.05.02
Photochemical Activation of Solution-Processed Dielectric Functional Thin Film with Oxozirconium Methacrylate Cluster—Zr6(OH)4O4(OMC)12
Joohyung Park 1 , Myunggil Kim 1
1 , Chung-Ang University, Seoul Korea (the Republic of)
Show AbstractOrganic-inorganic hybrid materials show a complementary character which originates from each organic and inorganic part. Among various kinds of molecules for hybrid materials, we investigate electronic properties of oxozirconium cluster thin film fabricated by solution-process, especially Zr6(OH)4O4(OMc)12 (OMC: methacrylate) molecule which has metal-oxo core capped with polymerizable functional group. The metal oxo core structure is well defined core structure yet, globally it is polymerized and amorphous phase. Here we adopt the molecule which shows a coexistence of two immiscible phase and investigate electronic properties for an electric insulator such as AC dielectric constant and leakage current density. With various polymerization conditions, including addition of photo-initiator, photochemical polymerization and thermal polymerization, material activation occurs at near room temperature. Especially, photochemical activation demonstrated leakage current density at 2MV/cm be 4.44x10-7A/cm2 and AC dielectric constant at 100kHz be 4.246. Maxwell-Garnett theory of dielectric mixture indicates that Zr6 cluster’s geometry and dielectric properties of organic and inorganic parts match with measured dielectric constants.
8:00 PM - EM10.05.03
Effect of UV/Ozone Treatment on Self-Aligned InZnO Thin-Film Transistors towards an All-Solution Process
Chaiyanan Kulchaisit 1 , Juan Paolo Bermundo 1 , Mami Fujii 1 , Yasuaki Ishikawa 1 , Yukiharu Uraoka 1
1 , Nara Institute of Science and Technology, Nara Japan
Show AbstractElectronic devices using amorphous oxide semiconductor (AOS) have been emerging in next generation displays because AOS TFTs exhibit high electron mobility even if those TFTs are fabricated under room-temperature 1. Many researchers have presented transparent conducting oxides (TCO)2 which transforms from a semiconductor to a conductor such as Indium zinc oxide (IZO), or Indium tin oxide (ITO). Increasing the number of oxygen vacancies which can control the carrier concentrations inside TCO will induce the conductive behavior. UV/ ozone treatment is a candidate method to improve the TFT performance by readjusting oxide material’s chemical structure and increase the number of oxygen vacancies by breaking the metal oxide bonds inside the oxide material3.
In this study, we fabricate self-aligned TFTs through an all-solution process method by using IZO with In:Zn = 77:23 by an atomic ratio as a semiconductor and electrode material. A self-aligned TFT structure is important to reduce the parasitic capacitance and contact resistance with the metal electrode. Here, we will show how UV/ozone treatment at different conditions can be used to increase the number of oxygen vacancies in IZO and transform it into an electrode. The 50-nm-thick IZO layer is deposited by spin coating on Si with thermal SiO2. Gate insulator used is a solution hybrid polymer4 with a thickness of around 150 nm. To make source/drain and gate electrodes we deposit IZO layer again on top and then utilize the UV treatment to irradiate specific areas of the IZO film reducing the sheet resistance (Rs) of the affected area. The Scanning Transmission Electron Microscopy (STEM) images clearly show no contact defect between the interface of the hybrid polymer and IZO layer which were both stacked by spin coating. We observed that IZO layer after UV-ozone treatment at 300°C for 30 min has a lower sheet resistance of 135.61 Ω/square than as-fabricated IZO layer which showed very high resistance. The transmission line model (TLM) method also confirmed that the contact resistance of IZO TFT after 300°C annealing in atmospheric ambient is 1x104 Ω — lower than as-fabricated IZO TFT which shows 2.5x107 Ω.
The electrical properties are evaluated by analyzing the TFT transfer characteristics. Furthermore, the mechanism will be elucidated by performing Secondary Ion Mass Spectrometry (SIMS) for diffusion study, and X-ray Photoelectron Spectroscopy (XPS) for chemical structural observations and comparing the oxygen vacancy concentrations between IZO before and after UV-ozone treatment.
Acknowledgement
We thank our research collaborator from Nissan Chemical Industries, LTD for providing us their IZO solution materials.
1. T. Kamiya, et al., Sci. Technol. Adv. Mater. 11, 044305, 2010.
2. H. Liu, et al., Superlattices and Microstructures 48, 458-484, 2010.
3. Y. J. Tak, et al., Sci. Rep., 6, 21869, 2016.
4. C. Kulchaisit, et al., J. Disp. Tech. 12, No. 3, 2016.
8:00 PM - EM10.05.04
Low-Temperature Solution-Processed Sol-Gel K-Rich KNN Thin Films for Flexible Electronics
Rajinder Deol 1 , Meenal Mehra 1 2 , Bhaskar Mitra 1 , Madhusudan Singh 1
1 Electrical Engineering, Indian Institute of Technology Delhi, New Delhi India, 2 , Momentive Performance Materials (India) Pvt. Ltd., Bengaluru India
Show AbstractSputtered lead-free piezoelectric materials like potassium sodium niobate (K1-xNaxNbO3 or KNN) have received significant technological interest in recent years in light of several reports of piezoelectric constants comparable to lead zirconium titanate (PZT). Potential applications include self-powered sensors, actuators, and low acoustic impedance transducers. For large area printed applications, it is vital to develop low-temperature solution processed deposition methods. In this work, sol-gel synthesis of K-rich (70:30) KNN was carried out under an argon atmosphere, using acetate precursors, followed by precipitation of white KNN powder upon careful drying. Powder X-ray diffraction (XRD) scans of the product with a Cu Kα source after calcination revealed a dominant (110) peak, accompanied by smaller (100) and (010) peaks, in agreement with published standard KNN data. The composition of K-rich phase was confirmed using energy dispersive X-ray spectroscopy (EDX). To produce thin films, the sol was spin coated on a surface-treated Au-coated Si substrate, followed by slow annealing to obtain low surface roughness films (RMS roughness < ~10 nm) of thickness ~200 nm after solvent removal. Atomic force microscopy (AFM) scans revealed an unremarkable amorphous film. However, deposition of the sol on Au-coated backside Si under similar processing conditions revealed limited polycrystalline film formation observed using optical profilometry. Thin film XRD measurements of the deposited film reveal orthorhombic phase growth of KNN, though the sol-sourced film was more amorphous than the calcined KNN product. Very preliminary polarization force microscopy (PFM) scans using a hard conductive tip are used to estimate a piezoelectric constant (d33) ~ 2.7 pC/N, consistent with the general expectation of lower piezoelectric constants for thin sol-gel films. The highest processing temperature used at any step during the deposition process was 90°C, consistent with the applications involving flexible polyimide substrates. This low-temperature thin-film growth suggests a potential route towards integration of large area piezoelectric generators for environmentally-friendly autonomous flexible sensor applications, with better control of phase and composition during the solution-phase deposition of KNN.
8:00 PM - EM10.05.05
Combustion Synthesis of CuCrO2 and Cu:CrOx Films at 180°C
Jian Wang 1 2 , Trey Daunis 1 , Lanxia Cheng 1 , Bo Zhang 1 , Jiyoung Kim 1 , Julia Hsu 1
1 Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas, United States, 2 Chemistry, University of Washington at Seattle, Seattle, Washington, United States
Show AbstractP-type transparent conducting oxides (TCOs) with good performance are critical in a variety of applications that requires transparency, conductivity, and circuit complexity. Low-temperature solution processing enables low-cost, large-area manufacturing methods on flexible substrates. Here we report solution synthesis of two p-type TCO thin films: copper chromium oxide (CuCrO2) and copper doped chromium oxide (Cu:CrOx). Using combustion chemistry, both films are made at 180°C, much lower than typically reported ~ 400 °C range. While adopting the same precursor preparation and annealing temperature, annealing under solvent vapor vs. open air dictates the resulting film phase, hence the optoelectronic properties. The effect of annealing environment on the reaction mechanism will be discussed. We further characterize the electronic, optical, and transport properties of the two materials, and compare the differences. Their applications in optoelectronic devices are successfully demonstrated in transparent p-n junction diodes and as hole transport layers in organic photovoltaic devices.
8:00 PM - EM10.05.06
Ferroelectric Hf0.5Zr0.5O2 Thin Films Fabricated Using Sol-Gel Method
Junyoung Lee 1 , Gopinathan Anoop 1 , Owoong Kwon 2 , Changjae Roh 1 , Yunseok Kim 2 , Jongseok Lee 1 , Ji Young Jo 1
1 , GIST, Gwangju, SE, Korea (the Republic of), 2 , Sungkyunkwan University Advanced Institute of NanoTechnology, Suwon Korea (the Republic of)
Show AbstractNon-centrosymmetric Hf0.5Zr0.5O2 thin film is a promising candidate in the Si-friendly ferroelectric memory devices. The Hf0.5Zr0.5O2 thin films grown on TiN layer can possess non-centrosymmetric orthorhombic phase in association with ferroelectricity, which is different from non-ferroelectric monoclinic phase of undoped HfO2 thin film. The most common method to fabricate the Hf0.5Zr0.5O2 films is atomic layer deposition (ALD); however, the ALD process requires high cost for high vacuum and deposition temperature. In this study, we report the growth of ferroelectric Hf0.5Zr0.5O2 films with non-centrosymmetric orthorhombic phase using a cost-effective and facile sol-gel technique.
Hafnium isopropoxide isopropanol (C15H36O5Hf) and zirconium dinitrate oxide hydrate (N2O7Zr xH2O) were dissolved in 2-Methoxyethanol at 75°C for 12 hours. Prior to the deposition of Hf0.5Zr0.5O thin films, TiN film was deposited on (100)-oriented n++ Si substrate using DC sputtering technique. The solution was spin-casted on top of TiN/Si substrate at a spin speed of 3000 rpm for 30 sec. Sequently, films were baked at 150°C for 10 min using a hot plate and then were annealed at a temperature in a range from 500 to 900°C for 1 hour in N2 ambient. Pt top electrodes with a thickness of 30 nm were deposited using an electron beam evaporator to form capacitor structures. The crystal structure were characterized using grazing incident X-ray diffraction technique. Second harmonic generation (SHG) was used to prove the non-centrosymmetry of fabricated films. The ferroelectricity of the films was confirmed using a piezoresponse force microscopy (PFM). We observed the most strong orthorhombic phase and largest piezoresponse for the sample annealed at 600°C.
8:00 PM - EM10.05.07
Cerium Oxides Film Preparation at Ambient Temperature and Atmosphere
Yuta Kubota 1 , Tetsuo Kishi 1 , Tetsuji Yano 1 , Nobuhiro Matsushita 1
1 , Tokyo Institute of Technology, Tokyo Japan
Show AbstractDeposition process of functional oxide films such as CeO2, ZnO and ITO are important research topics since they are applicable for various devices. In general, these films are prepared by spray-pyrolysis, sputtering, chemical vapor deposition and so on, which require high process temperature and/or the evacuation system. In this research, crystalliezed CeO2 film was prepared at 60oC by liquid phase deposition with delicate pH control. This novel process which provides low environmental load and low cost film preparation is named as Basic Gas assisted in Liquid Deposition (BGLD) in this study.
BGLD process is carried out at liquid-solid interface by keeping pH almost constant in weak acid range. The appropriate pH value for the preparation of CeO2 was from 4.6 to 5.2. Two containers which contain Ce salts aq. solution and HMT (hexamethylenetetramine) aq. solution, respectively, were put into a sealed vessel keeping pH in this range. NH3(g) vaporized from the HMT solution at quite a slow speed reached at the Ce salts solution. Plasma treated Ni and polyether sulfone (PES) substrates were placed at the bottom of the Ce salts solution. The temperature of sealed vessel was 60oC.
The surfaces of substrates and the container surface of Ce salts solution were changed into white after 3 days preparation. According to XRD patterns and SEM images, these surfaces were covered with crystallized CeO2 films. The formed films exhibited strong adhesion to the substrates and did not be exfoliated by ultrasonication. The film thickness on the PES substrate was about 130 nm, and the films exhibit the same optical absorption edge as CeO2 film which was prepared at 300oC by spin-coating. When the pH value was not in appropriate condition, amorphous films or crystallized precipitation were formed.
Formation Gibbs energy of CeO2 from Ce3+, H2O and dissolved O2 is negative at 60oC. However, CeO2 is not formed due to very low reaction rate. Therefore, the addition of small amount of NH3(g) to the Ce salts solution was attempted to increase the reaction rate. The increase of OH- concentration leads to generating reaction of H+ with CeO2 formation. When the amount of NH3 gas dissolved into the Ce salts solution was too much, CeO2 precipitates were formed.
Crystallized CeO2 film was formed on Ni and PES substrate at 60oC by a novel liquid phase deposition, Basic Gas assisted in Liquid Deposition process. This process does not need high process temperature and the evacuation system. The oxide films can be formed on liquid-solid interface. The oxide films can be formed on 3D substrates.
8:00 PM - EM10.05.08
High-Surface Mg3N2—Photoluminescence and CO2 Sorption
Viktor Rein 1 , Claus Feldmann 1
1 Institute of Inorganic Chemistry, Karlsruhe Institute of Technology, Karlsruhe, Baden-Württemberg, Germany
Show AbstractAlthough magnesium nitride (Mg3N2) is known for a long time, its electronic and optical properties are still not fully understood. Especially, the value of the band gap resulting from computations (1.10 - 2.25 eV)[1, 2] or optical measurements (2.8 eV)[3] differs drastically. Despite of the predominantly ionic bonding situation, Mg3N2 can be considered as a semi-conductor with a direct band gap. So far, Mg3N2 is mainly used as a catalyst for the synthesis of various nitrides, e. g., Si3N4 and c-BN.[4] Currently, it is especially discussed as an alternative to AlN and GaxAlyN for optoelectronics since they exhibit unfavourable indirect band gaps.[5] The synthesis of Mg3N2 is usually performed by direct reaction of magnesium and nitrogen at high temperature. Reports about nanostructured Mg3N2 are rather rare, especially, due to the high sensitivity of both product and intermediates to moisture.
Here, we report on the synthesis of high-surface Mg3N2 by the ammonolysis of an organomagnesium precursor within a liquid crystalline template (LCT) using liquid ammonia as the polar phase and subsequent annealing.[6, 7] The composition and phase purity of the formed yellow compound were confirmed by X-ray powder diffraction and electron microscopy (SEM, STEM, HRTEM, EDX, EELS). UV-VIS spectroscopy results in a band gap of 2.87 eV, and hence, confirms the value reported by Reckeweg et al.[3]
Powder samples show high specific surface areas (176 m2 g-1) as well as a high porosity (0.41 cm3 g-1). Moreover, we could prove via gravimetric sorption analysis that the basic nitride leads to good sorption capability of acidic carbon dioxide (CO2). We also studied the selectivity compared to nitrogen with regard to a potential application in selective gas separation.
Furthermore, the as-prepared Mg3N2 shows red photoluminescence under excitation with blue light, and thus, in the range of the measured band gap. The quantum yield was determined to 10 %. Until now, no report of red emitting Mg3N2 is found in the literature. In order to modulate the emission wavelength as well as to increase the quantum yield, we also studied the effect of selective doping.
[1] C. M. Fang, R. A. d. Groot, R. J. Bruls, H. T. Hintzen, G. d. With, J. Phys.: Condens. Matter 1999, 11, 4833.
[2] M. M. Armenta, A. Reyes-Serrato, M. A. Borja, Phys. Rev. B 2000, 62, 4890.
[3] O. Reckeweg, C. Lind, A. Simon, F. J. DiSalvo, Z. Naturforsch. 2003, 58b, 159–162.
[4] D. H. Gregory, Coord. Chem. Rev. 2001, 215, 301.
[5] D.-W. Kim, T.-H. Kim, H.-W. Park, D.-W. Park, Appl. Surf. Sci. 2011, 257, 5375.
[6] F. Gyger, P. Bockstaller, D. Gerthsen, C. Feldmann, Chem. Mater. 2016, 28, 7816.
[7] V. Rein, C. Feldmann, in preparation 2017.
8:00 PM - EM10.05.09
Annealing Temperature Dependent Analytical Studies on Oxygen Plasma Treated Solution-Processed Nickel Oxide—New Insights into the Correlation of Chemical and Electronic Properties
Florian Ullrich 1 2 , Sabina Hillebrandt 1 3 , Sebastian Hietzschold 1 4 , Valentina Rohnacher 1 3 , Wolfram Jaegermann 2 1 , Annemarie Pucci 3 1 , Wolfgang Kowalsky 4 1 3 , Robert Lovrincic 1 4 , Sebastian Beck 1 3 , Eric Mankel 1 2
1 , InnovationLab GmbH, Heidelberg Germany, 2 , TU Darmstadt, Darmstadt Germany, 3 , Universtität Heidelberg, Heidelberg Germany, 4 , TU Braunschweig, Braunschweig Germany
Show Abstract
Solution-processed nickel oxide (sNiO) is known to efficiently improve performance of opto-electronic devices when used as charge selective interlayer. Its benefits further can efficiently be enhanced by a simple oxygen plasma (OP) treatment step. To shed light on the processes and their effects taking place during this treatment we study the structural, chemical and electrical properties of sNiO after different annealing temperature dependent stages of precursor conversion and the respective effects of OP treatment. For this purpose we use atomic force microscopy, angle-resolved infrared transmission spectroscopy and (angle-resolved) X-ray photoelectron spectroscopy. We find that the extent of transformation is reflected in an increasing degree of order and a decreasing ratio between the predominant nickel hydroxide species α-Ni(OH)2 and stoichiometric NiO. Furthermore, we show that a more complete conversion of the precursors results in a lower work function. The changes in the IR spectra upon OP treatment are attributed to a conversion of β-Ni(OH)2 into β-NiOOH. Since the work function after OP is the same for all samples (5.5 – 5.6 eV) we propose that for all annealing temperatures OP treatment leads to chemically similar β-NiOOH-like phases in the first atomic layers. This is further confirmed by I-V measurements, showing similar conductivities after OP treatment.
8:00 PM - EM10.05.10
Reduced Water Vapor Transmission Rates (WVTRs) of Low Temperature, Solution Processed (Sol-Gel-Derived) TiOx Passivation Layers for Flexible Electronic Applications
Yonghwa Baek 1 , Chan Eon Park 1
1 , Pohang University of Science and Technology, Pohang Korea (the Republic of)
Show AbstractSol-gel-derived, crack-free, and condensed TiOx thin films with improved barrier properties were successfully fabricated on polymeric substrates with a simple two-step heat treatment at low temperatures. To evaluate the film properties of the TiOx thin films, FT-IR peaks, refractive index, optical microscopy (OM) and atomic force microscopy (AFM) images were investigated. As a result, the number of cracks in the TiOx films decreased in size as the thickness of the TiOx films on the PEN substrates was reduced. Almost no cracks were evident in the 43 nm thick TiOx thin films on PEN substrates even after 110 °C heat treatment. However, 43 nm thick TiOx thin films were expected to be too thin for use as efficient passivation layers and therefore, we tried to achieve thicker crack-free TiOx thin films. Thicker crack-free films (86 nm and 129 nm) of TiOx were obtained on PEN substrates through the fabrication of 43 nm thick TiOx thin film multilayers by repeating the spin-coating and the two-step annealing processes.
Finally, to assess the barrier properties of the TiOx thin films, Ca corrosion tests were conducted and their water vapor transmission rates (WVTRs) were measured. We found that the two-step heat treatment (at 45 °C for 90 min and 110 °C for 60 min) produces a close-packed TiOx structure that substantially reduces the WVTRs of the coated polymeric substrates. The WVTRs of 86 nm thick TiOx thin films on polyethylene naphthalate (PEN) substrates at a relative humidity (RH) of 90% were found to be 0.133 g m−2 day−1 at 38 °C and 0.0387 g m−2 day−1 at 25 °C. For reliable operation of organic transistors, required water vapor transmittance rates (WVTRs) are known to be typically in the range of 10−2 g m−2 day−1 ∼ 10−3 g m−2 day−1. In addition, the WVTR value of the TiOx thin films on PEN substrates were stable with respect to bending: it was found to increase by only ∼13% after 100 repetitions of bending with a 20 mm radius.
8:00 PM - EM10.05.11
Back-Channel Engineering of Ultrathin Printed Indium Oxide Transistors for Carbon Dioxide Sensing
Yasuhiro Kobayashi 1 , William Scheideler 1 , Vivek Subramanian 1
1 Electrical Engineering and Computer Sciences, University of California, Berkeley, California, United States
Show AbstractMetal oxide TFTs have high carrier mobility and high back-channel sensitivity suitable for low power gas sensor applications. The sensing of carbon dioxide gas (CO2) is important for indoor air quality monitoring because CO2 has a direct and negative impact on human cognition and decision-making performance at the thousands of ppm level. Conventional nondispersive infrared sensors and chemiresistors are not widely used for these applications due to their high cost and high power consumption, respectively. Metal oxide TFTs can be candidates for low cost and low power consumption sensors if they can be fabricated at lower cost by solution processing and can detect CO2 at room temperature. This work addresses these challenges by fabricating TFTs with inkjet printing and by depositing amines as CO2 sensitizing layers.
TFTs with printed ITO source/drain electrodes and indium oxide (InOx) semiconductors were prepared from ITO nanoparticle dispersions and 2-methoxyethanol solutions of indium nitrate, respectively, at ≤ 250 °C on SiO2/Si wafers. Amine sensitizing layers were thermally vapor deposited, inkjet printed or spin coated on the back-channel of InOx TFTs. The sensitivity of the TFTs’ electrical properties to CO2 was investigated as a function of the amine composition and thickness. TFTs coated with thin layers (< 5 nm) of primary or secondary amines exhibited increasing drain current with exposure to CO2 and recovery upon a purging with N2. These TFTs were sensitive to CO2 concentrations from 300 ppm to 3000 ppm in N2, showing monotonic increases in current with increasing CO2 concentration. In contrast, TFTs without amines show no significant response to CO2 concentrations up to 3000 ppm. This work represents the first demonstration of printed-TFT-based and metal-oxide-TFT-based CO2 sensors.
8:00 PM - EM10.05.12
Visible Light Reactive N-Contained ZnO Nanorod Arrays Synthesized by Hydrothermal Method
Ryosuke Kobayashi 1 , Tetsuo Kishi 1 , Tetsuji Yano 1 , Nobuhiro Matsushita 1
1 , Tokyo Institute of Technology, Meguro-ku Japan
Show AbstractZnO has attracted a lot of interests because of its many superior properties. Introduction of N in ZnO reduces the absorption energy and thus it can absorb visible light. N-contained ZnO nanorod arrays (N:ZnO NRAs) are expected to be applied for visible light reactive photoelectrode because of their many advantages such as high diffusion length of the charge carriers and high surface to volume ratio. Typical fabrication processes of N:ZnO NRAs are gas-phase processes, but these processes usually require high vacuum and high temperature. Compared with these methods, solution processes are easy ways to fabricate ZnO NRAs and are attractive for their cost-efficiency and good potential in scale-up. In general, both solution process and following post-growth doping are adopted to fabricate N:ZnO NRAs. Among the conventional post-growth doping methods, NH3 heat treatment is one of the most typical ways to incorporate N into the crystals keeping their original morphology. However, NH3 is toxic gas and the N dopant distribution within the crystals cannot be effectively controlled in this method. In this study, the N:ZnO NRAs were fabricated by cost-effective hydrothermal synthesis without using post-doping method, and their responses to visible light were evaluated.
Experimental processes were as follows: 10 mL of aqueous 2.5 M NaOH was added dropwise to 15 mL of aqueous 0.5 M Zn(NO3)2. The resulting hydroxide slurry was centrifuged and the supernatant was removed. Rinsing and separation were carried out four times to remove Na+ and NO3-. The resulting precipitate was dissolved in 50 mL of aqueous 6.6 M NH3 to form a zinc-ammine complex solution. The cleaned FTO glass was spin coated by zinc-ammine complex solution and annealed at 150°C for 5 min. This cycle was repeated for 10 times to obtain ZnO seeded FTO glass. The obtained ZnO seeded FTO glass was put into the growth solution, which was formed by diluting the zinc-ammine complex solution with distilled water in three times, and then maintained at 100°C for various reaction time. After the hydrothermal reaction, the sample was taken out immediately and rinsed with distilled water. The samples were annealed in some temperature.
The N:ZnO NRAs had strong c-axis orientation and grew vertically to the substrate. The length and diameter of the NRAs could be controlled by varying the hydrothermal reaction time. Nitrogen-related modes were observed in Raman spectra after appropriate annealing, thus it was confirmed that nitrogen successfully incorporated within ZnO lattice. It was showed that the absorption edge shifted toward the visible region compared with the literature value of ZnO (~380 nm). The N:ZnO NRAs also showed visible light (> 422 nm) driven photocurrent while there was almost no visible light driven photocurrent in pristine ZnO NRAs. These results suggest this cost-effective fabrication method has many potentials for application in solar water splitting.
8:00 PM - EM10.05.13
Solution Combustion Synthesis—Applications in Oxide Electronics
Rita Branquinho 1 , Ana Santa 1 , Emanuel Carlos 1 , Daniela Salgueiro 1 , Pedro Barquinha 1 , Rodrigo Martins 1 , Elvira Fortunato 1
1 Materials Science Department (DCM), CENIMAT/I3N, FCT-NOVA Faculdade de Ciências e Tecnologia (FCT) da Universidade NOVA de Lisboa and CEMOP/UNINOVA, Caparica Portugal
Show AbstractOxide based electronics have been well established as an alternative to silicon technology, however typical processing requires complex high vacuum equipment which is a major drawback, especially when targeting low cost applications.
The possibility to deposit the materials by low cost techniques such as inkjet printing has drawn tremendous interest in solution processible materials for electronic applications, however high processing temperatures still required. To overcome this issue solution combustion synthesis has been recently pursued. Taking advantage of the exothermic nature of the reaction as a source of energy for localized heating, the precursor solutions can be converted into oxides at lower process temperatures. Theoretically this can be applied to any metal ions to produce the desired oxide, opening unlimited possibilities to materials’ composition and combinations. Solution combustion synthesis has been applied for the production of semiconductor and transparent conductor oxides (TCO) thin films based on ZnO, In2O3, SnO2 and combinations of these oxides, and also for high κ dielectrics (Al2O3 and HfO2). All of which are required for numerous electronic devices and applications such as fully oxide based TFTs. The properties of produced thin films are highly dependent on the precursor solution characteristics; hence the influence of several processing parameters; organic fuel, solvent and annealing temperature were studied. Although precursor solution degradation/oxide formation mechanisms are not yet fully understood, especially for thin films, we demonstrate that high performance devices are obtained with combustion solution based metal oxide thin films. The results clearly show that solution combustion synthesis is becoming one of the most promising methods for low temperature flexible electronics.
8:00 PM - EM10.05.14
Boosting the Electrical Performances of Solution-Based High-κ Multilayer Dielectrics at Low Temperature and Their Application in Electronic Structures
Emanuel Carlos 1 , Rita Branquinho 1 , Asal Kiazadeh 1 , Jorge Martins 1 , Pedro Barquinha 1 , Elvira Fortunato 1 , Rodrigo Martins 1
1 Materials Science Department, CENIMAT/I3N, Faculdade de Ciencias e Tecnologia (FCT), Universidade NOVA de Lisboa (UNL) and CEMOP/UNINOVA, Caparica Portugal
Show AbstractIn the last decade solution-based dielectric oxides have been widely studied in electronic applications enabling the use of low cost processing technologies and devices improvement. The most promising are the high-κ dielectrics, like aluminum (AlOx) and hafnium oxide (HfOx), that allow an easier trap filing in the semiconductor and the use of low operation voltage. However, in the case of HfOx a high temperature is usually needed to induce a uniform and condensed film, which limits its applications in flexible electronics. This paper describes how to obtain HfOx dielectric thin films and the effect of their implementation in multilayer dielectrics (MLD) at low temperatures (150 °C) to apply in thin film transistors (TFTs) using the alliance between solution combustion synthesis (SCS) and ultraviolet (UV) treatment.
The single layers and multilayers exhibited the elimination of all the residual organics, a small surface roughness (< 1.2 nm) and a high breakdown voltage (> 2.7 MV.cm-1). The resulting MLD/GIZO TFTs presented a high performance at a low operation voltage (< 3 V), with high saturation mobility (43.9 ± 1.1 cm2.V-1.s-1), a small subthreshold slope (0.066 ± 0.010 V.dec-1), current ratio of 106, and a good stability after 2 months. To our knowledge, the results achieved surpass the state-of-the-art. Finally, we demonstrated a low-voltage diode-connected inverter using MLD/GIZO TFTs working at a switching speed of 100 Hz with a maximum gain of 1 at 2 V.
8:00 PM - EM10.05.16
Effect of Film Thickness on Solution-Processed Amorphous Indium-Gallium-Zinc Oxide Thin-Film Transistors Formed by Hexaaqua Metal Complexes
Chanyeol Choi 1 , Yongmin Baek 2 , Yunjo Kim 1 , You Seung Rim 3
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 , Yonsei University, Seoul Korea (the Republic of), 3 , Sejong University, Seoul Korea (the Republic of)
Show AbstractSolution-processed metal oxide thin film transistor (TFT) have faced the challenge of realization of high performance solution-based TFT without high temperature annealing process, although it is advantageous to straightforward device fabrication without a high vacuum-demanding system. We investigated electrical performance of solution-processed and low temperature annealed metal oxide semiconductor devices made out of hexaaqua metal complexes. The thickness of oxide film Indium-Gallium-Zinc-Oxide (IGZO) ranged from 4 nm to 16 nm. It is noteworthy that 4 nm thick TFT showed high performance with 7.73±0.44 cm2 V-1s-1 (Field effect mobility), 108 (on/off ratio) as a notch above the rest. The device performance, such as carrier density and threshold voltage, degraded with increasing film thickness, which contradicts the tendency in vacuum-processed metal oxide TFT. We further performed bias stress stability test by positive gate-bias stress (PBS) and negative gate-bias test (NBS). Interestingly, 4 nm thick TFT achieved excellent stability under both PBS and NBS. This phenomenon is attributed to both low film density induced by solution-based process and trap charge caused by rough surface, which are confirmed by X-ray reflectivity spectroscopy (XRR) and atomic force microscopy (AFM).
8:00 PM - EM10.05.17
Recovering of Resistive Switching Characteristics in Vanadium Oxides Based Multilayer Memristor Structure
Xin Zhou 1 , Deen Gu 1 , Rui Liu 1 , Haoxin Qin 1 , Shiyang Xu 1 , Yadong Jiang 1
1 , University of Electronic Science and Technology of China, Chengdu, Sichuan, China
Show AbstractResistance switching memristors have attracted wide attentions as potential non-volatile semiconductor memory devices. However, the declining of switching properties with switch times is an annoying issue. Here we investigated the resistive switching characteristics of ITO/VOx/V2O5-y multilayers. The VOx layer was deposited by a DC reactive magnetron sputtering process on ITO substrate. Then, V2O5-y was formed by a rapid thermal annealing process at 400 oC in air atmosphere for 10 min. Using Ag tip as top electrode, the I-V curve of ITO/VOx/V2O5-y multilayers was recorded by a 4200 semiconductor analyzer. It shows a typical resistive switch feature with an on/off ratio about 35 after an electrical forming process with the forming voltage of -2.0 V. The set/reset voltages are -1.4 V and 0.5 V, respectively. Unfortunately, the resistive switching feature gradually declines within about 1000 scanning cycles, even disappears although the scanning voltages are much larger than the set/reset voltages. But the switching feature can be recovered by applying a negative voltage (-6 V). The recovered memristor switching feature can be clearly observed even without a further forming process. Differently, the on/off ratio of recovered memristor (about 10) is smaller than the one of as-prepared memristor. The declining of the switching feature for ITO/VOx/V2O5-y multilayers memristor could originate from gradually-enhanced conducting filaments during scanning cycles. As the conducting filaments are too strong to be interrupted by a resetting voltage, a low-resistance state is kept. Once a much higher reverse voltage than the resetting voltage is applied, the conducting filaments are interrupted, the sample recovers to a high-resistance state. Thus a memristor switching feature reoccurs. The recovering process could not move the conducting filaments thoroughly back to the initial high-resistance state. Therefore, the on/off ratio of recovered memristor is smaller than as-prepared memristor.
8:00 PM - EM10.05.18
Sonochemically Synthesized ZnO Nanostructure-Based L-Lactate Enzymatic Sensors on Flexible Substrates
Fahmida Alam 1 , Raju Sinha 1 , Yougeswaran Umasankar 1 , Ahmed Jalal 1 , Shekhar Bhansali 1 , Nezih Pala 1
1 Electrical and Computer Engineering, Florida International University, Miami, Florida, United States
Show AbstractWe report on both highly sensitive and flexible L-lactate enzymatic sensors. The demonstrated biosensors are fabricated based on two-dimensional (2D) zinc oxide (ZnO) nanoflakes (NFs), which were synthesized on flexible Au-coated polyethylene terephthalate (PET) substrate using simple one step sonochemical approach for noninvasive lactate monitoring in human perspiration. Highly sensitive detection of Lactate using cyclic voltammetry (CV) is achieved by immobilizing lactate oxidase (LOx) on the as-synthesized sensing electrodes of ZnO-NFs accordingly.
ZnO nanostructures show significant potential for use in biosensors because of their diverse range of morphologies that possess large specific surface area, high isoelectric points which promote the electrostatic adsorption of enzymes without any intermediate linker layer, biocompatibility which provides a favorable micro-environment for retaining enzyme activity. In addition, high crystallinity of ZnO nanostructures (NSs) provide direct electron conduction tunnels between the enzyme active sites and electrode surface, without requiring a mediator. Considering their promising properties and potential applications, many techniques have been developed to synthesize various ZnO nanostructures. In comparison to the more conventional approaches such as hydrothermal method, sonochemical synthesis method is not only significantly faster, inexpensive and performed at ambient conditions but also highly stable and reproducible with the advantages of more uniform size distribution, faster reaction time and a higher surface area, which are essential to design sensing platform with improved performance. Compared to bulk materials, the 2D ZnO NFs provide unique sensing advantages with polarized (0001) plane orientation and high surface charge density, which could enhance the surface functionalization and thus improve sensing performance.
Taking advantage of these unique properties of ZnO NSs, we immobilized LOx on the synthesized ZnO NFs. The CV measurements were taken in the potential range of -0.1V to -0.5V at a scan rate of 20mVs-1 and the sensitivity of the sensor was found to be 2.23μA/M /cm2. PET/Au/ZnO NFs sensor demonstrated detection of lactate in the range of 10pM-10µM for the electrode area of 0.5×0.5 cm2. PET/Au/ZnO NFs based lactate sensor (without linker) shows 4 times better response than conventional gold electrode with linker. High isoelectric point allows a direct, stable pathway for rapid electron transport without any mediator when an analyte is immobilized on NFs and improves electron transfer rate. We also investigated the repeatability, selectivity and lifetime of the demonstrated biosensors.
8:00 PM - EM10.05.19
Study on the Effect of Solvents on Fabricating ZnO Thin Films by Solution-Based Mist Chemical Vapor Deposition
Misaki Nishi 1 , Li Liu 1 , Phimolphan Rutthongjan 1 , Shota Sato 1 , Masahito Sakamoto 1 , Yusuke Kobayashi 1 , Mariko Ueda 1 , Ellawala Pradeep 1 , Giang Dang 1 , Toshiyuki Kawaharamura 1
1 , Kochi University of Technology, Kami Japan
Show AbstractNon-vacuum deposition technology "mist CVD" was developed about 10 years ago. However, the growth reaction mechanism in mist CVD has not been established thus we must elucidate these mechanisms. This study investigated the relationship between changes in growth mechanism and crystal quality due to different precursor solutions used for fabricating ZnO thin film by mist CVD. To this end, we prepared three types of precursor solutions i.e., mixture of methanol and ethylene diamine (C1); mixture of methanol, pure water, and ethylene diamine (C2); and mixture of methanol, water, and ammonia solution (C3). Different growth temperatures in the range of 200-400 °C were investigated. Crystal structure, optical and electric characteristics of the fabricated ZnO thin films were evaluated with the purpose to understand the corresponding effects in a qualitative and quantitative manner. In the case of C1 which did not included water as a constituent of the precursor solution, the deposition rate of ZnO increases as the temperature rises, indicating that reaction is under kinetic control at these conditions. This indicates excessive amount of new precursor materials is supplied over the entire substrate. On the other hand, in the cases of C2 and C3 which did not include water as a constituent of the in the precursor solutions, the deposition rate was constant even though the temperature was changed. Therefore, it is clear that as the growth rate is under mass transfer control at these conditions. This indicates there is enough time for precursor material to achieve towards the substrate and to contribute for the crystal growth. Moreover, sharp XRD peak of the ZnO (002) plane can be seen under C1, when the film growth temperature was 400 °C . In contrast, the sharp peak was seen under C2 and C3 at low temperature (300 °C ).
Therefore, it is possible to grow ZnO thin films with high crystallinity under the kinetic control conditions using C1 at high temperature. On the other hand, ZnO thin film with high crystallinity can be obtained under mass transfer controlled conditions using C2 and C3 at low temperature. Therefore, it can be considered that high quality thin films can be grown up at a critical value of temperature which changes the reaction from kinetic control conditions to mass transfer control conditions. Impurities or defects incorporated in the film were measured by photoluminescence. It was confirmed that the condition C2 which contain ethylene diamine as a constituent in the precursor solution incorporated impurities or defects in the film in comparison to that of C3. Thus, the growth of high quality ZnO thin by mist CVD films using different precursor solutions and a study of the corresponding reaction mechanisms are discussed in this paper.
I would like to explain these results in more detail on that day and conduct interactive discussions in the conference.
8:00 PM - EM10.05.20
ITO Optical Fiber Sensor Behavior for Intermediate Temperature Applications
Youngseok Jee 1 2 , Jacob Poole 1 , Thomas Kalapos 1 2 , Shiwoo Lee 1 2 , Harry Abernathy 1 2 , Gregory Hackett 1 , Paul Ohodnicki 1
1 , National Energy Technology Laboratory, Pittsburgh, Pennsylvania, United States, 2 , AECOM, Pittsburgh, Pennsylvania, United States
Show AbstractHighly electronic-conductive indium tin oxide (ITO) coated silica optical fiber sensor was prepared by sol-gel method to investigate its sensor responsive characteristics targeting in-situ monitoring for intermediate temperature applications ranging from 250 to 450°C. The hydrogen introduction (5-100%) experiment at various operational temperatures was conducted and transmission decrease related to surface plasmon resonance due to the free carrier increase was monitored in near-infrared (NIR) wavelength range. The transmission instability which showed wavelength shift and peak broadening has been observed at higher temperature (> 400°C). In addition to hydrogen, other chemical exposure tests also have been conducted (carbon dioxide, carbon monoxide and methane) at 350°C. Most of responses in reducing gases showed similar behavior in near-infrared and visible range with different intensity values (hydrogen > carbon monoxide > methane) where the sensor was non-responsive in carbon dioxide environment. Principal component analysis (PCA) was applied to identify the relationship between sensing mechanism and selective gas.
8:00 PM - EM10.05.21
MIS Capacitance Model of Solution-Processed Combined Gate-Dielectrics for Oxide Thin-Film Transistors
Woon-Seop Choi 1 , Hun Ho Kim 1
1 , Hoseo University, Asan Korea (the Republic of)
Show AbstractAmorphous oxide semiconductor thin film transistors (TFTs) have attracted much attention with distinguished features of high optical transparency, high mobility, good compatibility, and solution process ability compared to traditional a-Si TFT process. Solution-process fabricated TFTs are attracting increased interest due to the advantages of low cost and high throughput compared to conventional vacuum techniques. The solution-processed zinc tin oxide (ZTO) TFTs based on SiO2 gate dielectric that are easily inclined to make oxygen vacancies do not show good device performances. Also, the leakage current of SiO2 of nanometer scale increased dramatically owing to the tunneling effect. Thus, if a mixed system of ZrO2 and Al2O3 (ZAO) is used as the gate dielectric, electrical properties of TFTs will be improved because of the good interface state and oxygen vacancy suppression in the nearby ZTO system through aluminum and zirconium. There have been reports on double or stacked semiconductors, however, almost no report was found on mixed or stacked soluble gate dielectric system so far.
Solution-processed gate dielectrics were fabricated with the combined ZrO2 and Al2O3 (ZAO) in the
form of mixed and stacked types for oxide thin film transistors (TFTs). ZAO thin films prepared with
double coatings for solid gate dielectrics were characterized by analytical tools. For the first time, the
capacitance of the oxide semiconductor was extracted from the capacitance-voltage properties of the
zinc-tin oxide (ZTO) TFTs with the combined ZAO dielectrics by using the proposed metal-insulator semiconductor (MIS) structure model. The capacitance evolution of the semiconductor from the TFT model structure described well the threshold voltage shift observed in the ZTO TFT with the ZAO (1:2) gate dielectric. The electrical properties of the ZTO TFT with a ZAO (1:2) gate dielectric showed low voltage driving with a field effect mobility of 37.01 cm2/Vs, a threshold voltage of 2.00 V, an on-to-off current ratio of 1.46 × 105, and a subthreshold slope of 0.10 V/dec.
8:00 PM - EM10.05.22
Increase the Efficiency of Polymer Solar Cells with Keggin Type Polyoxometalates Interfacial Modifiers
Yasemin Topal 1 , Mahmut Kus 1 , Maria Maria Vasilopoulou 2
1 , Selcuk University Chemistry Department, Konya Turkey, 2 , Institute of Nanoscience and Nanotechnology (INN), Athens Greece
Show AbstractHere we demonstrate that water soluble Keggin type Polyoxometalates (POMs) can highly increase the efficiency, lifetime and photostability under constant illumination of solar cells application when used as interfacial modifiers between the titanium oxide (TiO2) electron transport/injecton layer and different photoactive blend. Optoelectronics devices based on this kind of interfacial modification of titanium oxide electron collection layers exhibit power conversion efficiency as high as 9.0% and exceptional photostability, which was obtained by incorporation of our POM modified TiO2 electron collection layers with the PTB7:PC71BM active layer and represents, to the authors knowledge, the highest value obtained in single-junction PSCs using TiO2 electron collection layers. The proposed method provides a new route for fabricating low-cost, environmentally friendly, high performing, extremely stable polymer solar cells.
8:00 PM - EM10.05.23
Solution Based Zinc Tin Oxide TFTs—The Dual Role of the Organic Solvent
Daniela Salgueiro 1 , Asal Kiazadeh 1 , Rita Branquinho 1 , Lidia Santos 1 , Pedro Barquinha 1 , Rodrigo Martins 1 , Elvira Fortunato 1
1 Materials Science Department (DCM), CENIMAT/I3N, FCT-NOVA Faculdade de Ciências e Tecnologia (FCT), da Universidade Nova de Lisboa and CEMOP/UNINOVA, Caparica, Portugal, Caparica Portugal
Show AbstractChemical solution deposition is a low cost, scalable and high performance technique to obtain metal oxide thin films. Recently, solution combustion synthesis has been introduced as a chemical route to reduce the processing temperature. This synthesis method takes advantage of the chemistry of the precursors as a source of energy for localized heating. According to the combustion chemistry some organic solvents can have a dual role in the reaction, acting both as solvent and fuel. In this work, we studied the role of 2-methoxyethanol in solution based synthesis of ZTO thin films and its influence on the performance of ZTO TFTs. The thermal behaviour of ZTO precursor solutions confirmed that 2-methoxyethanol acts simultaneously as a solvent and fuel, replacing the fuel function of urea. The electrical characterization of the solution based ZTO TFTs showed a slightly better performance and lower variability under positive gate bias stress when urea was not used as fuel, confirming that the excess fuel contributes negatively to the device operation and stability. Solution based ZTO TFTs demonstrated a low hysteresis (ΔV = −0.3 V) and a saturation mobility of 4–5 cm2 V−1 s−1.
8:00 PM - EM10.05.24
Influence of Spray-Pyrolysis Deposition Parameters on the Electrical Properties of Aluminum Zinc Oxides Thin Films
Denis Martins 1 , Giovani Gozzi 1 , Lucas Fugikawa Santos 2
1 , University of São Paulo State–UNESP, Rio Claro Brazil, 2 , University of São Paulo State–UNESP, São José do Rio Preto Brazil
Show AbstractTransparent metal oxides (TMOs) are semiconducting/conducting materials which have been regularly investigated in the past few years due to their interesting properties as the active semiconducting layer of electronic devices (such as thin-film transistors, TFTs) or as transparent conductive layer of optoelectronic devices as organic light-emitting diodes and solar cells. For most of these applications, TMOs thin-films are usually deposited by sophisticated techniques like RF sputtering or pulsed-laser deposition (PLD), which result in highly homogeneous and uniform films, with high optical transmittance and high electrical conductivity. However, the increasing demand for large scale production of devices with large areas has stimulated the pursuit for new, low-cost, alternative deposition techniques. In this sense, spray-pyrolysis (SP) is a simple, versatile, efficient and low-cost deposition method, which easily permits the upscaling to produce large-area devices. The electrical and optical properties of TMOs films produced by SP are strongly affected by processing parameters, such as deposition temperature, post-processing annealing and the metal oxide composition. In the current work, we evaluate the influence of the processing parameters on the electrical properties of aluminum zinc oxide (AZO) thin films produced by SP technique. Spray-deposited AZO thin-films were produced with Al:Zn molar ratios varying from 0% (pure ZnO) up to 30%, using aluminum acetate and zinc acetate as organic precursors and water as solvent. Thermogravimetric analysis (TGA) and infrared spectroscopy (FTIR-ATR) were used to monitor the metal-oxide formation from the organic precursors as a function of the temperature. The results show that a temperature of 400°C is necessary to completely degrade the organic phase and to obtain the desired inorganic metal-oxides films. The electrical properties of the TMOs were evaluated by d.c. current-voltage (I-V) analysis using planar thermally evaporated Al electrodes on top of the TMO layer, with different aspect ratios (1/18, 2/9, 5/13, 5/9 and 8/9). The lowest sheet resistance was obtained for AZO films at a molar Al concentration of 5%. We also observed that, after carrying out a post-annealing treatment (30 mbar, 150°C) the samples presented a decrease on the sheet resistance superior to 60%, in comparison to the samples before the treatment.
8:00 PM - EM10.05.25
Optimization of the Electrical Performance of Metal Oxide Thin-Film Transistors by Varying Spray Deposition Parameters
Guilherme Rodrigues de Lima 1 , João Paulo Braga 1 , Giovani Gozzi 1 , Lucas Fugikawa Santos 1 2
1 , Universidade Estadual Paulista - UNESP, IGC, Rio Claro Brazil, 2 , Universidade Estadual Paulista - UNESP, IBILCE, São José do Rio Preto Brazil
Show AbstractMetal oxides like zinc oxide are promising materials for active layer of thin-film transistors (TFTs) used in the drive circuit of next-generation large-area active matrix displays due to the high electronic mobility, high transmittance in the optical visible range and processability. Traditional deposition techniques employ RF sputtering or pulsed-laser deposition (PLD), which are relatively sophisticated techniques. The deposition of very thin (less than 50 nm thick) layers of ZnO using soluble organic precursors have been extensively investigated recently as an alternative to traditional deposition methods. Solution-based deposition processes include simple and affordable techniques like dip-coating, spin-coating, spray-pyrolysis and ink-jet printing. Spray-pyrolysis is particularly interesting due to the high film uniformity, low cost and high device performance. We carried out several experiments comparing the performance of ZnO based TFTs using zinc acetate as organic precursor to confirm that spray pyrolysis deposition results in much better devices in comparison to spin-coated TFTs. However, we observed that device performance can significantly vary with little modifications in the deposition parameters, even for the same active layer composition. Electrical parameters obtained from the characteristic TFT transfer curve as the electrical mobility and the on/off ratio varied more than 3 orders of magnitude, whereas the threshold voltage varied up to 20 V for the tested devices. Deposition parameters as the nozzle height during the deposition, solution concentration, nozzle air pressure, deposition time and surface treatment were varied until we obtained devices with optimum electrical performance. Optimized devices presented mobilities in the order of 1 cm2.V-1.s-1, on/off ratio about 107 and operation voltages close to 0V. A statistical analysis of a great number of devices manufactured using the same deposition parameters was carried out to assure the reproducibility of the deposition technique.
8:00 PM - EM10.05.26
Low-Temperature Deposition and Processing of High-k HfO2 Thin Films Using Supercritical Fluid Solution
Hiroshi Uchida 1 , Hiroaki Kawashima 1
1 , Sophia University, Tokyo Japan
Show AbstractNovel techniques for the deposition of inorganic thin films at lower processing temperature are strongly desired by manufacturers of electronic- devices because they enables the fabrication of high-performance integrated circuits on polymer or metal substrates with poor thermal stability. Recently, one unique process for the material synthesis at lower processing temperature have been reported, which utilized supercritical carbon dioxide (scCO2) fluid as a medium for related chemical reactions: In this process, the medium of supercritical fluid can promote the decomposition of metal-organic precursors (such as alkoxides and b-diketonates) and the extraction of the reaction byproducts to accelerate the formation of the metal oxide products. [1,2] So, based on this concept, we have proposed some self-produced apparatuses for thin-film deposition under the scCO2 medium (i.e., SuperCritical Fluid Deposition: SCFD), which allowed the deposition of metal-oxide films, such as TiO2, SiO2 and ZrO2, at reaction temperature of below 200 oC. [2-4] The SCFD furthermore also achieved conformal material deposition on substrate surfaces with complex geometry such as trench or hole structures, owing to the combination of high diffusivity and low viscosity of scCO2 fluid. [5]
In the present work, we report supercritical fluid deposition ofHfO2 films which is an important component as high-k gate insulator in thin-film transistors (TFTs) We expect that it contributes well to the low-voltage driving of TFT-based circuits on polymer or metal substrates.
The film processing was performed using a batch-type SCFD reactor consisting of a pressure-tight stainless steel vessel connected with CO2 fluid delivery and exhaust systems. Metal-organic (MO) precursors such as Hf(O-i-C3H7)4 and Hf(dipivaloylmethanate)4 were placed in the vessel with CO2 fluid and then the vessel was heated to promote the dissolution of MO in scCO2. The MO solution was then kept in the vessel with platinized silicon substrates to yield the deposition on substrate surfaces. The SCFD using Hf(O-i-C3H7)4 precursor yielded deposition of HfO2 films at a reaction temperature at 100 oC and above, which is significantly lower than those by other film-deposition method such as a CVD. The deposition rate was 22 nm/h and then it increased with the reaction temperature. Usage of alkoxide-based precursorslike Hf(O-i-C3H7)4 resulted in higher deposition rate rather than other precursors such as Hf(dipivaloylmethanate)4, owing to the promotion of hydrolysis and condensation for alkoxide compounds. Dielectric permittivity of 22 was confirmed for as-deposited HfO2 films, which was enhanced to 40 by additional post-treatment using scCO2.
[1] Watkins et al., Science, 294, 141 (2001).
[2] Uchida et al., Jpn. J. Appl. Phys., 44, 1901 (2005).
[3] Izaki et al., J. Ceram. Soc. Jpn., 124, 18 (2016).
[4] Shiokawa, et al., Mater. Res. Soc. Symp. Proc., 1729, 99 (2015).
[5] Kano et al., J. Supercrit. Fluids, 50, 313 (2009).
8:00 PM - EM10.05.27
Chemical Route Method to Synthesize Photoactive Nanoparticles of Lead Monoxide
Dharini Bhagat 1 , Manmohansingh Waldiya 1 , Indrajit Mukhopadhyay 1
1 , Pandit Deendayal Petroleum University, Gandhinagar India
Show AbstractTetragonal structured lead monoxide was synthesized chemically at elevated temperature from lead acetate and sodium hydroxide solution. XRD diffraction analysis revealed the crystalline alpha phase of powder, with an average particle size of 70nm and lattice constant a=3.97Å, b=3.97Å and c=5.02Å. An approximate value of phase transition from tetragonal to orthorhombic was obtained by comparing XRD data of lead monoxide powder annealed at various temperature within the range of 200°C -600°C. Direct band gap of 1.9 ev was confirmed by Uv-vis spectra analysis. Prepared lead monoxide powder with such properties, finds its promising application in energy conversion as well as energy storage.
8:00 PM - EM10.05.28
Structural and Optical Characterization of ZnWO4 Synthesized by Solution Based Process
Içamira Nogueira 1 , Magda Gondim 2 , Pablo Lemos 3 , Mario Soares 3 , Marcelo Assis 3 , Edson Leite 3
1 , UFAM, Manaus Brazil, 2 , IFMA, São Luís, Maranhão, Brazil, 3 , UFSCar, São Carlos, São Paulo, Brazil
Show AbstractTungstates with wolframite-type monoclinic structure, such as ZnWO4, have been studied because of their excellent properties for technological applications, such as solid state lasers, scintillators, electro-optical devices, microwaves, humidity sensors, photocatalysts and humidity sensors. However, few are the works that explores the relationship between the phase formation and the optical properties of this inorganic compound. Here we will describe the phase evolution as well as the photoluminescence behavior of this compound, synthesized by chemical solution process, more specifically, by the Polymeric Precursor Method (MPP). The phase evolution was performed by X-ray diffraction (XRD) with Rietveld refinement, Transmission Electron Microscopy (TEM) and Raman spectroscopy. The optical properties were characterized by Photoluminescent emission measurements and UV-Vis absorption spectroscopy. The results showed that in the amorphous state, formed at low temperature (bellow 550 oC), the materials shows a weak and broad emission centered at 450 nm. On the other hand, the fully crystallized material (single monoclinic phase), prepared at 700 oC, shows a strong emission, at 640nm. It is important to point out that the ZnWO4 material, processed by other synthetic routes, shows strong PL emission in the region of 500nm. The difference here observed can be associated to the presence of electronic defects that are formed during the genesis of this material.
8:00 PM - EM10.05.29
Hydrothermal Synthesis of Carbon Spheres and Corresponding Assembled Structures
Cefe Lopez 1 , Luz Karime Gil-Herrera 1 , Jose Angel Pariente 1 , Francisco Gallego-Gomez 1 , Felipe Gandara 1 , Alvaro Blanco 1 , Beatriz Huarez 2
1 , Instituto de Ciencia de Materiales de Madrid (ICMM, CSIC), Madrid Spain, 2 , Dep. Quimica Fisica Aplicada, Universidad Autonoma de Madrid, Madrid Spain
Show Abstract
Highly monodisperse core-shell carbon spheres in a size range between 500 and 900 nm can be grown by hydrothermal reaction from glucose in the presence of polystyrene seeds. Careful control over temperature, time, glucose concentration and seed size yields excellent hybrid spheres with no aggregation and no additional spheres population. Pyrolysis transforms the hybrid spheres in hollow carbon spheres with preserved monodispersity [1]. The PS@C spheres are very versatile systems, where control over the size of the core and the thickness of the shell provides a broad tunability of the optical properties of ordered 3D assemblies. This approach provides a basis to synthesize functional hollow carbon spheres with potential in photonics and energy applications. Additionally, a controlled methodology is presented capable to fabricate large-area high quality carbon-based opals in one-step from high these quality hybrid spheres [2]. An ulterior pyrolysis process eliminates the PS cores and slightly shrink the hybrid spheres, providing an extra way to further control the final optical response of the resulting structures, preserving the structural quality of the original ones.
[1] LK Gil-Herrera, Samll, 12, 4357 (2016)
[2] LK Gil-Herrera et al., Adv. Funct. Mater. to appear
8:00 PM - EM10.05.30
Smooth TiO2 Thin Films Grown by Aqueous Spray Deposition for Long-Wave Infrared Applications
Sarmad Alhasan 1 , Imen Rezadad 1 , Hussain Abouelkhair 1 , Vanessa Lowry 1 , Christopher Coleman 1 , Seth Calhoun 1 , Robert Peale 1 , Isaiah Oladeji 2 , Evan Smith 3 4 , Justin Cleary 3
1 , University of Central Florida, Orlando, Florida, United States, 2 , SISOM Thin Films, Orlando, Florida, United States, 3 Sensors Directorate, Air Force Research Laboratory (AFRL), Dayton, Ohio, United States, 4 , Wyle KBR, Dayton, Ohio, United States
Show AbstractSelf-assembled TiO2 film deposited by aqueous-spray deposition was investigated to evaluate morphology, crystalline phase, and infrared optical constants. The 130 nm thick film has Anatase nano-crystalline structure with ~10 nm characteristic surface roughness. The film is highly transparent throughout the visible to wavelengths of 12 micron. Important for long-wave infrared applications is that dispersion is weak compared with the more commonly used dielectic in planer structures SiO2. The low-cost, large-area, atmospheric-pressure, chemical spray deposition method would allow conformal fabrication on flexible substrates for long-wave infrared photonics.
8:00 PM - EM10.05.31
Formation of Lanthanum-Based Perovskite Compounds in Supercritical Water
Yoshiyuki Abe 1 , Iwao Satou 1 , Tsutomu Aida 2 , Tadafumi Adschiri 2
1 , Sumitomo Metal Mining Co Ltd, Ichikawa, Chiba-ken Japan, 2 , Tohoku University, Sendai, Miyagi-ken Japan
Show AbstractLanthanum-based perovskite compounds have been attractive recently as the catalysts for the energetic and environment applications. Generally, supercritical hydrothermal synthesis is known to be suitable for preparing fine and uniform metal oxide powders with high purity and high crystallinity in a single step without heating at high temperature. However, there are few reports concerning the direct synthesis of lanthanum-based perovskite compound by the supercritical hydrothermal synthesis; most of the compounds can be obtained through a solid-state reaction of the supercritical hydrothermal product at high temperature.
This study concerns the supercritical hydrothermal synthesis of the lanthanum-based perovskite compounds in a single step. From a nitrate solution containing La and Fe with adjusting its pH to 8.0, single phase of LaFeO3 was able to be obtained using a batch-type reactor vessel under the conditions of 30MPa and 450 °C for 15 min. Analysis of the products prepared by the lower reaction temperature or the shorter reaction period clarified a formation mechanism of LaFeO3; it was formed from a reaction of intermediate products of LaOOH and Fe2O3 at 450 °C, and LaOOH was formed through La2(OH)5.1(NO3)0.9 at the lower temperature. Moreover, second phase of La2(OH)5.1(NO3)0.9 and La(OH)3 were formed from the nitrate solution with the lower pH and the higher pH, respectively, even under the conditions of 30MPa and 450 °C. It can be said that the LaOOH intermediate product is key material to obtain LaFeO3 and the synthetic conditions of the nitrate solution pH of 8.0 and the reaction temperature of 450 °C are important synthetic conditions to form the LaOOH intermediate. By the above-mentioned optimized conditions, LaAlO3 was formed without a secondary phase, LaMnO3 was formed with secondary phases, and LaNiO3 and LaCoO3 were not able to be formed at all. In the presentation, we will discuss an origin of the ease with which these lanthanum-based perovskites are formed.
8:00 PM - EM10.05.32
High Performance, Low-Voltage, Solution-Processable Indium Oxide Thin-Film Transistors Using Anodic Al2O3 Gate Dielectric
Sagar Bhalerao 1 , Donald Lupo 1 , Paul Berger 1 2
1 Electronics and Communications Engineering, Tampere University of Technolog, Tampere Finland, 2 Department of Electrical and Computer Engineering , The Ohio State University, Columbus, Ohio, United States
Show AbstractTransparent electronics based upon metal oxide semiconductors is a major rapidly growing and promising technology for thin film electronics, especially printed electronics. The oxide semiconductors, especially the amorphous metal ones, made a remarkable progress in a relatively short time, challenging silicon not only in conventional applications but opening doors to completely new and disruptive areas like flexible and printed electronics. The special emphasis of metal oxide semiconductors, due to the high carrier mobilities, wide band gaps, broad transparency windows, tunable doping levels, and amenability to room-temperature film growth. Among metal oxides, In2O3 is a promising n-type semiconductor having a wide band gap (3.6-3.75 eV), high mobility [1]. Here we report the thin film transistor (TFT) fabrication by solution processable high-quality In2O3 thin films and anodic oxidized Al2O3 to form a dielectric.
TFTs with an indium oxide based semiconductors channel provides the added advantage of allowing for very low temperature processing. Oxide semiconductor based devices is a new technology that not only may replace the conventional silicon technology in some applications but also opens new areas of applications, probably faster than we can imagine or realize. Here we unite the device design, fabrication using very thin anodic Al2O3 dielectric testing to push the boundaries of lower temperature fabrication to reduce operating voltage, less than 5 volts. The TFT tested here exhibit field-effect mobilities as high as µsat = 3.5 cm2/V-1s-1, Ion/Ioff 105, turn on voltage 0.6 V and operate at 3.0 V.
The indium oxide TFTs were fabricated on glass substrates, with a bottom-gate top-contact TFTs were prepared on glass substrate. Initially, to form a gate contact 100 nm Al metal evaporated with a shadow mask, using a e-beam evaporator. The anodization process has been performed to form a good quality, pin hole free and room temperature aluminum oxide dielectric films [2,3]. The anodic aluminum shows an excellent dielectric property along with very dense barrier oxide films that can be grown on the substrates at room temperature [4]. Followed by a spin coating of indium oxide film [5], the samples were dried at 90°C on a hot plate in air for 15 min. and then annealed at 300 °C for 30 min. Finally, to 100 nm Aluminum were evaporated by using a shadow mask to form a drain – source contact. Electrical characterization was performed in using a keysight B1500A semiconductor device parameter analyzer.
REFERENCES
1. H. Kim, P. Byrne, A. Facchetti, and T. Marks, J. AM. CHEM. SOC. 130 (2008), 12580–12581
2. M. Kaltenbrunner, P. Stadler , R. Schwödiauer, A. Hassel, N. Sariciftci, and S. Bauer, Adv. Mater. 23 (2011) 4892
3. Feiyue Li, Lan Zhang, Robert M. Metzger, Chem. Mater, 10 (1998) 2475
4. D. Diesing , A. W. Hassel , M. M. Lohrengel ,Thin Solid Films, 342 (1999) 342
5. J. Leppäniemi , O. Huttunen , H. Majumdar , and A. Alastalo, Adv. Mater. 27 (2015), 7168–7175
8:00 PM - EM10.05.33
Using Polydisperse, near Micron-Sized TiO2 Particles for Color Generation
Kyungnae Baek 1 , Al-Mahmnur Alam 1 , Jieun Son 1 , Yi-Rong Pei 1 , Dong Ha Kim 1 , Jin-Ho Choy 1 , Jerome Hyun 1
1 , Ewha Womans University, Seoul Korea (the Republic of)
Show AbstractMonodisperse near micron-sized TiO2 particles appear white because they scatter light strongly and indiscriminately over the visible wavelengths due to their large size and high refractive index. In this work, we show that when assembled as a polydisperse collection, these ‘white’ particles can give rise to visible colors due to the weighted averaging of scattering over the size distribution. This is in contrast to the color generating mechanisms of subwavelength structures, where a collection of identical structures is demanded for generating well-defined colors. Furthermore, we explore the optical sensitivity of the polydisperse particles as a function of size and background index, and demonstrate their superior index sensing capabilities compared to other plasmonic or dielectric particles. The ability of TiO2 particles to impart color through a purely optical means, while preserving their chemical functionality, presents intriguing possibilities for their wide range of energy and device applications.
Symposium Organizers
Santanu Bag, Air Force Research Laboratory
Edward (Ted) Sargent, University of Toronto
Patrick J Smith, The University of Sheffield
Teodor Todorov, IBM T.J. Watson Research Center
Symposium Support
MilliporeSigma (Sigma-Aldrich Materials Science)
NovaCentrix
Strem Chemicals, Inc.
EM10.06: 2D Nanomaterials
Session Chairs
Santanu Bag
Tawfique Hasan
Mark Hersam
Wednesday AM, November 29, 2017
Hynes, Level 1, Room 103
8:00 AM - *EM10.06.01
Inorganic Two-Dimensional Nanomaterial Inks for Printed Electronics and Photonics
Mark Hersam 1
1 , Northwestern University, Evanston, Illinois, United States
Show AbstractLayered two-dimensional nanomaterials interact primarily via van der Waals bonding, which has created new opportunities for heterostructures that are not constrained by epitaxial growth [1]. In order to efficiently explore the vast phase space for van der Waals heterostructures, our laboratory employs solution-based additive assembly [2]. In particular, constituent two-dimensional nanomaterials (e.g., graphene, boron nitride, transition metal dichalcogenides, and black phosphorus) are isolated in solution, and then deposited into thin films with scalable additive manufacturing methods (e.g., aerosol, inkjet, gravure, and screen printing) [3]. By achieving high levels of nanomaterial monodispersity and printing fidelity, a variety of electronic, electrochemical, and photonic applications can be enhanced including digital logic circuits [4], lithium-ion batteries [5], and photodetectors [6]. Furthermore, by integrating multiple nanomaterial inks into heterostructures, unprecedented device function is realized including anti-ambipolar transistors [7], gate-tunable photovoltaics [8], and neuromorphic memristors [9]. In addition to technological implications for electronic and photonic technologies, this talk will explore several fundamental issues including band alignment, doping, trap states, and charge/energy transfer across two-dimensional van der Waals heterointerfaces [10].
[1] D. Jariwala, et al., Nature Materials, 16, 170 (2017).
[2] J. Zhu, et al., Advanced Materials, 29, 1603895 (2017).
[3] J. Kang, et al., Accounts of Chemical Research, 50, 943 (2017).
[4] M. Geier, et al., Nature Nanotechnology, 10, 944 (2015).
[5] K.-S. Chen, et al., Nano Letters, 17, 2539 (2017).
[6] J. Kang, et al., Nano Letters, 16, 7216 (2016).
[7] D. Jariwala, et al., Nano Letters, 15, 416 (2015).
[8] D. Jariwala, et al., Nano Letters, 16, 497 (2016).
[9] V. K. Sangwan, et al., Nature Nanotechnology, 10, 403 (2015).
[10] S. B. Homan, et al., Nano Letters, 17, 164 (2017).
8:30 AM - EM10.06.02
Screen Printing of Conductive Graphene Inks for Flexible Printed Electronics
Pei He 1 , Chongguang Liu 1 , Hui Ding 1 , Brian Derby 1
1 , Univ of Manchester, Manchester United Kingdom
Show AbstractThe development of high conductivity inks is critical to the progress of printed electronics. A promising conductive ink should fulfil high conductivity, long time stability, low cost, and compatibility with a range of substrates. For flexible applications, the printed conductive patterns also need good resistance to flexure and ability to withstand some extensional strain. Graphene, a two-dimensional allotrope of carbon, is a promising material for producing of conductive ink due to its high conductivity, good mechanical properties, and high-throughput production ability by solution processing. Graphene-based inks can be deposited to form conductive patterns through inkjet printing, gravure printing, and screen printing techniques.
In this work, we describe a high conductivity graphene ink suitable for screen printing that shows good flexibility. The graphene ink is prepared by dispersing few-layered graphene nanoplates in solvent using polyvinylpyrrolidone (PVP) as the stabilizer. The graphene films printed on polyimide (PI) substrates show a sheet resistance of 13.3 Ω/sq. at ~ 15 µm thickness with a drying temperature of 350 °C for 30 mins. With further treatment using compression rolling, the printed graphene films exhibit a sheet resistance of 5.3 Ω/sq. with thickness of ~ 2.5 µm, which offers a high electrical conductivity of ~ 7.55 × 104 S/m. In addition, the graphene films have been printed on polyethylene terephthalate (PET) and office A4 paper with a drying temperature of 120 °C. The compressed graphene films show sheet resistance of 7.9 and 8.5 Ω/sq. on PET and paper, respectively. Moreover, the graphene films also show very good flexibility on PI, PET and paper substrates. Thus, this high conductive graphene features through printing process and compatibility with various flexible substrates brings the possibility of using graphene as the conductive components in printed flexible electronics.
8:45 AM - EM10.06.03
Inkjet Printing Solution Processed 2D Materials—Influence of Flake Size on Coffee Ring Formation
Pei He 1 , Hamish Leith 1 , Brian Derby 1
1 , University of Manchester, Manchester United Kingdom
Show AbstractThe morphology of drops of graphene oxide (GO) inks produced by inkjet printing shows a distinctive coffee ring after drying when the mean diameter of the GO is below a critical size. Inks with larger diameter flakes do not show a coffee ring and the transition mean flake diameter decreases as the substrate temperature increases and when the printed drop size decreases. This behavior can be predicted with a model that compares the characteristic time for the agglomeration of high aspect ratio particles in suspension with the time scale for an evaporating liquid drop to begin receding during the drying process. The model is shown to accurately describe the transition from a coffee ring to a uniform dried deposit using a range of GO inks with mean flake size in the range 0.3 – 35.9 μm, drying temperatures of 20 – 60 °C, and drop sizes with contact diameter ranging from 30 – 800 μm.
Closer inspection of the structure of the coffee ring illustrates a secondary behaviour that is not fully explained by this simple model of the formation of a coffee ring. Careful image analysis of the distribution of graphene oxide flakes shows a statistically significant segregation of flake sizes within a coffee ring showing a larger fraction of small flake sizes close to the edge of the coffee ring at the original contact line. Mechanisms for this behaviour in terms of the presence of a free surface or the divergent nature of the fluid flow are considered and compared with the experimental results.
9:00 AM - EM10.06.04
Chemical Solution Processed MoS2 Channel Thin-Film Transistors with Nb-Zr-O Gate Insulator
Joonam Kim 1 , Ken-ichi Haga 1 , Eisuke Tokumitsu 1
1 , Japan Advanced Institute of Science and Technology, Ishikawa Japan
Show AbstractTransition metal dichalcogenides (TMDC) have attracted much attention as novel semiconducting materials for thin film transistor (TFT) applications. Fabrication processes for TMDC materials at present are mainly mechanical exfoliation and chemical vapour deposition (CVD) and there are only a few reports on chemical solution process. In addition, in most of the conventional reports, the TMDC layers were transferred to the high-k oxide films to fabricate TFTs. In this work, we have fabricated and characterized TFTs with MoS2 channel which was “directly” deposited on the high-k oxide gate insulator by the chemical solution process.
Source solution of (NH4)2MoS4 dissolved in N-methyl-2-pyrrolidone (NMP) was used in this work. The 0.05 mol/kg MoS2 source solution were spin-coated on oxide-coated Si substrates and annealed by a two-step annealing process, where the first annealing is performed at 450oC in H2/Ar (5:95) atmosphere for 20 min and the second annealing at 1000oC in Ar atmosphere with sulfur vapour for 20 min. We examined various oxide films of thermal stability during the 1000oC annealing with sulfur atmosphere and selected Nb-doped ZrO2(NZO) as a gate insulator. The Ti/Pt metal layer was used for source and drain electrodes. The gate electrode using Au was formed on the backside of the Si substrate. The channel length and width of the fabricated device are 10 and 50 µm, respectively.
We have measured Raman scattering spectrum of the channel region and confirmed the growth of MoS2 layers on the NZO gate insulator. In addition, conformal growth of a MoS2 layered structure on the curved surface of the NZO film was observed by transmission electron microscope. The number of layers of the MoS2 channel was over five layers in this study, although the thickness of the MoS2 layers can be reduced up to two molecular layers by diluting the source solution. We characterized transfer and output characteristics and confirmed n-type transistor operation. The on/off drain current ratio was 4.5x104 and the estimated field effect mobility was approximately 1 cm2/Vs.
9:15 AM - EM10.06.05
Gram Scale Production of Large Size 2D Crystals
Antonio Del Rio 1 , Alberto Ansaldo 1 , Filiberto Ricciardella 1 , Haiyan Sun 1 , Silvia Gentiluomo 1 , Vittorio Pellegrini 1 , Francesco Bonaccorso 1
1 , Fondazione Istituto Italiano di Tecnologia, Genova Italy
Show AbstractThe production of two-dimensional (2D) crystals is now facing the critical issue linked with the transition from the lab to the industry.[1] In fact, the exceptional properties of 2D crystals are stimulating the research activity in several application areas, ranging from polymer composites for healthcare to electronics.[1] However, the real-world application requires efficient synthesis methods.[2] Although many production techniques have been developed,[2] the most promising approach for large-scale production of 2D crystals relies on the liquid phase exfoliation (LPE) of their bulk counterparts.[3] However, the main limitations of LPE are the low production rate (g h-1) of 2D crystals, e.g., the ultra-sonication technique requires from 6 to 90 hours of processing time;[3] additionally, the material concentration in suspension is in the order of a few gL-1 [4,5], which means, for a 200 mL batch, or an average production rate of 1 g h-1. Higher production rates are achieved with the microfluidization (4-9 g h-1), if is compared with sonication.[6] However, concentrations of multilayer flakes in the 50 -100 gL-1 range can be achieved with the aid of surfactants,[6] whose presence is problematic for composites, electronic or biological applications.
To overcome the above-mentioned issues, we present a different approach for the exfoliation of bulk layered crystals in solution. The process is based on high pressure wet jet milling (WJM). This technique allows us to produce large quantities (>2L h-1, concentration >10 gL-1) at high production rate (~24 g h-1) of micron size single and few layer 2D crystal flakes in dispersion, without the aid of additives, i.e., surfactants. The WJM process is universal, i.e., it has been successfully applied to a large variety of layered crystals ranging from graphite, to hexagonal boron nitride, metal oxides, transition metal chalcogenides, and black phosphorus. A further purification step by centrifugation allows us to prepare dispersions highly enriched in few-layers flakes, keeping a concentration as high as 1 gL-1. We present the results obtained with the integration of the as-produced dispersions as functional inks for ink-jet, screen printing and spray coating suitable for different applications: graphene and MoO3 used as active material in lithium ion battery anodes, reaching a specific capacity of ~420 mAh g-1 (current density = 0.1 A g-1), as reinforcement in polyamide-hBN, and polyamide-graphene composites getting a 25% enhancement of the elastic modulus at 1 wt% of 2D crystal mass loading. Our 2D crystals production method opens the way towards their industrial exploitation.
[1] Ferrari, et al., Nanoscale, 7, 4598, (2015)
[2] Bonaccorso, et al., Mater. Today, 15, 564, (2012)
[3] Bonaccorso, et al., Adv. Mater, 28, 6136 (2016)
[4] Hernandez, et al., Nat. Nanotech, 3, 563, (2008)
[5] Nicolosi, et al., Science, 340, 1226419, (2013)
[6] Karagiannidis, et al., ACSnano, 11, 2742 (2017)
10:00 AM - *EM10.06.06
Functional Inks of 2D Materials for Optoelectronics and Photonics
Tawfique Hasan 1
1 , University of Cambridge, Cambridge United Kingdom
Show AbstractTwo-dimensional (2D) non-carbon materials such as semiconducting transition metal dichalcogenides (s-TMDs) and black phosphorus (BP) have attracted significant attentions in recent years because of their diversity and distinct optoelectronic properties. For example, high nonlinear susceptibility, ultrafast carrier dynamics and wide operation wavelength have enabled s-TMDs and BP to work as broadband saturable absorbers, albeit via different mechanisms compared to graphene. In addition to being saturable absorbers for photonics, these non-carbon 2D materials can also be used for a wide range of optoelectronic devices, including as transistors, photodetectors and sensors. Solution processability of these materials offers an exciting opportunity when applications are envisaged. As an inevitable extension to the requirements of solution processability, the ability to formulate their functional inks is of paramount importance for device-to-device performance variability.
I will discuss formulation of inkjet printable s-TMDs and BP inks and underscore the importance of using a mixed solvent approach for ink formulation without using any polymer binders. I will show that the choice of solvents enable reliable inkjet printing for scalable development of printed saturable absorbers and photodetectors. The printed BP works as a saturable absorber for ultrafast lasers without significant oxidative degradation, and can continue to operate for a prolonged period as a nonlinear saturable absorber under encapsulation. In combination with silicon-graphene schottky junction, the BP ink can be used as a sensitizer to fabricate visible to near-infrared photodetectors with high responsivities. I will also demonstrate that our functional ink platform can be used to fabricate simple photodetector device arrays of s-TMDs, with good device-to-device performance variability. Our approach to formulate these functional inks could also be exploited to develop binder free inks of other 2D materials for large-scale device arrays.
10:30 AM - EM10.06.07
Novel 2D Material Liquid Crystalline Composites as a Platform for Optoelectronic Devices
Benjamin Hogan 1 , Alexander Baranov 2 , Yulia Gromova 2 , Monica Craciun 1 , Anna Baldycheva 1
1 College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter United Kingdom, 2 , ITMO University, St Petersburg Russian Federation
Show AbstractLiquid crystalline nanocomposite materials are a novel class of hybrid fluid materials, which are currently attracting significant interest from the optoelectronics community due to their unique capability to interact with light, utilising many possibilities such as photoluminescence, plasmonics and quantum optics. Such nanocomposites are based on low-dimensional nanoparticles (carbon nanotubes, graphene, transition metal dichalcogenides (TMDCs), metal nanoparticles etc.) dispersed in a fluidic host material. Liquid crystalline properties can be accessed through the solvent-facilitated self-assembly of particles. The nanocomposites can be readily integrated on silicon chip by means of microfluidic technology allowing for dynamic control of the dispersed particles through the application of various on-chip stimuli1.
In this work, liquid crystalline nanocomposites have been synthesised based on two-dimensional (2D) materials including graphene oxide (GO) and TMDCs dispersed in various organic solvents. We demonstrate the emergence of the liquid crystal phase for different particle sizes, concentrations and solvents, across a range of different 2D materials. The variety of applications that emerge from the range of properties exhibited by the 2D materials used are considered. We discuss the factors affecting the observation of the liquid crystal phase and the range of materials for which such a phase is therefore possible. We consider the application of these materials in tunable self-assembly through the application of external fields by considering the achievable switching of the material properties, as observed through changes in the linear and circular dichroism of the materials. Importantly, we show that chirality can be induced during the ordered self-assembly of the nanoparticles.
1 B. T. Hogan, S. A. Dyakov, L. J. Brennan, S. Younesy, T. S. Perova, Y. K. Gun’ko, M. F. Craciun and A. Baldycheva, Sci. Rep., 2017, 7, 42120.
10:45 AM - EM10.06.08
Facile Routes to Solution Processed 2D Materials Beyond Graphene—Applications and Assembly of Hierarchical Structures
David Lewis 1
1 , University of Manchester, Manchester United Kingdom
Show AbstractGraphene is often made by the so-called Scotch Tape method, which produces small amounts of material for demonstrative studies of device performance. However, solution phase routes to two-dimensional (2D) materials such as liquid phase exfoliation (LPE) are attractive due to their potential scalability and compatibility with established processing techniques.
We are currently investigating a range of semiconducting 2D materials that are complementary to graphene and have recently produced a number of novel 2D semiconductor nanosheets including tin(II) sulfide (SnS), and black phosphorus (BP).[1,2] BP inks made by LPE in water have been used to fabricate electrochemical sensors for the cardiovascular disease biomarker myoglobin, with an extremely low limit of detection of 1.4 pg mL-1.[3] We have developed new processing routes toward nanosheet inks, combining bottom-up and top-down processing. Aerosol assisted chemical vapour deposition (AACVD) using single source precursors can deposit thin films of layered transition metal dichalcogenides, and we find it is relatively simple to incorporate dopant atoms into the structure using this process.[4] The resulting thin films can be subjected to LPE to produce colloids of novel, doped and exotic[5] transition metal chalcogenide nanosheets. The chemistry we have developed has also allowed integration of few-layer transition metal dichalcogenide nanosheets such as MoS2 into oxide structures produced by biological organisms[6] and ceramics with potential applications in catalysis and clean energy technologies.
[1] J. R. Brent et al. Chem. Commun. 50 (2014) 13338 . [2] J. R Brent et al. J. Am. Chem. Soc. 137, (2015), 12689. [3] V. Kumar et al. ACS Appl. Mater. Interfaces, 8, (2016), 22860. [4 ] D. J. Lewis et al. Chem. Mater. 27, (2015), 1367. [5] N. Al-Dulaimi et al. Chem. Commun. 52, (2016), 7878. [6] E. A. Lewis et al. Chem. Mater. 28, (2016), 5582.
11:00 AM - EM10.06.09
Optoelectronic Properties of Solution-Processed 2D Metal Carbides (MXenes)
Kathleen Maleski 1 , Mohamed Alhabeb 1 , Babak Anasori 1 , Yury Gogotsi 1
1 , Drexel University, Philadelphia, Pennsylvania, United States
Show AbstractTwo-dimensional (2D) materials are promising in optoelectronic and photonic applications due to the inherently flat morphology and diverse range of electronic properties from semiconducting transition metal dichalcogenides to insulating hexagonal boron nitride.1 Transition metal carbides and nitrides (MXenes) are a 2D material family with a general formula of Mn+1XnTx, where M represents a transition metal (Ti, Mo, Nb, V, Cr, etc.), X is either carbon and/or nitrogen, and Tx represents surface terminations.2 Titanium carbide (Ti3C2Tx) MXene has been shown to have high conductivity at high transparency (6500 S/cm, >97% transparency per-nanometer thickness), easily processed by spin or spray coating, and exhibits surface plasmon resonance in the visible to near-infrared range.3-4
Here, we will discuss recent progress and development of transparent, conductive MXene coatings and thin films beyond Ti3C2Tx, expanding the family of 2D optoelectronic materials. Moreover, because these are solution-processed materials, post-synthesis methods to control the lateral size will be discussed, such as sedimentation-based differential and density gradient centrifugation, to fabricate films with more monodisperse particles relative to the as-produced solution.
References
1. Xia, F. N., et al., Nature Photonics 2014, 8 (12), 899-907.
2. Anasori, B. et al., Nature Reviews Materials, 2017, 2(2), 16098.
3. Hantanasirisakul, K. et al., Adv. Electron. Mater. 2016, 2 (6), 1600050.
4. Dillon, A. D., et al., Adv. Funct. Mater. 2016, 26 (23), 4162-4168
11:15 AM - EM10.06.10
Two-Dimensional Ti2CTx Film for Large-Area Transparent Conductive Electrode Application
Yajie Yang 1 , Sima Umrao 1 , Shen Lai 1 , Sungjoo Lee 1 2
1 , Sungkyunkwan University Advanced Institute of NanoTechnology, Suwon Korea (the Republic of), 2 School of Electronics and Electric Engineering, Sungkyunkwan University, Suwon Korea (the Republic of)
Show AbstractMXene, an emerging class of 2D transition-metal carbides and carbonnitrides, has shown excellent conductivity and outstanding performance in many different applications. Here, we report a simple and scalable method to fabricate wafer-scale homogeneous MXene (Ti2CTx) transparent conductive thin film by dip coating of an Al2O3 substrate in a colloidal solution of large-area (mostly 10 µm) Ti2CTx flakes. Scanning electron microscopy and atomic force microscopy images exhibit the wafer-scale homogeneous Ti2CTx thin film (5 nm) covering the whole substrate. The sheet resistance is as low as 70 Ω/sq at 86% transmittance, which corresponds to the high figure of merit (FOM) of 40.7. Furthermore, the thickness of the film is tuned by a SF6+Ar plasma treatment, which can etch Ti2CTx film layer by layer. When top oxidized layer of MXene film was removed without affecting the bottom lay, the sheet resistance decreased to 63 Ω/sq with an improved transmittance of 89% and FOM of 51.3, demonstrating the promise of Ti2CTx for further transparent conductive electrode application.
11:30 AM - *EM10.06.11
Synergies of Solution Processed QD Materials and 2D Materials for High Performance Optoelectronics
Gerasimos Konstantatos 1 2
1 , ICFO, Castelldefels Spain, 2 , ICREA, Barcelona Spain
Show AbstractIn this talk I will present recent advances in the field of hybrid QD and 2D materials employed in high performance photodetectors [1,2]. I will overview the proof of principle underlying the hybrid phototransistor comprising such materials and then proceed with presenting advanced interface enginnering that has been employed to decouple the doping and environmental effects from the QDs to the 2D materials in order to simultaneously achieve high responsivity and sensitivity [3,4]. Then I will present results on hybrid 2D-QD phototransistors employing HgTe QDs that have allowed to reach record high sensitivities at SWIR wavelenghts beyond 2 um at room temperature operation[5].
The concept of transforming the photosensitizing layer of QDs from a passive to an active one, essentially turning it into a photodiode will be presented to demonstrate a phototransistor based on graphene and QDs with high sensitivity and fast response time[6].
I will conclude my talk showing some first prototypes based on this technology for wearable and imaging applications, including the first graphene-CMOS integrated broadband image sensor employing QDs that allow spectral coverage from 400 - 1800 nm [7].
References:
1. Nature Nanotechnol. 7, 363-368 (2012)
2. Adv. Mater. 27, 176–180 (2015)
3. ACS Photonics 3, 2197-2210 (2016)
4. ACS Photonics 3, 1324-1330 (2016)
5. Adv. Mater. 29, 1606576 (2017)
6. Nature Commun. 7, 11954 (2016)
7. Nature Photon. [online DOI: 10.1038/nphoton.2017.75] (2017)
EM10.07: Conductive Traces
Session Chairs
Santanu Bag
Patrick J Smith
Wednesday PM, November 29, 2017
Hynes, Level 1, Room 103
1:30 PM - *EM10.07.01
Patterning Liquid Metals at Room Temperature for Stretchable Electronics
Michael Dickey 1
1 , North Carolina State University, Raleigh, North Carolina, United States
Show AbstractThis talk will discuss efforts to pattern and characterize liquid metals as conductive inks for stretchable, soft, and reconfigurable electronics. Alloys of gallium are noted for their low viscosity, low toxicity, and negligible volatility. Despite the large surface tension of the metal, it can be patterned into non-spherical 2D and 3D shapes due to the presence of an ultra-thin oxide skin that forms on its surface. The metal can be patterned by injection into microchannels, direct-write techniques including 3D printing, or by inkjet printing colloidal suspensions. Because it is a liquid, the metal is extremely soft and flows in response to stress to retain electrical continuity under extreme deformation. By embedding the metal into elastomeric or gel substrates, it is possible to form soft, flexible, and conformal electrical components, stretchable antennas, and ultra-stretchable wires that maintain metallic conductivity up to ~800% strain. The ability of the oxide to reform instantaneously also allows the metal to self-heal in response to damage. This talk will focus on methods to pattern the metal at room temperature and the importance of processing conditions to achieve the desired patterns.
2:00 PM - EM10.07.02
Conductive Inks Composed of Self-Reducing Copper Formate Particles for 2D and 3D Printing
Yitzchak Rosen 1 , Shlomo Magdassi 1
1 Chemistry, Hebrew University of Jerusalem, Jerusalem Israel
Show AbstractFabrication of electronic devices by printing conductive interconnections on plastic substrates is of growing interest. Several approaches for the sintering of metallic nanoparticles (NP), mainly silver, were recently developed. However, the high cost of silver limits commercial use and therefore inks with low cost metals, such as copper, are required. Inks containing copper NPs suffer from stability problems, as the NPs are quickly oxidized, and so lose their conductivity. Therefore, there is an unmet need for a stable copper ink with a low sintering temperature.
Our research is aimed at printing conductive patterns by inks composed of sub-micron copper formate particles. Unlike inks with copper in its pure form, in this ink copper is present in a salt form, and so it is stable to oxidation, enabling a long shelf life. The ink can be easily screen-printed, and, upon thermal decomposition the salt is converted into conductive Cu° pattern.
Two approaches were investigated to induce decomposition of copper formate patterns, by photonic curing1, and by hot pressing2. With photonic curing, we found that decomposition can be controlled by the Intense Pulsed Light (IPL) parameters, and by controlling the absorptance of the ink. By adding as little as 0.5 wt % single-wall CNTs to the ink, the absorptance was enhanced by about 50% and the threshold energy required to obtain a conductive pattern was decreased by ∼25%. In hot-pressing, we found that applying pressure in addition to heat improved the obtained conductivity significantly. By this method, a printed sample was heated under high pressure for 10-30 minutes, resulting in patterns with 20% of bulk copper conductivity. This is an excellent improvement compared to conductivity of only 1% obtained by only heating the sample without pressure.
In addition, a new method3, Reactive Transfer Printing (RTP) was developed, based on transfer of an intermediate formed during decomposition of copper formate. The intermediate is released from a printed pattern, and migrates through the gas phase to a second adjacent substrate, forming a Cu° pattern. This method yielded excellent pattern morphology and conductivity, and can be used as a non-contact printing method for plastic and 3D electronics.
1. Rosen, Y. S., Yakushenko, A., Offenhausser, A., & Magdassi, S. (2017). Self-Reducing Copper Precursor Inks and Photonic Additive Yield Conductive Patterns under Intense Pulsed Light. ACS Omega, 2(2), 573-581.
2. Rosen, Yitzchak. Shlomo, et al. "Copper interconnections and antennas fabricated by hot-pressing printed copper formate." Flexible and Printed Electronics (2017).
3. Rosen, Y., Grouchko, M. and Magdassi, S. (2015), Printing a Self-Reducing Copper Precursor on 2D and 3D Objects to Yield Copper Patterns with 50% Copper's Bulk Conductivity. Advanced Materials Interfaces. doi: 10.1002/admi.201400448
2:15 PM - EM10.07.03
Metallic Nano/Micro Network Based Transparent Heater for Low Power Electronics Applications
Monee Roul 1 , Brandon Obasogie 1 , Kelsea Yarbrough 1 , Sangram Pradhan 1 , Messaoud Bahoura 1
1 , Norfolk State University, Norfolk, Virginia, United States
Show AbstractHeat generating transparent conductors finds interesting applications in optoelectronic devices like solar cells, wearable devices as well as defrosting and defogging in cold climatic conditions. Transparent conducting oxides (TCO) such as indium tin oxide (ITO) and Aluminium doped Zinc Oxide have been rampantly used in photoelectronic devices for decades, however their fragile ceramic nature limits their usage.
In order to overcome this limitation, we demonstrate fabrication of low power transparent thin film heaters based on metallic network of Ag nano/micro wires on glass. Colloidal solution of CeO2 was used to form crack sacrificial template onto which 250nm of Ag was deposited using electron beam evaporation technique. The seamless interconnected Ag mesh resembled artificial neural networks (ANN) and exhibited transmittance of ~80% and resistance of 30-40Ω. Application of a voltage as low as 3V generated a temperature of 150°C. Thus micro/nano metallic mesh based transparent heaters have potential applications in low power electronics.
This work is supported by the NSF-CREST Grant number HRD 1036494 and NSF-CREST Grant number HRD 1547771
3:30 PM - *EM10.07.04
Challenges for Copper-Plated Metallisation for Silicon Photovoltaics—Insights from Integrated Electronic Circuit History
Alison Lennon 1
1 School of Photovoltaic and Renewable Energy Engineering, UNSW, Sydney, New South Wales, Australia
Show AbstractToday more than 90% of the all the solar cells that are produced commercially have electrodes formed using screen-printed silver. As photovoltaic module costs decrease, the use of silver is increasingly under the spotlight as a way in which further cost reductions can be achieved. Silver remains the costliest non-silicon component in the crystalline silicon photovoltaic value chain contributing 5.2 US$ cents per 19.6% efficient cell in 2017 [1]. So far, moves to replace this silver with plated copper have failed to find traction, with several attempts to introduce plated copper metallisation into manufacturing being halted due to durability concerns or the plating process being not as cost-effective as the incumbent screen-printed metallisation process, despite the cheaper metal costs.
This situation may be considered surprising since electroplated copper has been used extensively in the fabrication of integrated circuits, with initial reports of the use of electroplated copper conductors for electronic circuits being traced back to early patents filed by Hanson (1903) and Ducas (1925) [2]. Furthermore, copper plating of n-type surfaces of the commonly-used p-type silicon solar cells can use the illuminated solar cell as a source of current to drive the deposition of metal directly to the silicon [3]. This can effectively eliminate the need to use seed layers and expensive sensitisers which are required to initiate copper plating to the silicon of integrated circuits. The search for effective seed metallisation strategies for integrated circuits largely provided the motivation for the development of electroless plating processes [2, 4].
The paper traces the history of copper plating for integrated electronic circuits and considers the parallels with copper plating for silicon solar cells. It identifies key roadblocks for a transition from silver to copper metallisation for photovoltaic applications and discusses how these roadblocks could be addressed.
References
[1] ITRPV, "International Technology Roadmap for Photovoltaic Results 2016," March 2017.
[2] K. Petherbridge, P. Evans, and D. Harrison, "The origins and evolution of the PCB: a review," Circuit World, vol. 31, pp. 41-45, 2005.
[3] A. Lennon, Y. Yao, and P. S. Wenham, "Evolution of metal plating for silicon solar cell metallisation," Progress in Photovoltaics: Research and Applications, pp. 1454-1468, 2012.
[4] J. Loiseleur, "Metallic coating," US Patent 2278722, 1942.
4:00 PM - EM10.07.05
Advanced Printing of Gallium Liquid Metal Alloys for Flexible and Reconfigurable Electronics
Christopher Tabor 1 , Alexander Watson 1 , Alexander Cook 1 , James Deneault 1
1 Materials and Manufacturing, Air Force Research Laboratory, Wright Patterson, Ohio, United States
Show AbstractRoom-temperature liquid metal alloys based on gallium are becoming ever more popular for reconfigurable and flexible electronic applications. Their low melting points and propensity to form an oxide skin enable them to be printed with high resolution using either bulk extrusion or aerosol jet printing of colloidal suspensions. We present several novel methods and materials that enable printing of these materials onto any substrate and in new form factors. One approach utilizes electrowetting to supplement the required surface adhesion to enable extrusion printing on any substrate with greater control and even onto vertical surfaces. Another achievement has been to utilize aerosol jet printing of novel colloidal dispersions of gallium liquid metal alloy for depositing liquid metal inks down onto nearly any surface with high resolution and high stand-off distances. Additionally, we demonstrate the ability to print barrier layers that allow the gallium liquid metal alloys to electrically connect to external electrodes without forming alloys with the electrode materials and demonstrate the mechanical integrity of these interconnects which will ultimately lead to robust stretchable and flexible electronic components.
4:15 PM - EM10.07.06
Fully Scalable Silver Nanowire Electrodes for Flexible Optoelectronics—Low Roughness, High Conductivity and Air Stabile
Richard Swartwout 1 , Farnaz Niroui 1 , Anna Osherov 1 , Giovanni Azzellino 1 , Markus Einzinger 1 , Vladimir Bulovic 1 , Marc Baldo 1
1 EECS, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractFlexible, lightweight optoelectronics will revolutionize how we think about display and energy generation technology and their use in the world. Displays can start resembling sheets of paper and kilowatts of solar cells that can be readily rolled up, transported, and installed. However, the realization of a flexible future requires a robust electrical and mechanical architecture. Unfortunately, most modern active layers have drastically different mechanical properties than surrounding metal electrodes conducting metal oxides, which leads to cracking in flexible substrates, limiting their use and increasing failure modes.
The distributed nature of silver nanowire meshes has proven effective at solving the mechanical discrepancy in many organic systems, but their high aspect ratios and oxidation in air have limited their overall use as a replacement for transparent oxides. Here, we develop a fabrication technique that utilizes solution processed spray coating and scalable chemical vapor deposition (CVD), to create a low cost and fully scalable Silver Nanowire and Parylene composite substrate that has near nanometer surface roughness, desirable optical and conductive properties, and stability in air comparable to high quality oxides. To date, we have fabricated Quantum Dot LEDs, Organic LEDs as well as Perovskite Solar Cells using this composite as the transparent conductor. Since these devices, including the nanowire composite substrate is 1/20th the size of a human hair, they can be laminated to any surface, expanding and reimaging their use.
4:30 PM - EM10.07.07
Reaction-Assisted Sintering of Inks for Printed Conductors
Sara Barron 1 , Jeffery DeLisio 1 , Peter Lewis 1 , Shashank Vummidi Lakshman 2 , Shane Arlington 2 , Timothy Weihs 2 , Brian Smith 1 , Greg Fritz 1
1 , Draper Laboratory, Cambridge, Massachusetts, United States, 2 , Johns Hopkins University, Baltimore, Maryland, United States
Show AbstractSignificant recent effort has been invested in inks for the preparation of conductive metal traces. The most mature of these ink formulations are composed of nano-sized particles of silver and, less commonly, gold. Critically, these elemental metals exhibit high diffusivities at moderate temperatures and negligible susceptibility to oxidation. Recent work to print copper traces has focused on sintering nano-sized copper or copper oxide particles in reducing or inert environments, either in the ink formulation or in sintering atmosphere, to eliminate the nascent oxides. However, these inks and the resulting conductive metal traces have relied on sintering mechanisms that lead to long term reliability concerns. Specifically, the inks are composed of nano-sized metal particles with high diffusivity so that they can be sintered into a continuous metal trace at moderate temperatures (often around 200°C) in short times (minutes to hours). The resulting conductive traces do not have bulk-like microstructures and instead form porous metal foams or nanograined structures that are susceptible to further microstructural, and hence performance, evolution at operational temperatures and times.
In this work, we present a new paradigm for printed conductive traces in which the metal ink formulation exhibits the necessary high diffusivity during sintering while simultaneously undergoing a phase transformation to a low diffusivity phase suitable for long term use. Specifically, the ink is composed of composite metal particles that, during sintering, undergo an exothermic phase transformation within and between the particles, resulting in an electrically continuous conductive line. We will discuss different composite particles that meet these criteria, including PVD synthesized Cu/Al nanolayered particles and ball-milled powders of Zr, C, and Al. For comparison, we have also considered the sintering of mixtures of elemental particles, such as mixtures of Cu and Al, Cu and Ag, and Al and C. Beyond material composition, the initiation of sintering and/or exothermic reaction is a key determinant of the final conductor’s microstructure and composition. For example, when the ink particles are heated slowly, such as in an oven or calorimeter (DSC, TGA), the exothermicity has a negligible effect on the particle temperature, and the nascent oxide and/or further oxidation of non-noble metal particles prevents sintering even in nominally inert atmospheres. In contrast, rapid heating, such as with a 833 nm laser or an intense pulsed light (IPL), can ignite a self-sustaining exothermic reaction, further raising the particle temperature and altering the competition between oxidation and sintering in favor of sintering. This balance can be further shifted by employing a reducing or inert environment from the ink formulation or atmosphere.
4:45 PM - EM10.07.08
Light Triggered Dissolution of Gold in Potassium Ferrocyanide for Degradable Electronics
Weida Chen 1 , Seung-Kyun Kang 2 , John Rogers 3 , Robert Grass 1
1 Chemical- and Bioengineering, ETH Zurich, Zürich Switzerland, 2 Bio and Brain Engineering, Korea Institute of Science and Technology, Daejeon Korea (the Republic of), 3 Materials Science and Engineering, Northwestern University, Evanston, Illinois, United States
Show AbstractTriggered transience has become a trait recent science has been focusing on with increasing interest.[1,2] Commonly used metals for transient electronic devices exhibit excellent dissolution properties but are in no way a substitution in their conductive properties to the industrially applied metals such as gold or copper.[3] Finding a way to dissolve those metals using a precursor would expand the repertoire of metals for transient devices.
In this study, we have used potassium ferrocyanide for the dissolution of gold. This material is regarded as a stable, non-toxic complex formed by iron in a cyanide containing solution; it can readily dissociate free cyanide ions upon exposure to UV light.[4] This attribute of potassium ferrocyanide, combined with the highly versatile and strong binding of cyanide to metals such as gold or copper leads to a light triggered degradation method for those metals.
Here we present first experimental data of a novel degradation method. The demonstration device, a gold electrode – 80 nm thick and 100 µm wide - immersed in a solution with potassium ferrocyanide, only shows an increase in resistance after switching on the UV light, eventually dissolving completely after 30 minutes. Apart from not being active in darkness, the dissolution rate can be tuned depending on the pH, potassium ferrocyanide concentration and irradiance, making it possible to arbitrarily customize the rate of degradation from seconds to several days.
A first application possibility of this chemistry as a simple and low cost UV detector is discussed in terms of performance, device scalability and environmental impact.
[1] C. W. Park, S.-K. Kang, H. L. Hernandez, J. A. Kaitz, D. S. Wie, J. Shin, O. P. Lee, N. R. Sottos, J. S. Moore, J. A. Rogers, S. R. White, Adv. Mater. 2015, 27, 3783.
[2] H. L. Hernandez, S.-K. Kang, O. P. Lee, S.-W. Hwang, J. A. Kaitz, B. Inci, C. W. Park, S. Chung, N. R. Sottos, J. S. Moore, J. A. Rogers, S. R. White, Adv. Mater. 2014, 26, 7637.
[3] L. Yin, H. Cheng, S. Mao, R. Haasch, Y. Liu, X. Xie, S.-W. Hwang, H. Jain, S.-K. Kang, Y. Su, R. Li, Y. Huang, J. A. Rogers, Adv. Funct. Mater. 2014, 24, 645.
[4] S. Ašpergěr, Trans. Faraday Soc. 1952, 48, 617.
Symposium Organizers
Santanu Bag, Air Force Research Laboratory
Edward (Ted) Sargent, University of Toronto
Patrick J Smith, The University of Sheffield
Teodor Todorov, IBM T.J. Watson Research Center
Symposium Support
MilliporeSigma (Sigma-Aldrich Materials Science)
NovaCentrix
Strem Chemicals, Inc.
EM10.08: Emerging Printing Techniques
Session Chairs
Santanu Bag
Patrick J Smith
Thursday AM, November 30, 2017
Hynes, Level 1, Room 103
8:15 AM - EM10.08.00
Transparent Metal Oxide Electrolyte-Gated Transistors
Irina Valitova 1 , Arunprabaharan Subramanian 1 , Yang Li 1 , Francesca Soavi 1 , Clara Santato 1 , Fabio Cicoira 1
1 , Ecole Polytechnique de Montreal, Montreal, Quebec, Canada
Show AbstractMetal oxide semiconductors, such as ZnO, SnO, In2O3, and indium gallium zinc oxide (IGZO), are of great interest for high-performance electronic devices that can be fabricated on large areas because of their transparency, ease of process, chemical stability and high n-type mobility. SnO2 is a very promising materials that already found applications in sensing, photovoltaic, optoelectronic devices and batteries.
We fabricated, both on rigid and flexible substrates, solution processed electrolyte-gated (EG) SnO2 transistors making use of high surface area activated carbon (AC), as a gate electrode, and the ionic liquid (IL) 1-Butyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)imide [EMIM][TFSI], as the gating media. Thin films of SnO2 have been deposited by sol gel and water based synthesis techniques and were photolithographically patterned as transistor channel materials.
We investigated bottom-contact top-gated transistor where we varied the area of the active layer in contact with electrolyte and the type of the electrolyte (ionic liquid vs lithium salts). To shed light on the doping mechanisms of such transistors we performed electrical measurements, cyclic voltammetry and electrochemical impedance spectroscopy. We demonstrated the performance of electrolyte- gated SnO2 transistors can be tuned via patterning of the metal oxide layer. Patterned EG SnO2 transistors work in depletion mode, while unpatterned ones work in enhancement mode with electron mobility as high as 10 cm2/Vs.
We believe that these simple device architectures working at low voltages are promising for low cost, flexible, transparent large area electronics.
8:30 AM - *EM10.08.01
Thin-Film Transistor Active Layer Deposition by Spray Pyrolysis
Veit Wagner 1
1 , Jacobs University Bremen, Bremen Germany
Show AbstractThere is large interest in establishing cheap, scalable processes for producing thin semiconducting layers for electronic applications. Furthermore low deposition temperatures are desirable to allow for a larger choice of suitable substrates, e.g. towards flexible substrates. One option here is wet chemical deposition by the spray coating or spray pyrolsis approach. Spraying is a suitable process for large area applications.
Materials can be deposited either via dissolved precursor molecules which react at the sample surface to the final product or by depositing the target material in form of preexisting dissolved nanomaterials. One example for the first approach is deposition of metal oxides from transition metal acetate precursor molecules. It is shown, that the timing of the spray coating as well as the substrate temperature, especially in relation to the solvent and surface dependent Leidenfrost temperature of the system, is crucial for high quality layer deposition.
Furthermore, post-growth modifications allow to remove transistor hystersis and potentialy existing sensitivity against bias stress. Deposition of 2D materials by spray coating, i.e. MoS2, is an example for the 2nd approach. An additional crucial step here is to produce well exfoliated dispersions suitable for deposition by spray coating. The latter can be achieved for MoS2 by a two step liquid phase exfoliation process usig N-methyl-pyrrolidone (NMP) and Isopropanol (IPA).
In summary, spraying is shown as low-cost and scalable solution-based fabrication process, which will promote thin film electronic applications in future.
9:00 AM - EM10.08.02
Printing without a Printer (Printerless Printing)—Functional Self-Organized Microstructures by Controlled Reaction-Diffusion-Precipitation
Artur Braun 1 , Rita Toth 1 , Edwin Constable 2 , Roche Walliser 2 , Istvan Lagzi 3 , Zoltan Racz 4
1 , Empa, Swiss Federal Laboratories for Materials Science and Technology, Duebendorf Switzerland, 2 Chemistry, University of Basel, Basel Switzerland, 3 , Budapest University of Technology and Economics, Budapest Hungary, 4 Physics, Eötvös University, Budapest Hungary
Show Abstract“Printing” typically boils down to synthesis and spatial allocation of droplets and particles after a given pattern. Synthesis and spatial arrangement of nano- and microparticles of different size is important in designing nanostructured materials with functional properties. Wet synthesis methods lack flexibility to create various sizes of particles (particle libraries) using fixed conditions without the repetition of the steps of the method with a new set of parameters. Here, we report a new method where we arrange particulates from a liquid by using the competition and interplay of diffusion, chemical reaction and subsequent precipitation [Toth 2016, Walliser 2015, Walliser 2016]. The patterns develop by self-organization and needs no further manipulation than initial allocation of chemical sinks and sources. The synthesis method is based on nucleation and particle growth in the wake of a moving chemical front in a gel matrix. The process yields well-separated regions (bands) filled with mono-disperse nano- and microparticles, with the size of particles varying from band to band in a predictable way. The smallest particle size which we can report is below 300 nm. The smallest band separation is 25 micrometer. This method represents a new approach and a promising tool for competitive, fast, up-scalable, low-cost printerless printing of various sizes of colloidal particles with magnetic, optical, electrical and catalytic properties.
[Toth 2016] Toth R, Walliser RM, Lagzi I, Boudoire F, Duggelin M, Braun A, Housecroft CE, Constable EC: Probing the mystery of Liesegang band formation: revealing the origin of self-organized dual-frequency micro and nanoparticle arrays. Soft Matter 2016, 12:8367-8374.
[Walliser 2015] Walliser RM, Boudoire F, Orosz E, Toth R, Braun A, Constable EC, Racz Z, Lagzi I: Growth of nanoparticles and microparticles by controlled reaction-diffusion processes. Langmuir 2015, 31:1828-1834.
[Walliser 2016] Walliser RM, Tóth R, Lagzi I, Mathys D, Marot L, Braun A, Housecroft CE, Constable EC: Understanding the formation of aligned, linear arrays of Ag nanoparticles. RSC Adv 2016, 6:28388-28392.
9:15 AM - EM10.08.03
Direct Write of Polymer-Bonded Magnets
Alan Shen 1 , Anson Ma 1 , Sameh Dardona 2 , Callum Bailey 2
1 Department of Chemical and Biomolecular Engineering, University of Connecticut, Storrs, Connecticut, United States, 2 , United Technologies Research Center, East Hartford, Connecticut, United States
Show AbstractPolymer-bonded magnets have recently gained popularity as a novel magnet manufacturing technique due to its low-cost, design freedom, and magnetizing patterns. The maximum energy product of polymer-bonded magnets is generally lower than that of sintered magnets. However, the fabrication of polymer-bonded magnets does not require high sintering temperature and thus can be more cost effective.
This presentation reports the use of a direct write (DW) 3D printing method with appropriate process controls to fabricate polymer-bonded magnets at room temperature. Additionally, the presentation will describe and discuss the ink formulation for controlled printing of conformal and 3D magnets. The performance of 3D-printed magnets will be presented and compared to those produced from other manufacturing methods.
10:00 AM - *EM10.08.04
How Solvent-Assisted Nanotransfer Printing Simultaneously Provides Sub-20 nm Resolution and Versatile Applicability for Diverse Functional Materials and Surfaces
Jae Won Jeong 1 , Jongmin Kim 1 , Hyeuk Jin Han 1 , Yeon Sik Jung 1
1 , KAIST, Daejeon Korea (the Republic of)
Show AbstractFlexible and stretchable electronics have recently attracted significant interest due to their extensive usefulness in diverse applications where conventional hard-substrate-based device platforms cannot be applied. For the realization of flexible electronics, device components such as transistors, transducers, and sensors should be formed on non-conventional surfaces such as flexible or curved substrates. Although nanotransfer printing (nTP) based on elastomers can provide a cost-effective and scalable processing route, remaining challenges include limited resolution (typically >100 nm), insufficient transfer yield, requirement of surface treatments, and so on. This talk introduces a novel solvent-assisted nanotransfer printing (S-nTP) strategy that can controllably generate extremely fine (down to sub-10 nm) functional nanostructures with excellent transfer yield (~100%). The spontaneous injection of solvent molecules into the interfaces between the thin film polymer replica and adhesive film enables facile switching of the interfacial adhesion and on-demand release of functional nanostructures on receiver substrates. S-nTP is compatible with various metallic, oxide, polymeric materials, as well as colloidal quantum nanostructures and is applicable to almost all surfaces including even biological surfaces. Moreover, S-nTP can be used for the uniform formation of single-crystalline nanostructures on various substrates. For instance, high-quality Si nanowires are patterned from low-cost bulk Si wafer and subsequently transplanted on to various non-conventional substrates by infiltration of a polymeric transfer medium and a dynamic adhesion switching mechanism induced by the incorporated solvent molecules. An extraordinarily large gauge factor was obtained with a strain sensor based on the single-crystalline Si nanowires. Furthermore, S-nTP makes it possible to construct highly uniform and reproducible 3-dimensional (3D) nano-architectures composed of high-quality crystalline materials. As an example, excellent catalytic activity and durability of 3D nanocatalysts will be demonstrated. Another manifestation of 3D geometry by S-nTP is multi-layer cross-point nano-plasmonic architectures, which provide an extremely high signal enhancement ratio for highly efficient surface-enhanced Raman spectroscopy (SERS). This new S-nTP platform with sufficiently high resolution and outstanding versatility can be exploited for high-throughput fabrication of future devices with novel functionalities, high integration density, and greatly improved performance.
10:30 AM - EM10.08.05
Aerosol-Jet Printing—A Means for Integrated Electronics and Photonics
Santanu Bag 1 2 , James Deneault 1 3 , Michael Durstock 1
1 , Air Force Research Laboratory, Wpafb, Ohio, United States, 2 , National Research Council, Washington, District of Columbia, United States, 3 , Universal Technology Corporation, Beavercreek, Ohio, United States
Show Abstract
The application of digital printing technologies for fabricating functional device components could bring competitive advantages in integrated electronics and photonics manufacturing sectors in terms of capital cost, production speed and product flexibility. A properly engineered ink with an appropriate printing process is essential to achieving these goals. Among different printing processes, ink-jet printing has shown promising digital capabilities. But as the nature and library of inks have become significantly more complicated over time, new printing techniques are beginning to emerge with unique capabilities. 3D automated aerosol-jet printing provides a relatively new capability to this field, offering a noncontact, direct, additive printing process, with unprecedented compatibility with a wide variety of inks, much higher material usage efficiency, accurate control of registration, and high resolution of the printed patterns. Here, we exploit the application of this technique to fabricate components of electronic and photonic devices, and relate the functionality and performance of the printed designs to their microstructures. We also show how the properties of both hard inorganic and soft polymeric materials can be harnessed in a single system by means of aerosol-jet printing.
11:00 AM - EM10.08.06
Fabrication of Yttrium Oxide Thin Film with High Dielectric Constant by Solution-Based Mist Chemical Vapor Deposition
Li Liu 1 , Misaki Nishi 1 , Phimolphan Rutthongjan 1 , Shota Sato 1 , Masahito Sakamoto 1 , Yusuke Kobayashi 1 , Ellawala Pradeep 1 , Giang Dang 1 , Toshiyuki Kawaharamura 1
1 , Kochi University of Technology, Kami Japan
Show AbstractFabrication of yttrium oxide (Y2O3) thin film at low temperature by a wet chemical method, using mist chemical vapor deposition (mist CVD) is demonstrated in this study. Recently, high dielectric (high-k) materials have received much attention because of their wide application prospect in microelectronic devices. Study of high-k materials is beneficial not only to solve the problem of the thin gate-oxide limitation in semiconductor devices, but also to prepare the new devices with special properties. In this study, we fabricate one of high-k materials, i.e. yttrium oxide thin film which is considered as a potential material for oxide dielectrics due to the excellent electronic properties, such as high dielectric constant (14~18), large band gap ( ~5.5eV), and high refractive index (1.7~1.9).
Usually, yttrium oxide thin films are fabricated using high deposition temperature or controlling the working pressure. However, we have developed a novel reaction supporting system in mist CVD, and yttrium oxide thin films can be fabricated at low temperature (400 °C) under atmospheric pressure. In our research, yttrium (III) acetylacetonate hydrate (Y(C5H7O2)3●nH2O) (n=2.36 as determined by TG-DTA) was selected as the precursor solute, and dissolved in methanol. Supporting materials were used to decrease the fabrication temperature while keeping the high properties. For controlling the atmosphere in reaction area of mist CVD, the precursor solution and supporting solution were set in different solution chambers. Using mist CVD with two solution chambers, we have obtained the yttrium oxide thin films with the deposition rate of 5.0 nm/min, and the refractive index of 1.77 using supporting materials, while, the thin films with deposition rate of 7.0 nm/min, and the refractive index of 1.65 were obtained without using supporting materials. In order to improve the properties of yttrium oxide thin films, we investigated the effect of the supporting material ratios on fabricating yttrium oxide thin films and studied the plausible mechanism of fabricating yttrium oxide thin films using mist CVD.
The details about fabrication of yttrium oxide thin film with high dielectric constant by mist CVD system will be presented in the conference.
11:15 AM - EM10.08.08
Patterning Metal Nanowire Based Transparent Electrodes by Seed Particle Printing
Muriel Tzadka 1 , Einat Tirosh 1 , Gil Markovich 1
1 , Tel Aviv University, Tel Aviv Israel
Show AbstractIn this lecture we present a unique combination of inkjet printing of functional materials with an intricate self-assembly process. Gold-silver nanowire (NW) mesh films were produced by a sequential deposition process, in which small metal seed nanoparticle film was deposited at desired areas by inkjet printing, followed by coating with a thin-film of NW growth solution. Two different types of NW growth solutions were used: the first, based on BDAC (benzylhexadecyldimethylammonium chloride), exhibited bulk solution growth mode and was thus suitable for coverage of large uniform areas. The second type was based on CTAB (hexadecyltrimethylammonium bromide), which induced NW growth confined to the substrate-solution interface and thus enabled patterning of small transparent electrode features, which have the same dimensions as the deposited seed droplets. A selective silver plating bath was used to thicken the ultrathin NWs, to stabilize them, and reduce the sheet resistance, resulting in films with sheet resistance in the range of 20-300 Ω/sq., 86-95% light transmission and relatively low haze. This simple patterning method of the NW film works at ambient conditions on many different types of substrates and has a potential to replace conventional photolithography used for indium tin oxide (ITO) patterning for applications such as touch sensors and flexible/stretchable electronics.
11:30 AM - *EM10.08.09
Functional Materials for 2D and 3D Printing
Shlomo Magdassi 1 , Michael Layani 1
1 , Hebrew University of Jerusalem, Jerusalem Israel
Show AbstractThe synthesis and formulations of nanomaterials, and their utilization as “inks” and for functional printing for and printed electronics will be presented. Recent discoveries of several routes for achieving high electrical conductivity of printed metal nanoparticles even at room temperature, which is important for plastics electronics will be discussed. These routes are based on various concepts of colloid and interface chemistry, such as coalescence and wetting processes that are observed in “coffee ring effect”. While combining the low sintering temperatures concepts with self assembly processes, transparent conductive plastic films can be formed, as demonstrated in optoelectronic devices such as electroluminescent films, tuch sensors and smart windows. Recent developments of new materials will be presented, in view of 3D and 4D printing, such as nano photoinitiators,shape memory printable polymers and CNT actuators.
EM10.09: Approaches for Flexible Applications
Session Chairs
Santanu Bag
Yeon Sik Jung
Patrick J Smith
Thursday PM, November 30, 2017
Hynes, Level 1, Room 103
1:30 PM - EM10.09.01
Water Based, Sinter-Free Inks of Metal-Polymer Hybrid Particles for Printed Electronics
Lola Gonzalez-Garcia 1 , Beate Reiser 1 , Johannes Maurer 1 , Indra Backes 1 , Juraj Drzic 1 , Tobias Kraus 1
1 , INM-Leibniz Institute for New Materials, Saarbruecken Germany
Show AbstractMetal-based nanoparticle inks are promising materials for printed electronics. Their inorganic cores provide good conductivity.[1] Nanoparticles in such inks are usually covered by organic ligands that provide colloidal stability and ensure the printability. When the particles get into contact upon drying, the ligand shells remain as insulating barriers. A sintering process is required to remove the organic component and ensure metallic contact. This process can cause compatibility problems with substrates or other printed components.[2]
Stabilizing ligands play a role on important properties of electronic inks that include shelf life, particle agglomeration during printing, and the electrical properties of printed patterns. An ideal ligand would provide stability, optimal nanoparticle packaging during drying, and low electrical resistance. We are exploring the use of conductive polymers as ligands for such ink.
Here, we present a sinter-free ink based on “hybrid” nanoparticles. Metal cores are coated with conductive polymer shells. A wet-chemical ligand exchange protocol strongly binds polythiophenes such as poly (3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) to the surface of the metal nanoparticles. We monitored the reaction by UV-vis and zeta-potential measurements where a charge reversal was observed from +25 mV to -40 mV. IR and Raman spectroscopy confirmed the ligand exchange. The stability of the hybrid particles was studied in a wide range of polar solvents and solvent mixtures and an inkjet-compatible ink was formulated. The ink exhibited a long shelf life of at least one year. After deposition, the conductive polymer ligands bridge the gaps between the inorganic cores and establish electrical contact. We prepared layers that yielded a specific conductivity of around 1.0 x 106 S/m immediately after drying.[3] The ink performed well on different substrates including glass, polymers, and paper. We are also investigating the use of sintering-free ink for flexible conductive composite materials, where hybrid conductive particles can be used as fillers in insulating polymer matrices.[4]
[1] J. Perelaer, P. Smith, et al., J. Mater. Chem., 2010, 40, 5432.
[2] A. Kamyshny and S. Magdassi, Small, 2014, 10, 3515.
[3] B. Reiser, L. Gonzalez-Garcia, et al., Chem. Sci., 2016, 7, 4190-4196.
[4] B. Reiser, T. Kraus, et al., Patent Application DE102015115549.4.
1:45 PM - EM10.09.02
Charge Carrier Generation in Photonic Hybrid Photovoltaic Films of Poly(3-Hexylthiophene)/TiO2 Inverse Opals
Jennifer Chen 1 , Nicholas Tulsiram 1 , Christopher Kerr 1
1 , York University, Toronto, Ontario, Canada
Show AbstractWe investigate three-dimensional photonic crystal as a potential active layer for bulk-heterojunction solar cells by fabricating a series of titanium dioxide inverse opals coated with poly(3-hexylthiophene). The photonic properties result in changes in the absorption profile of P3HT, where absorptance dips corresponding to the photonic stop bands and enhancements at both the red- and blue-edge due to slow photons are observed. The highly ordered porous structure of the inverse opal provides large interface between the P3HT donor and the TiO2 acceptor, and is effective at producing a high population of polarons compared to conventional P3HT/mesoporous-TiO2 and P3HT:PCBM films as probed by transient photoinduced absorption spectroscopy. The overall charge generation efficiency is dominated by the interfacial area of the P3HT-TiO2 inverse opals, and photonic enhancement is nominally achieved when the red edge of the photonic stop band overlaps with the irradiation. The charge generation efficiency can be further enhanced by several-fold by modifying the oxide and polymer interface. The interplay of the multifaceted factors governing the charge generation of the macroporous structure will be discussed. The findings of this work provide fundamental insights on the incorporation of 3D colloidal photonic crystal as the bulk heterojunction active layer in organic and related hybrid photovoltaics.
2:00 PM - EM10.09.03
Stretchable Antiscratch Coating Film Prepared by Organic-Inorganic Sol-Gel Process
Hyeok-jin Kwon 1 , Chan Eon Park 1 , Se Hyun Kim 2
1 Chemical Engineering, Pohang University of Science and Technology, Pohang Korea (the Republic of), 2 Advanced Organic Materials, Yeungnam University, Gyeongsan Korea (the Republic of)
Show AbstractThe development of hybrid organic-inorganic materials has been extensively studied in recent years. These materials show the combining properties of organic and inorganic components through the combination of a wide variety of compositions. So, applications may be found in the area of protective coatings, e.g. corrosion-resistant, scratch- and wear-resistant materials combined with future flexible electronics.
Herein, we developed the stretchable, transparent and scratch-resistant coating film using the hybrid organic-inorganic material. The hybrid organic-inorganic material was fabricated by mixing of inorganic components (Silica and Titania) and organic components (amphiphilic polymer named ASAP). The addition of amphiphilic polymer, ‘ASAP’, can make solution stable since it surrounds the inorganic particles (Silica and Titania nanoparticle) like surfactant material to prevent gelation (hydrolysis of Silica and Titania) and give the flexibility to coating film to bond each inorganic domain. The coating film was made by sol-gel process using slot-die coating on CPI(colorless Polyimide). The coating film was investigated using several test methods including UV/VIS spectrophotometer, Haze, pencil hardness, and stretching property. The transmittance in 400nm~800nm (visible ray area) was as high as 90% and the haze of coating film was 0.84. The pencil hardness was as high as 3H and elongation strain 5% are achieved. The present approach to scratch-resistant coating offers a much easier and simpler way than the conventional ones, which require multi-step coating. Also it can set the stage for the replace of glass in flexible electronics
2:15 PM - EM10.09.04
Printed Organic Photodetectors and Scintillator Inks for X-Ray Indirect Radiation Detection
Juliana Oliveira 1 , Enrico Sowade 2 , V Correia 1 , Kalyan Mitra 2 , Ikerne Etxebarria 3 , Gerado Rocha 1 , Reinhard Baumann 2 , Senentxu Lanceros-Mendez 3 1
1 , Universidade do Minho, Vila Nova de Famalic Portugal, 2 , TU Chemnitz, Chemnitz Germany, 3 , BC Materials, Bilbao Spain
Show AbstractX-ray imaging has been increasingly used in many fields ranging from security control to industrial and medical diagnostics. There is increasing interest on alternative materials and concepts for innovative radiation detection basically aiming in larger areas, flexibility and increased sensitivity. Further, traditional techniques based on X-ray film processing have been quickly replaced by digital imaging techniques which show some advantages [1]. The improvement of image quality or enhancing the capability for imaging processing and analysis are some examples. However, the growing demands of flexibility, low-cost and scalable technologies leads to the development of printed detectors that will reduce the limitations caused by the rigid panels of conventional detectors and allow a better integration of these kind of sensors into a large variety of applications [2]. Inkjet printing represent an additive manufacturing technique very attractive for rapid prototyping of “plastic electronics” [3] and appears as a good manufacturing method for the development of flexible and low-cost smart and functional materials [4, 5]. The development of inkjet printed organic photodetectors for X-ray imaging applications, suitable for integration in an image sensor array will be presented. The development of low cost and flexible fully inkjet printed organic photodetectors based on a p-type semiconductor will be shown, as well as their performance as X-ray indirect radiation detectors. For the later, a high performance a scintillator inks based on a thermoplastic elastomer Styrene-Ethylene/Butadiene-Styrene (SEBS) and Gd2O3:Eu3+ scintillator nanoparticles has been developed and placed on top of the photodetectors.
[1] D. Gavrilov, R. G. Maev, D. P. Almond, Canadian Journal of Physics 2014, 92, 341.
[2] B. J. Kang, C. K. Lee, J. H. Oh, Microelectronic Engineering 2012, 97, 251.
[3] B. Ando, S. Baglio, IEEE Sensors Journal 2013, 13, 4874.
[4] S. Chung, S. O. Kim, S. K. Kwon, C. Lee, Y. Hong, IEEE Electron Device Letters 2011, 32, 1134.
[5] G. Pace, A. Grimoldi, M. Sampietro, D. Natali, M. Caironi, Semiconductor Science and Technology 2015, 30.
3:00 PM - EM10.09.05
Metal Nanowires for Printed Electronics
Benjamin Wiley 1 , Ian Stewart 1 , Matthew Cattenacci 1 , Mutya Cruz 1
1 , Duke University, Durham, North Carolina, United States
Show AbstractThis presentation will focus on how the high aspect ratio of nanowires, as well as control over their surface composition, can be used create better materials and devices for printed electronics. Their long lengths (tens of microns) and small diameters (tens of nanometers) allow nanowires to traverse relatively large distances while occupying small volumes. These attributes can allow an interconnected network of nanowires to conduct electrons while blocking little visible light. For example, thin films of silver and copper nanowires are highly conductive (<100 ohm sq-1) but transmit 99% of visible light. The long lengths of nanowires also serve to reduce the number of contacts between particles, enabling films of silver nanowires to be up to 4000 times more conductive than films of silver nanoparticles. By coating thin shells on nanowires, one can imbue a physically thick material with the electrical properties of a physically thin material. This technique was use to create the first fully-printed non-volatile memory with properties comparable to flash memory. Nanowire shells can also imbue an abundant and inexpensive material with the properties of a rare and costly material. For example, we will report how to coat thin shells of noble metals such as gold, silver and platinum onto copper nanowires without galvanically etching the copper nanowires. The synthesis of silver-coated copper nanowires has been scaled up to enable the production of a conductive filament for 3D printing that is 400 times more conductive than carbon-based filaments. We will illustrate how such a conductive filament can be used to produce 3D printed electronics and antennas with low-cost FDM 3D printers. The structure-property studies and applications presented here will illustrate that we are only beginning to take advantage of the unique attributes of nanowires for printed electronics.
3:15 PM - EM10.09.06
Highly Stretchable, Flexible and Transferable Label-Like Random Lasers on Universal Substrates
Yu-Ming Liao 1 , Wei-Cheng Liao 1 , Cheng-Han Chang 1 , Yuan-Fu Huang 1 , Hung-I Lin 1 , Ying-Chih Lai 2 , Yang-Fang Chen 1
1 Physics, National Taiwan University, Taipei Taiwan, 2 , National Chung Hsing University, Taichung Taiwan
Show AbstractRandom lasers are produced by the feedback of the mirror-free scattering media, unlike conventional laser devices that require rigid optical resonator to form closed lasing loop. Such extraordinary phenomenon endows specific benefits in random lasers. Advantages of random lasing devices include small sizes, broad-angular emission, flexible probability, simple device structures, low cost and large-area manufacturability, which has high potential in application on display devices, sensors, medical diagnostics as well as information and forensic technologies. Random lasers are also considered as a promising candidate for flexible lasing light source. On the other hand, future electro-photonic modules are expected to possess functionalities such as lightweight, portability, flexibility and even stretchability. Electro-photonic systems could deform freely will further increase their applications in vast fields, such features are hard to be reached by conventional lasers. Random lasers have been considered as one of the promising devices to become the lasing light sources for flexible electronics. Most devices were fabricated only on rigid, flat and plastic substrates, which limits their promising applications tremendously. Traditional fabrication approaches for random lasers were constructed by the bottom-up schemes, in which the substrates were pre-determined and restricted by the processing conditions, chemical solvent compatibility, and handling requirements. Such restrictions lead to difficulties in processing random lasers on desired objects and limit their superiority in applications extremely. Moreover, the measured signals on tested substrates will be altered when processing devices physically due to the unpredicted lasing loops, which leads to a fatal issue for applications of random lasers. Alternatively, a promising strategy is to carry out the fabrication processes on a conventional planar substrate and further transfer pre-prepared devices onto desired objects such as rigid, flexible, non-planar and rough substrates to avoid unsuitable fabricating processes while, importantly, keeping the lasing signals. Here we present a newly-designed label-like thin and highly stretchable random lasing device that can be facially transferred and stacked on arbitrary substrates. These unprecedented features allow the random laser device to apply on desired objects, including irregular and soft ones, while keeping its lasing characteristics for the first time. Moreover, based on the unique attributes of transferability and thin (~2 μm), our random laser shows high stretchability of over ~100 %. The presented stratage can provide an effective way to create lasing light in flexible and arbitrary substrates. It can be foreseen that that our devices will open a new perspective of random laser devices and will be beneficial in vast fields of nextgeneration flexible optoelectronics ranging from conformable lasing sources to implantable opto-electronic systems.
3:30 PM - EM10.09.07
Intercalated Graphene—PbS Quantum Dot Hybrid Photodetectors for Enhanced Photocarrier Collection
Wenjun Chen 1 , Xiaochen Li 1 , Oscar Vazquez-Mena 1
1 , University of California, San Diego, La Jolla, California, United States
Show AbstractPbS quantum dots (QDs) are promising materials for photodetector due to their size-tunable band gap, strong light absorption and low cost solution processing[1][2]. However, the short diffusion length (~200 nm) results in low charge collection efficiency that limits the photoresponsivity[3]. Recently, hybrid graphene quantum dot (Gr/QD) systems have emerged as high-response photodetectors[4–6]. Such systems have been limited to a top layer QD film on a single graphene layer. In this work, we present a novel architecture that incorporates multiple intercalated graphene layers inside the QD film. The intercalated graphene layers ensure a faster and more efficient carrier collection to enhance the performance of the device, especially in the near-infrared range that requires deeper absorption depths and therefore thicker films. This architecture allows efficient charge collection in films thicker than carrier diffusion length.
The intercalated Gr/QD devices were made by sequential Gr wet transfer and QD spin coating on SiO2/Si substrate. We demonstrated high device conductivity because each graphene adds an extra conductive channel, 10L intercalated Gr/QD devices have sheet resistance of 100 W/sq while the 10L device with single Gr sheet shows 2.2 kW/sq. Furthermore, we demonstrated an enhanced photoresponse compared to single graphene devices, especially at near infrared spectral range (from 700 nm to 1100 nm). Single layer devices show a tradeoff between visible and near infrared response, whereas our devices show much higher photoresponse in both ranges. For a 200 nm thick QD film under illumination with a 1.2mW laser at 635 nm, the photocurrent of intercalated Gr/QD device is 100 mA while the non-intercalated device gives a 10x lower response of 11 mA. These intercalated Gr/QD photodetectors can be operated in low bias regime with high photoresponse output, which is compatible with silicon integrated circuits.
This work demonstrates the first intercalated Gr/QD hybrid photodetectors, introducing a new approach to achieve high light absorption and efficient charge collection in high-response photodetectors. Our intercalated electrode approach allows breaking the restriction that diffusion length imposes on the thickness of QD layers and paves the way for the development of high response photodetection devicesReferences:
[1] R. Saran, R. J. Curry, Nat. Photonics 2016, 10, 81.
[2] X. Lan, S. Masala, E. H. Sargent, Nat. Mater. 2014, 13, 233.
[3] G. H. Carey, A. L. Abdelhady, Z. Ning, S. M. Thon, O. M. Bakr, E. H. Sargent, Chem. Rev. 2015, 115, 12732.
[4] G. Konstantatos, M. Badioli, L. Gaudreau, J. Osmond, M. Bernechea, F. P. G. de Arquer, F. Gatti, F. H. L. Koppens, Nat. Nanotechnol. 2012, 7, 363.
[5] Z. Sun, Z. Liu, J. Li, G. A. Tai, S. P. Lau, F. Yan, Adv. Mater. 2012, 24, 5878.
[6] I. Nikitskiy, S. Goossens, D. Kufer, T. Lasanta, G. Navickaite, F. H. L. Koppens, G. Konstantatos, Nat. Commun. 2016, 7, 11954.
3:45 PM - EM10.09.08
Eutectic Gallium-Indium Liquid Metal Contacts on Printed Carbon Nanotube Thin-Film Transistors
Joseph Andrews 2 , Kunal Mondal 1 , Michael Dickey 1 , Aaron Franklin 2 3
2 Electrical and Computer Engineering Department, Duke University, Durham, North Carolina, United States, 1 Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States, 3 Department of Chemistry, Duke University, Durham, North Carolina, United States
Show AbstractPrinted electronics have gained significant attention due to their numerous advantages including low-cost, high manufacturability, and applicability for large surface area sensors or systems. Moreover, the printing approach itself is substrate agnostic, leading to significant potential for flexible and stretchable electronics. Advances related to polymeric or ultrathin inorganic transistors have provided solutions to flexible and even foldable electronics, but the ability to stretch without reduced performance remains a noteworthy challenge for complex electronic devices. One key limitation to realizing stretchable electronics is the degradation that occurs at the metal-semiconductor contact interfaces owing to the use of rigid metal contact films. Liquid metals offer a promising solution for this challenge but have received limited consideration for how well they can function as contacts in thin-film transistors. The auspicious combination of semiconducting carbon nanotubes (CNTs) with liquid metal contacts has substantial potential in realizing fully printed, stretchable electronics.
In this work, we present printed devices employing liquid metal as the source and drain contacts for substrate-gated CNT thin-film transistors (TFTs). First, semiconducting carbon nanotubes (> 99% purity) were printed using an aerosol jet printer onto a silicon substrate with a 300 nm SiO2 oxide layer. Next, liquid metal (eutectic Gallium-Indium) was deposited using two distinct methods, each studied in detail: 3-D printing and vacuum filling. The contact resistance and transistor operation for each deposition method was analyzed and compared. Other variables that were also explored include in-situ and post-deposition annealing. One key observation was the low adhesion between the liquid metal and CNT film. Hence, techniques were explored for promoting better adhesion, including the use of a sparsely printed Ag nanoparticle layer directly onto the carbon nanotube channel. The highest performing transistor was realized using liquid metal contacts that were deposited by vacuum filling PDMS microchannels at 150 ºC. This device exhibited an on-off ratio of > 104, and an on-current of 150 µA/mm at VDS = -5 V with a channel length (Lch) of 200 µm. The contact resistance from the vacuum-filled microchannel metal electrodes was found to be approximately 50% lower than the contact resistance associated with the 3-D printed liquid metal contacts. To our knowledge, this is the first demonstration of a CNT-TFT with liquid metal as the contacts and motivates further research towards the possibility of fully-stretchable, printed electronics.
4:00 PM - EM10.09.09
Soft Microreactors for the Solution-Phase Deposition of Conductive Metallic Traces on Three-Dimensional Components for Electronics
Abhiteja Konda 1 , Advaith Rau 1 , Michael Stoller 1 , Gabriel Pribil 1 , Stephen Morin 1 2
1 Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska, United States, 2 Nebraska Center for Materials and Nanoscience, University of Nebraska–Lincoln, Lincoln, Nebraska, United States
Show AbstractAdvanced manufacturing has enabled efficient and economical production of electronic circuits that are used in a wide range of consumer devices (from simple toys to complex computing systems); however, the interconnects for these circuits are predominantly produced using top-down lithography on planar surfaces (i.e., printed circuit boards). The use of solution-phase techniques to deposit functional inorganic materials directly onto target substrates selectively will provide simple, inexpensive processing opportunities, especially for devices with non-traditional form factors that are currently manufactured using complicated methods such as laser directed structuring. We demonstrated the deposition of conductive copper traces (via localized, flow-assisted, low-temperature, electroless copper deposition) onto 2D/3D polymeric components of arbitrary geometry, chemical composition, and/or texture using soft microreactors that can be reversibly sealed to the target components. These traces, when combined with various off-the-shelf components, are generally applicable to a variety of electronic circuits (e.g., simple displays and sensors). Our approach to the patterned metallization of 2D/3D polymeric substrates is applicable to the fabrication of 3D “molded interconnect devices” (MID’s), and other free-form electronic devices, which offer unique design opportunities and weigh less. Additionally, the strategy we demonstrated, which makes use of low-cost, solution-phase processing offers potentially scalable options for manufacturing such devices.
4:15 PM - EM10.09.10
Epitaxial Electrodeposition of Inorganic Semiconductors onto Wafer-Size Single Crystal Gold Foils for Flexible Electronics
Naveen Mahenderkar 1 , Jay Switzer 2
1 Materials Science and Technology, Missouri University of Science Technology, Rolla, Missouri, United States, 2 Department of Chemistry, Missouri University of Science and Technology, Rolla, Missouri, United States
Show AbstractSingle-crystal Si is the bedrock of semiconductor devices due to the high crystalline perfection which minimizes electron-hole recombination, and the dense SiOx native oxide which minimizes surface states. To expand the palette of electronic materials beyond planar Si, an inexpensive source of highly ordered material is needed that can serve as an inert substrate for the epitaxial growth of grain boundary-free semiconductors, photonic materials, and superconductors. We have recently shown that wafer-size transparent and flexible single-crystal foils of Au can be produced by a simple and inexpensive lift-off procedure using single-crystal Si as the template for electrochemical epitaxial growth.1 The Au foils offer the order of traditional single-crystal semiconductors without the constraint of a rigid substrate. A 28-nanometer-thick gold foil with a sheet resistance of 7 ohms per square showed only a 4% increase in the resistance after 4000 bending cycles. Here, we explore the epitaxial growth of inorganic semiconductors such as Cu2O, CdTe, and ZnO onto single crystal Au foils using electrodeposition. We compare the electronic properties of these ordered films to both textured and polycrystalline materials.
References:
[1] N. K. Mahenderkar, Q. Chen, Y.–C. Liu, A. R. Duchild, S. Hofheins, E. Chason, and J. A. Switzer, “Epitaxial lift-off of electrodeposited single-crystal gold foils for flexible electronics,” Science 355, 1203 (2017).
4:30 PM - EM10.09.11
Metallic Embedded Nanomesh as Transparent Electrode Fabricated by Template-Based Electrodeposition for Flexible Electronic Devices
Arshad Khan 1 , Cuiping Zhang 1 , Wen-Di Li 1 , Shien Ping Feng 1
1 , The University of Hong Kong, Hong Kong Hong Kong
Show AbstractEmerging flexible electronic devices such as flexible solar cells, displays, and touch panels need transparent conductors (TCs) with high mechanical flexibility in addition to high optical transparency and electrical conductivity. To accomplish these requirements, new-generation TCs based on carbon nanotube, graphene, metal nanowire networks, and metal mesh are comprehensively studied recently. In particular, TCs based on metal mesh are leading candidates due to their regular structure, excellent electrical conductivity, and flexibility. However, widespread adoption of metal-mesh based transparent electrodes has been limited by several key issues such as expensive vacuum-based metal deposition from the vapor phase, non-flat surface topography and weak adhesion between the metal mesh and flexible substrate. We addressed the above-mentioned issues in our latest report [1] by introducing the “embedded metal-mesh transparent electrode” (EMTE) structure featuring a micro-metal mesh fully embedded and mechanically anchored in a flexible substrate, and a solution-based fabrication strategy involving lithography, electroplating, and imprint transfer (LEIT) for its production. Despite the advantages offered by the EMTEs, key intrinsic issues of wide linewidths (few microns) and large open spaces (tens of micron) still remained in its structure which cause electrical non-uniformity and is highly undesirable for effective carrier transportation in many electronic devices. Also the LEIT comprises a mandatory lithography step in making each sample which limits its suitability for high-throughput and large-volume industrial production and needs further simplifications.
Here, we propose an improved and facile fabrication process based on templated electrodeposition for making nano-EMTEs. First, electrodeposition templates with nano features are prepared by nanowire lithography where nanowires are used as masks to etch into the underlying 100 nm thick SiO2 film on ITO glass substrate. The nano-EMTEs are then fabricated by selectively depositing 500 nm thick metal in the trenches of the nanomesh patterns by electrodeposition. This nano metal-mesh is subsequently transferred from the template to the polymer substrate by UV imprint transfer process. The prototype EMTEs exhibited an optical transmittance higher than 80 % and sheet resistance lower than 1 ohm/sq. Furthermore, it can be bent to 3 mm radius of curvature with negligible degradation of conductance. In the preliminary reusability tests, SiO2 based template shows no noticeable degradation after 10 uses and therefore is a promising candidate for reusable template for large-scale manufacturing of nano-EMTEs. The promising electrical and optical properties of our nano-EMTEs offer the potential use in many flexible electronic devices that we are currently investigating.
[1] A. Khan, S. Lee, T. Jang, Z. Xiong, C. Zhang, J. Tang, L. J. Guo, W.-D. Li, Small 12, 3021 (2016).
4:45 PM - EM10.09.12
All Water-Based Solution Process for Metallic Nano-Mesh Transparent Electrodes
Sung Min Lee 1 , Byoung Joon Park 1 , Suk Tai Chang 1
1 Chemical Engineering and Materials Science, Chung-Ang University, Seoul Korea (the Republic of)
Show AbstractTransparent conducting electrodes have attracted substantial attentions as an essential component of various optoelectronic devices. Random networks of conducting nanomaterials for the production of transparent conducting electrodes have been fabricated by applying various conventional methods for colloidal assembly, such as spin-coating, spray-coating, vacuum filtration, and rod coating. Although the random networks of conductors presented relatively good optoelectronic properties, there is a trade-off between electrical conductivity and optical transmittance in this random material geometry. Recently, the grid-structured metal mesh electrodes are considered as highly efficient transparent electrodes that possess high optical transmittance while maintaining sufficient electrical conductivity and are suitable for stretchable conductors with isotropic electrical conductivity. Here, we report a simple and effective approach for the fabrication of highly transparent metallic nano-mesh conducting electrodes prepared by all water-based solution process. The metal mesh electrodes were formed by silver enhancement on gold nanoparticles dip-coated on APTES pre-patterned substrates. The optical and electrical properties of the metal mesh electrodes can be finely tuned by varying surface concentration of gold nanoparticles and silver enhancement time. The smallest feature size of the obtained metal mesh patterns is about 700 nm with a thickness of 30-60 nm. The transparent electrodes with the metallic nano-mesh structure exhibit excellent electrical conductivity with a sheet resistance of 70 Ω/sq at a transmittance of 96.2%. Our all water-based solution process can fabricate metal mesh electrodes with high optical transparency, flexibility, and stretchability on plastic substrates.
EM10.10: Poster Session II: Emerging Materials and Techniques
Session Chairs
Friday AM, December 01, 2017
Hynes, Level 1, Hall B
8:00 PM - EM10.10.01
Flexible Non-Volatile Transistor Memory with All-In-One Floating Gate/Tunneling Layer of Transition Metal Dichalcogenides Solution-Processed with Amine-Terminated Polymers
Richard Kim 1 2 , Jinseong Lee 2 , Kang Lib Kim 2 , Suk Man Cho 2 , Michael McConney 1 , Cheolmin Park 2
1 , Wright-Patterson Air Force Research Laboratory, Wpafb, Ohio, United States, 2 Materials Science and Engineering, Yonsei University, Seoul Korea (the Republic of)
Show AbstractNon-volatile memories are widely used in our daily life such as display, cellular phone, and computer and additional tremendous demand is made on the next generation of smart wearable and patchable on skin electronic applications. Currently, the most widely used non-volatile memories are distinguished by various data storage principles such as resistive type, ferroelectric and charge trapping flash memory and these memories have been extensively investigated as candidates for the next generation flexible non-volatile memory market.
Flash type non-volatile organic memories with floating gate have received specific attention due to their outstanding non-destructive readout capabilities and its simple device structure of single transistor. Metal nanoparticles (such as Au, Al, and Ag) and small molecular semiconductors and polymer semiconductors are widely used as a floating gate which is placed between the tunnelling layer and dielectric blocking layer in device structure. Recently, many studies were devoted to further materials such as graphene and transition metal dichalcogenides (TMDs) to achieve excellent and reliable non-volatile memory characteristics. The TMD nanosheets are, however, employed as semiconducting channels in most of the memories, and only a few works address their function as floating gates.
In this work, we developed a fascinating non-volatile floating gate memory with a solution-processed TMDs / amine-terminated polymers as an all-in-one floating gate / tunnelling layer. The successful exfoliation and dispersion of TMD nanosheets begins with segmental Lewis like acid base enthalpic interaction between donated lone pairs of nitrogen atoms in the amine segment of a polymer and the electron accepting metal atoms of TMDs, and the composite films were formed by spin coating process with dispersed solution of TMD nanosheets and amin-terminated polymer. To ensure reliable charge injection, programing, and erasing during memory operation, device performance was systematically examined as a function of the proportion of molybdenum disulfide (MoS2) : amine-terminated polystyrene (PS-NH2) floating gate / tunnelling layers, and under optimized conditions, the devices exhibited a high on/off memory ratio >104 and a long retention time of 7 x 103 s. All-in-one floating gate and tunnelling layers of other TMDs such as molybdenum diselenide (MoSe2) and tungsten disulfide (WS2) are also fabricated with PS-NH2 and the charge trapping and de-trapping behaviour dependent upon gate voltage was observed in both devices with MoSe2 and WS2, similar to one with MoS2. Our device was also fabricated on a flexible polymer substrate, giving rise to excellent memory performance with high memory window, long retention, and write/read cycle endurance, even after 500 bending events under 4 mm bending radius condition.
8:00 PM - EM10.10.02
Solution-Deposited Photovoltaics Using Hydrothermal, Cu2ZnSnS4 Nanocrystal, Absorber Layers
Han Wang 1 , Nate Quitoriano 1 , George Demopoulos 1
1 Mining and Materials Engineering, McGill University, Montreal, Quebec, Canada
Show AbstractThe development of kesterite Cu2ZnSnS4 (CZTS) thin film photovoltaics has the potential to transform the thin film photovoltaic industry, avoiding the toxicity or cost of predecessor materials such as CdTe and CIGS. Solution processing of CZTS thin films are a promising approach to further reduce cost and improve scalability, and has successfully produced high efficiency solar cells. The record cell efficiency recorded with a CZTS absorber layer employs hydrazine solvent during processing, which is problematic for large scale fabrication due to its toxic and volatile nature. Alternative solvents and methodologies are being researched which can avoid the use of hydrazine. Hydrothermal routes have been used to synthesize CZTS nanocrystals, but the use of such nanocrystals to deposit high quality absorber layers is not well explored.
We highlight recent progress our group has made to synthesize high-quality CZTS nanocrystals using a safe, non-toxic hydrothermal route which are characterized using a variety of techniques including XRD and Raman spectroscopy. Parameters of the hydrothermal synthesis such as selection of precursor material, pH, and temperature are addressed. Nanocrystals dispersed in several different solvent media are deposited by spin coating and then annealed in an inert atmosphere. Thin film properties such microstructure, elemental composition, and optical response are analyzed and correlated to the processing parameters.
8:00 PM - EM10.10.04
Doping Copper (I) Iodide with Thiocyanate—Transparent Thin Films and Potential Applications
Ajith DeSilva 1 , J. Harwell 1 , Anne Gaquere-Parker 1 , G.R.A. Kumara 2 , L. W. de Silva 3 , K. Tennakone 3 , Unil Perera 3 , T.M.W.J. Bandara 4
1 , University of West Georgia, Carrollton, Georgia, United States, 2 , Institute of Fundamental Studies, Kandy Sri Lanka, 3 , Georgia State University, Atlanta, Georgia, United States, 4 , Rajarata University of Sri Lanka, Mihintale Sri Lanka
Show AbstractCopper (I) iodide is a well-known high-band gap p- type semiconductor admitting deposition into thin films by many techniques. The hole conduction of CuI depends invariably on stoichiometric excess of iodine introduced during synthesis of the material. Band gap, band off-sets and optical properties depend on level of iodine doping, crystallite size and partitioning of iodine in the bulk and the grain boundaries. As iodine is highly volatile, semiconducting properties of CuI films are affected by sintering and prolonged storage. It is found that thiocyanate is an alternative dopant that greatly stabilize the p-type semiconducting properties of CuI. Thiocyanate doping can be achieved by complete removal of excess iodine and introduction of thiocyanate via suitable precursors at ambient temperature. Electrical and optical properties and potential applications of thiocyanate doped CuI thin films will be discussed.
8:00 PM - EM10.10.05
Wearable Quantum Dot Light Emitting Diodes with Excellent Transparency and Brightness
Dong Chan Kim 1 2 , Moon Kee Choi 1 2 , Jiwoong Yang 1 2 , Woongchan Lee 1 2 , Hyung Joon Shim 1 2 , Jun-Kyul Song 1 2 , Seungki Hong 1 2 , Taeghwan Hyeon 1 2 , Dae-Hyeong Kim 1 2
1 , Institute for Basic Science, Seoul Korea (the Republic of), 2 , Seoul National University, Seoul Korea (the Republic of)
Show AbstractAs the era of internet of things (IoTs) approaches, transparent displays have been highlighted as next generation displays due to their applicability to diverse objects including eyeglasses, windows and mobile devices. To ensure the proper functioning of such ‘see-through’ displays, outstanding transparency and optoelectronic performance are the most critical features to be achieved as a priority. Here, we report quantum dot light emitting diodes (QLEDs) with excellent transparency (90% transmittance at 550nm) and luminance (bottom: ~43,000 cd m–2, top: ~30,000 cd m–2, total: ~73,000 cd m–2 at 9 V) that are superior to other transparent LEDs reported so far. These superb characteristics are accomplished by newly designed electron transport layers (ETLs) and structurally-optimized nanocrystal quantum dots (QDs). The novel ETLs, composed of zinc oxide nanoparticles assembly coated with a few-nanometers-thick alumina layers, perform two important functions; to protect the QD layers from harsh sputtering process, and to optimize the carrier balance by blocking excess electron injection. Moreover, the structure of QDs including their shell thickness and the type of ligands is further optimized to obtain higher optoelectronic performance. The ultrathin/wearable application of transparent QLEDs have 2.7 μm of thickness and high deformability, so that they can easily form conformal integration with various curved objects such as eyeglasses, papers and human skin. Wearable transparent QLEDs provide new opportunities on the field of next generation displays and wearable electronics.
8:00 PM - EM10.10.06
Low Temperature, High Stability of Conductive Copper Electrode for Flexible Applications by Acid-Assisted Laser Sintering Process
Jinhyeong Kwon 1 , Hyunmin Cho 1 , Habeom Lee 1 , Jinwook Jung 1 , Dongkwan Kim 1 , Jaeho Shin 1 , Seung Hwan Ko 1
1 , Seoul National University, Seoul Korea (the Republic of)
Show AbstractCopper is good electrical and thermal conductivity, which compatible with noble metals such as gold and silver. However, the oxidation of copper under an ambient condition is a crucial issue for practical applications. The copper electrode is fabricated on the flexible substrate by acetic acid treatment (AAT), laser sintering process (LSP) and acid-assisted laser sintering process (ALSP). Various analytic measurements such as surface morphology, mechanical bending test, adhesion strength, chemical binding energy and humidity-temperature test are verified to examine the stability of the copper electrode with different post-treatment. In the case of ALSP, the change of the sheet resistance is 1.5% up to 4,000 cycles by mechanical bending test and its adhesion strength to the substrate is better than that of electrodes by AAT and LSP. After a humidity-temperature test, the copper electrode fabricated by the ALSP shows most stable chemical and electrical performances. Finally, the ALSP-processed copper electrode is employed to the flexible applications such as Joule-heater and touch screen panel.
8:00 PM - EM10.10.07
Metal Cluster Based Thin-Film Field-Effect Transistor
Michael Galchenko 1
1 Cluster of Ultrafast Imaging, University of Hamburg, Hamburg Germany
Show AbstractColloidal inorganic nanocrystals have been explored and widely investigated as building blocks for various electronic device applications such as sensors or thin-film transistors. Most beneficial to colloidal materials is the low cost, the possibility of inkjet-printing on flexible substrates and low-temperature solution processing for large area applications. Anyhow, charge transport in thin-films of individual metallic or semiconducting nanocrystals is governed by a large number of tunnel barriers which contradicts the superiority of colloidal 2D materials for the same application.
However, the perceived disadvantage of tunnel barriers combined with the low self-capacitance of each individual metallic nanocrystal resulting in a high Coulomb charging energy can be utilized to realize special device concepts: due to the Coulomb-Blockade regime during charge transport and partial localization of electrons due to tunneling, not only a Coulomb-blockade based field-effect transistor but also a single-electron transistor have been constructed, by solution-processing and physical methods, respectively.
Most investigations on charge transport through individual and 2D arrays of metallic nanocrystals were performed on 2.5 to 15 nm sized nanocrystals. In the recent years, colloidal chemistry experienced a major progress thanks to the work of the group around Prof. J. Rongchao. Since then, nanoclusters in the ultrasmall size regime (1-3 nm), in which the electronic structure of metallic nanocrystals experience a transition from a metallic to a molecule-like character, can be synthesized as stable colloidal suspensions. Furthermore, colloids in this size regime behave surprisingly different compared to their larger counterparts: not only that these nanoclusters can be synthesized with atomic precision but also an excess of organic molecules to stabilize the colloids is unnecessary, what offers the possibility to reach band-like charge transport and increased carrier mobilities in an ordered thin-film.
The presented poster will be focused on a comparative study of charge transport through thin-films of atomically precise metallic nanoclusters, which consist of 24 to 130 atoms, respectively.
8:00 PM - EM10.10.08
Work Function Tuning of Aerosol-Jet Printed Transition Metal Dichalcogenide Thin Films
Chia Wei Liao 1 , Chia Wang 2 , Hong-Tsu Young 2
1 , Academia Sinica, Taipei Taiwan, 2 Department of Mechanical Engineering, National Taiwan University, Taipei Taiwan
Show AbstractTwo-dimensional transition metal dichalcogenides (TMDs) are rapidly emerging and have already shown great potential in electronic applications. However, challenges still remains. Most of TMDs thin films are grown from costly vacuum deposition process. Therefore, for the purpose of achieving a low-cost, vacuum free, as well as solution processable two-dimensional layered materials, we developed a aerosol-jet printable MoS2 and WS2 ink with tunable work function. By employing MoS2 (or WS2) as a covering, we are able to tune work function up to 5.6 eV, which tune the work function of ITO over 0.8 eV. Our results suggest that the potential applications of printable MoS2 (or WS2) ink in optoelectronic (e.g. peroveskite solar cell and organic light emitting diode) would become more viable and promising.
8:00 PM - EM10.10.09
Phototransistors with Epitaxially-Grown AuCN Nanowires on Graphene
Jeongsu Jang 1 , Yangjin Lee 1 , Jun-Yeong Yoon 1 , Jeongheon Choe 1 , Hoon Hahn Yoo 1 , Hu Young Jeong 2 , Kibog Park 1 , Kwanpyo Kim 1
1 Physics, UNIST (Ulsan National Institute of Science Technology), Ulsan Korea (the Republic of), 2 , UCRF (UNIST Central Research Facilities), Ulsan Korea (the Republic of)
Show AbstractThe van der Waals epitaxy of functional materials on graphene provides an interesting and efficient way to manipulate the electrical properties of graphene. Here, we present a facile method to fabricate epitaxially-grown AuCN nanowires on graphene and study the electrical properties of the system under light illumination. The density and size of AuCN nanowires on graphene can be controlled by the AuCN concentration of a solution as well as deposition temperatures. The nanowire morphology and its crystallinity aligned along graphene zigzag directions are studied in detail with transmission electron microscopy, which reveals the effect of kinetic factors during the nanowire formation process. Using AuCN-graphene heterostructures, we fabricate phototransistors and find a large photo-response with responsivity as large as ~104 A/W under UV (3.1 eV) illumination. The effective doping change of graphene is observed under the light illumination. Moreover, photon-energy-dependent measurements show that the phototransistors only response to photons with energy bigger than 2.7 eV, which agrees well with an experimentally observed bandgap of AuCN.
8:00 PM - EM10.10.10
On the Long Term Stability of InAs Nanowires
Kaspar Snashall 1 , Bobour Mirkhaydarov 1 , Philippe Caroff 2 , Maxim Shkunov 1
1 , University of Surrey, Guildford United Kingdom, 2 , Cardiff University, Cardiff United Kingdom
Show AbstractIndium arsenide nanowires are promising alternatives to conventional semiconductors and are of particular interest in solution processable and printed electronics applications. However in order to use these nanowires in real world devices the long atmospheric stability of these nanowires and their devices must be evaluated and methods to prevent decay investigated.
We investigate the long term stability of InAs nanowires field effect transistors (FETs) in ambient atmosphere and compare methods for encapsulation and protection of these semiconductors. InAs nanowires are grown by metal organic chemical vapour deposition. Back gated field effect transistors FETs are fabricated and are used to assess the long term stability of the nanowires. Both atomic layer deposited alumina and parylene encapsulation are investigated as possible ways of protecting devices. Tests in nitrogen, dry air and ambient atmosphere are performed and the effects of humidity, temperature and light conditions are investigated. Transistors are measured over a number of weeks to assess the variation of the main FET parameters including on-current, threshold voltage, subthreshold swing, mobility and on/off ratio. Voltage bias stress tests are also performed to assess device stability.
8:00 PM - EM10.10.11
Graphene Inks for 3D Printing Using Capillary Suspensions
Hui Ding 1 , Brian Derby 1 , Suelen Barg 1
1 , University of Manchester, Manchester United Kingdom
Show Abstract2D materials have applications as functional materials exploiting their 2D geometry and unique electronic properties or their extremely high specific surface area for electrodes and sensors. For large area applications suitable stable inks are needed for their use with printing methods. 3D printing of 2D aerogels is of particular interest for energy storage with printable batteries and supercapacitors. However, aerogels require complex processing techniques such as gel casting and freeze drying to achieve their desired structure. Here we describe an alternative ink design method to allow 3D printing and air drying of highly porous graphene based materials.
There are a number of different ways by which printing methods can be used to create 3D structures, here we will describe inks developed for dispensing through small diameter nozzles to “write” a structure in the form of a series of filaments. This includes a family of related methods called variously: robocasting, directed ink writing and fused deposition modelling. It has become the default technique termed 3D printing by the “maker” community. Inks used for these methods require a specific set of rheological properties that allows the ink to easily flow when extruded through the nozzle, yet maintain the desired shape after printing. Hence there must be a very large change in the viscosity of the fluid as it leaves the printer. This can be achieved through a number on methods including: phase change (extruding the ink through a heated nozzle onto a cold surface), polymerisation (using an external trigger e.g. photoinitiated polymerisation), or by using a fluid with extreme non-Newtonian behaviour that shows extreme shear thinning or a Bingham yield behaviour.
Here we describe a new concept for ink design using the principles of capillary suspensions [1]. In a capillary suspension two immiscible fluids are used one of which has a strong affinity for the particles in suspension. This produces a structure similar to a Pickering emulsion with chains of particles surrounding small fluid domains. Such fluid structures have very high viscosity at low shear rates but this rapidly reduces if the shear disrupts the capillary emulsion structure. Following work using this method to process graphite suspensions [2], we demonstrate that relatively small additions of octanol (around 2% by volume) to aqueous graphene inks lead to the viscosity increasing by a factor of 100 or greater at low shear rates but converges to that of the original suspension at high shear rates. These inks have been used to print simple 3D structures using a nozzle extrusion system. The resulting deposits after drying show high specific surface areas, high electrical conductivity and linear shrinkage in the range 10 -50% during drying.
[1] E. Koos and N. Willenbacher, Science 2011, 331(6019) 897–900.
[2] B. Bitsch et al. J. Power Sources 2016, 328 114-123.
8:00 PM - EM10.10.12
Silver Nanowire Networks as Transparent Electrodes for Organic Photovoltaics and Light Emitting Diodes
Ece Alpugan 1 , Gonul Hizalan 2 , Gorkem Gunbas 2 , Ali Cirpan 2 , Levent Toppare 2 , Husnu Unalan 1
1 Metallurgical and Materials Engineering, METU, Ankara Turkey, 2 Chemistry, METU, Ankara Turkey
Show AbstractTransparent electrodes are widely used in optoelectronics, touchscreens, organic photovoltaics (OPVs) and organic light emitting diodes (OLEDs). High transparency, conductivity and physical stability are required properties for those applications. Indium tin oxide (ITO) is the mostly utilized and commercially available transparent electrode material due to its long-term stability and ideal optoelectronic properties. ITO suffers from limited structural flexibility and its relatively high cost, while silver (Ag) nanowire networks are proposed as a highly promising alternative material to ITO thin films. In this work, ITO thin films are replaced with Ag nanowire networks. Spray coated Ag nanowires networks are used as anodes in OPV and OLEDs. Moreover, for this work, a novel polymer (P1) poly((9,9-dioctylfluorene)-2,7-diyl-(4,7-bis(thien-2-yl)2-dodecyl-benzo[1,2,3] triazole) was synthesized with benzene end capper in order to be used as the active layer in both devices. Control OPV devices were constructed with a structure of glass/ITO/PEDOT:PSS/P1/LiF/Al, where a photovoltaic conversion efficiency (PCE) of 4.10 % was obtained. Afterwards, ITO was replaced with Ag nanowire network electrodes and a PCE of 0.50 % is measured. For OLEDs, on the other hand, devices were fabricated within glass/Ag nanowire network/PEDOT:PSS /P1-PCBM/LiF/Al structure and it is found that these devices have lower turn on voltage (2.75 V) compared to those fabricated on ITO (3V).
This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) under Grant No: 115M036.
8:00 PM - EM10.10.13
Hybrid Inorganic Ambipolar Transistors with Dye Functionalization for Efficient and Fast Photo-Sensing Application
Wentao Huang 1 , Yen-Hung Lin 1 , Thomas Anthopoulos 1 2
1 , Imperial College London, London United Kingdom, 2 , King Abdullah University of Science and Technology (KAUST) , Thuwal Saudi Arabia
Show AbstractPrintable photodetector technologies have been attracting increasing attention due to their potential for cost-effective, low-temperature and large-area manufacturing of devices for image sensing, optical communication and energy harvesting applications. Solution processable metal oxides represent an attractive family of semiconducting materials for use in high carrier mobility thin-film transistors and integrated circuits. When comes down to photodetector applications, however, their wide optical bandgap limits their application in ultraviolet (UV) photodetectors. Recently, studies on oxide-based phototransistors (PTs) employing an additional light-absorbing layer such as low-dimensional nanomaterial, organic polymer, or an organic dye or organometal halide perovskite, have been reported. In this way, the photoresponse of the PTs can be significantly improved in the visible range of the electromagnetic spectrum. Despite the promising work, however, oxide-based PTs are known to exhibit unstable operating characteristics especially under continuous illumination, which leads to persistent photoconductivity and limits the operating speed of the PTs.
Here we report the development of a novel p-n heterostructure hybrid inorganic transistor based on two solution-processed oxide semiconductors, namely indium oxide (In2O3) and copper thiocyanate (CuSCN). The presence of the p-n (In2O3/CuSCN) junction enables ambipolar transistor operation, while maintaining a high optical transparency (transmission>90% across the visible spectrum (400-700nm). The ability of visible light detection is then enabled through the incorporation of a green light-absorbing organic dye in the vicinity of the heterostructure during growth. The trilayer In2O3/dye/CuSCN channel PTs show a remarkably enhanced photoresponse to green photons as compared to the control In2O3/CuSCN-based devices. More interestingly, we find that the devices can be operated at high speed with a response time of ~1 ms. The latter is attributed to the synergistic effects of high hole/electron mobility across the In2O3/dye/CuSCN channel and the efficient photo-generation of free carriers upon light-absorption by the dye. Minimization of the surface-oxygen-vacancy-related photoconductivity due to the multilayer nature of the photo-active channel is also believed to play an important role and will be analysed in detail. The hybrid phototransistor developed here is compatible with other light absorbing materials, offering a universal approach towards a wavelength-selective or panchromatic photosensor technology.
8:00 PM - EM10.10.15
Solution Processed Thin Films of Transition Metal Dichalcogenides for Device Applications
Joe Neilson 1 , Brian Derby 1
1 , The University of Manchester, Manchester United Kingdom
Show AbstractSince the discovery of graphene in 2004, there has been an explosion of interest in the field of 2D materials. Semiconducting 2D materials, such as the Transition Metal Dichalcogenides (TMDs), which have attractive electrical properties, have been widely explored for use in the fabrication of devices such as; field-effect transistors (FETs), sensors, and light emission devices. As with organic semiconductors, TMDs can be handled in solution, which may allow for the formulation of an ink for use in high throughput and low cost printed electronic devices with greater mobilities than current organic printed devices.
Focusing specifically on FETs, devices manufactured around single mechanically exfoliated or chemical vapour deposition (CVD) grown flakes with mobilities greater than 700 cm2.V-1.s-1 have been widely reported. However, current literature demonstrates that working solution processed TMD FETs are largely non-existent. The reason for the observed shortcomings in such devices is unknown, but possible reasons can be broadly narrowed down to cleanliness of the flakes, and poor flake-flake contacts within a film of solution processed TMD material.
Here, we will present current experimental efforts designed to improve and understand the possible failure modes of, solution processed TMD devices. This presentation can be split into two parts. Firstly, we will describe new methods for thin film assembly from solution processed few layer 2D materials such as assembly via a Pickering emulsion intermediate, Langmuir-Blodgett assembly, and capillary force self-assembly: a versatile technique which may also act to passivate the surface of the film or act as an electrolytic gate material for the manufactured device. Finally, we will display experimental efforts which further our understanding of the parameters which improve or reduce the performance of working, mechanically exfoliated, FETs such as; passivation of the surface of the channel material, and stressing working devices in order to determine the failure modes of such devices.
Revealed herein are example devices, including FETs and photo detectors, manufactured around thin films of various simple, low cost, and highly scalable assembly methods, with discussion on the most effective strategies. This work also provides insights into the manufacturability of solution processed 2D FETs by elucidating and resolving some of the failure modes associated with solution processing methods, and is a step towards the design of a robust and simple manufacture technique for FETs made from solutions of 2D TMD material.
8:00 PM - EM10.10.16
Low-Temperature and In-Place Additive Printing of Carbon Nanotube Transistors Enabled by Silver Nanowire Contacts
Jorge Cardenas 1 , Matthew Cattenacci 1 , Benjamin Wiley 1 , Aaron Franklin 1
1 , Duke University, Durham, North Carolina, United States
Show AbstractThe need for ubiquitous and flexible electronics to facilitate the rapidly growing internet-of-things (IoT) has driven the advancement of low-cost and high-throughput fabrication. Specifically, printed electronics has shown promise for low-temperature fabrication with the versatility of integrating electronics in an additive fashion, onto virtually any surface. What remains missing from the field of additively printed electronics is the ability to print key functional layers/inks sequentially without requiring other treatments outside of the printer (e.g., baking, spin-coating, patterning). Such processing, external from a printer, adds considerable time to the fabrication process, compromising one of the key benefits of a printing approach: throughput. In this work, we demonstrate a low-temperature and completely in-place aerosol jet printing approach for fabricating carbon nanotube thin-film transistors (CNT-TFTs) with ON/OFF current ratios as high as 105 and ON-currents as high as 90 µA/mm. These devices are entirely printed, from first step to last, without removal of the substrate from the printer; hence, no external baking, coating, or other treatments. As an alternative to standard silver nanoparticle contacts in CNT-TFTs, we used an ink consisting of high aspect ratio silver nanowires that achieves both high conductivities and low contact resistance without the need for high-temperature sintering. With the platen (supporting the substrate) held at 80°C or less, the CNT-TFT is printed onto a doped-Si/SiO2 substrate by first printing semiconducting CNTs into a thin film for the transistor channel. Next, an in-place rinse with toluene is performed followed by printing Ag nanowires to form the source and drain contacts. In addition to our demonstration of the in-place printing of CNT-TFTs, this work presents the first use of aerosol jet printed silver nanowire thin films, including the ink formulation and optimization of printing parameters for highest conductivity and compatibility with an Optomec AJ300 aerosol jet printer and printed CNT thin films. In summary, this work presents the aerosol jet printing of silver nanowire electrodes in CNT-TFTs that enable low-temperature and in-place fabrication that is highly suitable for the low-cost and high-throughput manufacture of electronic devices.
8:00 PM - EM10.10.17
Colloidal Synthesis and Integration of Uniform-Sized Molybdenum Disulfide Nanosheets for Wafer-Scale Nonvolatile Memory
Sue In Chae 1 , Taeghwan Hyeon 1
1 , Seoul National University, Seoul Korea (the Republic of)
Show AbstractTwo-dimensional materials, ranging from graphene to transition metal dichalcogenides, have attracted enormous attention for next generation electronics and optoelectronics, including flexible device technologies, owing to their unique band structures, high mobility, and atomic scale thickness. Numerous discoveries based on molybdenum disulphide (MoS2), as a representative two-dimensional inorganic material, have been reported in physics and chemistry area. In the early 2010s, excellent performances of devices made of exfoliated MoS2 from its bulk have been exhibited, although most results are based on individual devices rather than large-scale device arrays. Recent advance in the large-area synthesis of MoS2 by means of chemical vapor deposition (CVD) suggests the feasibility of fabricating wafer-scale device arrays. However, the high cost of the vapor-phase synthesis in an ultrahigh-vacuum system is a critical issue. The assembly of exfoliated MoS2 nanosheets via solution-process may solve these issues. However, the non-uniformity witnessed in large-area device arrays, which is inevitable by the intrinsic polydispersity of the exfoliated MoS2, remains as a serious problem. Therefore, a breakthrough in the uniform synthesis and integration of high quality MoS2 through colloidal nanochemistry is highly desirous.
In this study, we present the colloidal synthesis of uniform-sized MoS2 nanosheets in large-scale and integrated them for a wafer-scale resistance random access memory (RRAM) array on a flexible substrate. The size and thickness of the synthesized MoS2 nanosheets are highly uniform, in comparison with exfoliated MoS2. A uniform MoS2 film over a 4-inch wafer is produced by spray coating of the well-dispersed nanosheets. The memory performance of the device based on the synthesized MoS2 nanosheets surpasses that of a control device made of exfoliated MoS2, for example, the extremely high on/off ratio of the RRAM. In addition, the ultrathin characteristics of the assembled MoS2 nanosheets enables the fabrication of flexible devices. Finally, the wafer-scale uniformity of the MoS2 RRAM array is employed in a system-level demonstration such that pressure sensors and quantum dot light-emitting diodes (QLEDs) are integrated with it to accomplish a flexible data storage and display system.
References
D. Son, S.I. Chae, M. Kim, M.K. Choi, J. Yang, K. Park, V. S. Kale, J.H. Koo, C. Choi, T. Hyeon*, D.-H. Kim*, Adv. Mater. 28, 9326 (2016).
8:00 PM - EM10.10.18
Highly Efficient Flexible Organic Solar Cells Using Cold Isostatic-Pressured Silver Nanowire Electrodes
Ji Hoon Seo 1 , Inchan Hwang 1 , Han-Don Um 1 , Kangmin Lee 1 , Jeonghwan Park 1 , Kwanyong Seo 1
1 Energy Engineering, Ulsan National Institute of Science and Technology, Ulsan Korea (the Republic of)
Show AbstractFlexible organic photovoltaic devices are one of the most promising energy conversion devices in the solar energy industry. To fabricate high-efficiency flexible organic solar cells (FOSCs), it is essential to develop flexible and transparent conducting electrodes. Generally, organic photovoltaics are fabricated using indium–tin–oxide (ITO) electrodes that can easily be broken by an external bending force. An AgNW/PET electrode has been devised for replacing the ITO electrode in FOSCs. However, AgNW/PET electrodes are treated by a thermal process (>100 °C) that can generate internal short-circuiting, as it improves the electrical property of AgNW films. In this study, we fabricated highly conductive AgNW electrodes using cold isostatic pressing (CIP) process that were used to develop highly efficient and reproducible flexible organic solar cells. This method increases the conductivity of the AgNW electrodes, which enables the fabrication of high-efficiency inverted FOSCs that have a power conversion efficiency of 8.75% with no short-circuiting. In addition, these FOSCs not only have excellent bending properties, but also achieves 100% manufacturing yield of FOSCs.
8:00 PM - EM10.10.19
Graphene/Ag-Nanowire Composite Conductive Microfibers with Humidity Sensing Ability
Yang Woo Lee 1 , Bongjun Yeom 2 , Ju-Hee So 3 , Hyung-Jun Koo 1
1 Department of Chemical and Biomolecular Engineering, Seoul National University of Science and Technology, Seoul Korea (the Republic of), 2 Department of Chemical Engineering, Myongji University, Yongin Korea (the Republic of), 3 Research Institute of Industrial Technology Convergence, Korea Institute of Industrial Technology, Ansan Korea (the Republic of)
Show AbstractShaping of conductive materials into 1-D geometry, such as wire or fiber, could make materials more flexible and processable. Due to such a potential advantage, 1-D conducting materials can find many applications including wearable electronic/energy devices and smart textiles. In this study, we fabricate highly flexible conducting microfibers by facile and versatile extrusion/drying process of agarose gel filaments with hydrophilic conducting fillers. Graphene oxides and silver nanowires are embedded in the microfibers as the hydrophilic fillers to endow electrical conductivity to the insulating agarose microfiber. TEM images of the microtomed-composite fibers confirm that two hydrophilic fillers are well distributed without significant aggregation in the agarose fiber matrix. The synergistic effect of the conductive fillers of graphene oxides reduced by hydrazine and silver nanowires not only improves the electrical conductivity, but also allows the balanced mechanical property of the composite microfiber. Humidity sensing ability of the composite microfiber is demonstrated based on swelling-deswelling behavior of the agarose fiber.
8:00 PM - EM10.10.20
Percolation-Controlled Metal/Polyelectrolyte Complexed Films for Multifunctional Coating
Min Jun Oh 1 , Pil Jin Yoo 1
1 , SungKyunKwan University, Suwon Korea (the Republic of)
Show AbstractThe use of solution-processable electrically conducting flms is imperative for realizing next-generation flexible and wearable devices in a large-scale and economically viable way. However, the conventional approach of simply complexing metallic nanoparticles with a polymeric medium leads to a tradeoff between electrical conductivity and material properties. To address this issue, in this study, a novel strategy is presented for fabricating all-solution-processable conducting flms by means of metal/polyelectrolyte complexation to achieve controlled electrical percolation; this simultaneously imparts superior electrical conductivity and good mechanical properties. A polymeric matrix comprised of polyelectrolyte multilayers is frst formed using layer-by-layer assembly, and then Ag nanoparticles are gradually synthesized and gradationally distributed inside the polymeric matrix by means of a subsequent procedure of repeated cationic exchange and reduction. During this process, electrical percolation between Ag nanoparticles and networking of electrical pathways is facilitated in the surface region of the complexed flm, providing outstanding electrical conductivity only one order of magnitude less than that of metallic Ag. At the same time, the polymer-rich underlying region imparts strong, yet compliant, binding characteristics to the upper Ag-containing conducting region while allowing highly flexible mechanical deformations of bending and folding, which consequently makes the system outperform existing materials.
8:00 PM - EM10.10.21
Synthesis of InxGa1-xAs/ZnSe Quantum Dots by Colloidal Method
Soo-wung Park 1 , HaeUn Seo 1 , Joong-Pil Park 1 , Sang-Wook Kim 1
1 , Ajou University, Suwon-si Korea (the Republic of)
Show AbstractSoo-Wung Park1, Hae-Un Seo2,Joong-Pil Park2† and Sang-Wook Kim*†
†Ajou University ;164, World cup-ro, Yeongtong-gu, Suwon-si, Gyenggi-do, Korea
Semiconductor nanocrystals(QDs) grown using chemical synthetic methods have attracted attention due to their advantages and convenience. GaAs is an important semiconductor material because of its use in solar cells and optoelectronics. But they are hard to obtain by chemical synthetic method. Therefore, GaAs QDs have been generally fabricated by physical method such as chemical vapor deposition(CVD). Herein, we report GaAs/ZnSe and InxGa1-xAs/ZnSe core/shell QDs synthesized by colloidal method. We add acetylacetonate complexs of indium and gallium as cationic precursors into common fatty acid-ODE system. PL wavelength was controlled by the In/Ga ratio and tuned from orange to deep red.
8:00 PM - EM10.10.23
Effect of the Substitution of Se for S in GLS Glasses—Ab Initio Analysis
Kazimierz Plucinski 1
1 , Military University of Technology, Warsaw Poland
Show Abstract
Glasses based on Ga2S3-La2S3 with Ga2Se3 added right up till there is total substitution of Ga2S3 for Ga2Se3, are analyzed. The following issues are analyzed: effect of replacement of S for Se on the bandgap and transmission window, especially on LWIR (long-wave infrared transmission); effect of the substitution of Se for S on the infrared cutoff wavelength; influence of the substitution of Se for S on the energy of molecular vibration and wavelength of the multiphonon edge; possibility to tailor refractive index with appropriate content of Se. The following calculation methods are applied: RMC (Reverse Monte Carlo), HRMC (Hybrid Reverse Monte Carlo), DFT MD (Density Functional Theory and Car-Parinello Molecular Dynamics).
It is shown, that ab initio analysis helps to choose appropriate content of Se, thereby expands the possibilities of application of such modified GLS glasses in photonics, like graded index lenses or optical fibers.
8:00 PM - EM10.10.25
Improved Accuracy in Quantification of Analyte through Dual Modality Multi-Site Sensing
Sakshi Sardar 1 , Laura Fabris 1 , Mehdi Javanmard 1
1 , Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States
Show Abstract
We introduce a technique, which results in 10X improvement in precision of surface enhanced Raman spectroscopy measurements, by combining dual Raman/Electrochemical measurements, at multiple sites with induced diversity through customized nanoparticle based ink. Sensors that can give prompt, specific and quantitative response are highly desirable in detection techniques. In addition, minimal sample preparation time, easy to use machinery, and lower cost of production could enable economic and easily deployable solutions.
SERS is one of the most highly selective and sensitive techniques to detect molecular species. Even though it is an excellent tool for qualitative measurements, quantitative measurements can have variability from one site to another on the same substrate, owing to clustering of particles and orientation of the analyte. This issue poses a great challenge for quantifying the SERS signal on inorganic films. In the present proof of concept study, we used nanoparticle based ink for printing films on the sensors. The ink is customized to induce variability on the substrate. The variability is then processed through electrochemical measurements, which in turn are correlated with the enhanced Raman signal from the analyte. Modulation of the Raman signal through customization of the ink resulted in higher fidelity data extraction. Integration of Raman signal with the electrochemical measurements provided higher precision for analyte detection.
Sensors were designed using the screen printed electrodes (SPE). Working electrode of the SPEs was functionalized with different concentrations of gold nanoparticles using cysteamine as the tether. Coulometric measurements were then performed on the SPEs for surface area estimation. 4-aminothiophenol (4-ATP) was chosen as the analyte of interest and was drop casted on the nanoparticle-functionalized SPEs. Raman measurements were then performed on these SPEs.
The coulometric response for the electrodes was proportional to the nanoparticle concentration deposited on the working electrodes. After 4-aminothiophenol functionalization on the working electrode, Raman maps were collected on at least 1500 points for each SPE with different concentration of nanoparticles. The mean intensity value (after baseline subtraction) of the peak centered at 1770 cm-1 was chosen for analysis. The mean Raman intensity increased with nanoparticle concentration. The peak intensity lies within a narrow range at each nanoparticle concentration, opening up the opportunity to using this approach for quantitative analyte detection via SERS. The detection accuracy can be improved by carrying out the measurements on SPEs with different nanoparticle concentration using the fitted curve. Adjusted R-square value for the fit is 0.79957. The single-site measurement yields a variance of 0.15, whereas the multi-site measurement yields a variance of 0.0177, almost a 10X improvement in measurement precision.
8:00 PM - EM10.10.26
Development, Printing and Post Processing of Long-Term Stable Inorganic Inks for Printed Electronics
Julia Gebauer 1 , Viktor Mackert 1 , Markus Winterer 1
1 Nanoparticle Process Technology, University of Duisburg-Essen, Duisburg, North Rhine-Westphalia, Germany
Show AbstractThere is a growing interest in science and industry for printed electronics. Printed electronics allow the production of larger quantities of electronic components at low cost [1]. Even though organic semiconductors are already widely used for printed components, partially inorganic materials are advantageous due to their high durability and superior device performance. On the other hand, a common drawback of inorganic semiconductors is the high processing temperature, which strongly limits the use of low-cost or flexible substrates. In order to overcome this problem we apply resonant UV-laser sintering as thermal post treatment method [2].
In this work we present the formulation, printing and processing of newly developed inks based on ethylene glycol as dispersion media. Different metal oxides (ZnO, TiO2, CuO, SnO2 and In2O3) were stabilized and the colloidal stability was evaluated by a combination of DLVO simulations and DLS measurements. The inks show narrow size distributions, excellent long-term stability and adjustable rheological properties that make them ideally suited for printed electronics.
The newly developed ink formulations are stabilized using the same dispersion media. Therefore, they allow mixing of different nanoparticles in the same ink. We show that this enables completely new production routes to designing complex oxide materials like Zn2SnO4 (ZTO) through reactive laser sintering. Resonant UV-laser sintering of metal oxide structures is advantageous, due to short processing time, efficient energy deposition and localized heat load which makes it ideal for printing on flexible substrates [3].
[1] A. S. G. Khalil, S. Hartner, M. Ali, H. Wiggers, M. Winterer, J. Nanosci. Nanotechnol. 11, 10839-10843 (2011).
[2] A. Sandmann, C. Notthoff, M. Winterer, J. Appl. Phys. 113, 0044310 (2013).
[3] S. K. Garlapati, J. S. Gebauer, S. Dehm, M. Bruns, M. Winterer, H. Hahn, S. Dasgupta, Adv. Electron. Mater. accepted (2017).
8:00 PM - EM10.10.27
Statistical Model for Coupled Resistance and Transmission in Conductive Nanowire Networks
William Sampson 1 , Brian Derby 1 , Catherine Ainsworth 2
1 , University of Manchester, Manchester United Kingdom, 2 , SmartKem Ltd, Manchester United Kingdom
Show AbstractAs industrial and societal demand for transparent conducting materials used in displays, solar cells, etc., increases, there is a considerable focus on the identification of suitable material systems to replace the current material of choice, indium-tin oxide, which is a finite and rapidly depleting resource. Among the candidate systems to replace doped metal oxides are metal nanowire networks formed by spray coating, dipping, etc., from a low concentration aqueous suspension. The resultant films consist of sparse random arrays of metal nanowires with conductivity and optical transmission determined by the number of nanowires deposited per unit area and nanowire dimensions.
A large body of experimental work reported in the literature shows that for arrays of nanowires with given dimensions, the relationship between the two materials properties of primary interest, sheet resistance and optical transparency, is nonlinear, one-to-one and closely coupled. Although various Figures of Merit have been proposed, the precise interdependence of sheet resistance and optical transparency is not known.
Here we present a model for sheet resistance and optical transparency of random nanowire networks. Our analysis considers the statistical
geometry of Poisson process of nanowires to determine the number of junctions between nanowires per unit area. By taking account of the relative magnitudes of resistance of the nanowires and the junctions between them at points of contact, we obtain the resistance of a conducting path of a network at the percolation threshold. From this, we obtain the resistance of the full network as an assembly of parallel conducting paths. Optical transmission is obtained as a simple function of the Poisson probability of network coverage.
Our theoretical treatment provides a simple analytic expression providing the sheet resistance as a function of nanowire aspect ratio, network transmittance and the resistance of nanowires and junctions. The analysis reveals why transmission is independent of nanowire length, how resistance depends on nanowire length and why theoretical treatments that assume all resistance to arise from junctions between nanowires can be made to agree with data arising from systems with knon and finite resistance withing nanaowires. Agreement with experimental and simulation data from the literature is excellent. We close our treatment with discussion of the infleuence of a distribution of lengths of nanowires on sheet resistance and the inherent structural nonunifomity of networks and its implications for local resistance and transmision,
8:00 PM - EM10.10.28
Electrochemical Synthesis of Flower-Like Ag Nanocrystals for Non-Enzymatic Glucose Detection
Jianan Chen 1
1 , Department of Mechanical Engineering The University of Hong Kong, Hong Kong Hong Kong
Show AbstractThis work presents a new electrochemical approach to convert a thin metal film into metal nanocrystals (NCs) with a wide range of surface-to-volume ratios, in shapes such as flower-like, nanorods, dendrites, decahedrons, and icosahedrons. This cyclic scanning electrodeposition method is demonstrated by stripping off a bulk Ag thin film in a neutral electrolyte to produce a temporary high Ag+ concentration near the Ni electrode surface, and then re-electroplating the Ag via different potential waveforms under an abrupt decrease in the Ag+ concentration. This method can be readily extended to other metals or bi-metallic systems. The synthesized three-dimensional flower-like Ag NCs are chosen to demonstrate the enhanced catalytic activity for electro-oxidation of glucose with a wide linear range (0.1μM-1mM), fast response time (less than 2s), low detection limit of 0.1μM (S/N=3) and high sensitivity in the amperometric test. The Ag NCs/Ni electrode shows a high selectivity of glucose detection at a wide range of operating potential because the negatively charged NiO layer can repel the negatively charged anti-interference UA and AA molecules. This finding is expected to lead to a progress in the practical development of Electrochemical Non-enzymatic Glucose Sensors.
8:00 PM - EM10.10.29
Flexible Metal Network Based Transparent Electrodes for Optoelectronic Devices
Bin Hu 1 , Yunsheng Fang 1 , Jun Zhou 1
1 , Huazhong University of Science and Technology, Wuhan China
Show AbstractNanowire networks have emerged as a new type of transparent conductor and have attracted wide attention because of their all solution-based process manufacturing and excellent flexibility, aiming to replace rigid and brittle metal oxides for flexible optoelectronic device applications. However, the completely different mechanism of achieving high transparent and conductive determines that we need find a different optimal strategy to satisfy various applications requirement. For example, the network percolation characteristics make its fine-pattern performance degrade notably, which is a critical issue for practical application in high-resolution devices, while for the thin film solar cells, not only highly transparency and conductivity is needed, higher haze and carrier collection efficiency are also important. The design of nanowire materials and their network geometry thus play important roles.
Motivated by these challenges, we design a aligned architecture, by which the ordered silver nanowires network exhibits improved electro-optical performance compared to the random counterpart, and the fine pattern conductivity increases dramatically as well, which is helpful to the performance of high resolutions quantum dot light-emitting diodes (QLEDs) when using it as bottom electrode. In addition, we also design a hazy network but possessed high transmittance and conductivity using overlooked thick silver nanowires as raw materials, and the semitransparent perovskite solar cell using it as top electrode exhibits the power conversion efficiency up to 16.03% and 11.12% when irradiated from bottom side and top side, respectively.
8:00 PM - EM10.10.30
Cs+ Incorporation Into CH3NH3PbI3 Perovskite—Substitution Limit and Stability Enhancement
Laxman Gouda 1 , Ralf Niemann 2 , Jiangang Hu 1 , Shay Tirosh 1 , Ronen Gottesman 1 , Petra Cameron 2 , Arie Zaban 1
1 , Bar-Ilan University, Ramat-Gan Israel, 2 Chemistry, Bath University, Bath United Kingdom
Show AbstractRecent progress in the field of hybrid organic-inorganic perovskites ABX3 for photovoltaics has given cells with certified efficiencies of 22.1 % solar to electric power, mainly based upon the hybrid inorganic-organic methylammonium lead iodide perovskite MAPbI3 (MA+ = CH3NH+3). Up to now, one of the biggest drawbacks is poor stability towards humidity and temperature. A substitution of the organic MA+ with inorganic Cs+ yields the extremely stable structure CsPbI3, which however forms a yellow δ-phase at room-temperature that is not photoactive. In this study we have systematically explored the mixed cation perovskite CsxMA1-xPbI3. We exchanged the A- site cation by dipping MAPbI3 films into a CsI solution, thereby incrementally replacing the MA+ in a time-resolved dipping process and analysed the resulting thin-films with UV-Vis, XRD, EDAX, SEM and optical depth-analysis in a high-throughput fashion. Additional in-situ UV-Vis and XRD measurements allowed us to look at the kinetics of the formation process. The results showed a discontinuity during the conversion. Firstly, small amounts of Cs+ are incorporated into the structure. After a few minutes, the Cs content approaches a limit and the material segregates into smaller grains of δ-CsPbI3, indicating a broad miscibility gap. We compared this cation exchange to a one-step crystallisation approach and found the same effect of phase segregation, which shows that the miscibility gap is an intrinsic feature rather than a kinetic effect. Optical and structural properties changed continuously for small Cs incorporations. Larger amounts of Cs result in phase segregation. We estimate the miscibility gap of CsxMA1-xPbI3 to start at a Cs ratio x = 0.13, based on combined measurements of EDAX, UV-Vis and XRD. The photovoltaic performance of the mixed cation perovskite shows a large increase in device stability from days to weeks. The initial efficiency of mixed CsxMA1-xPbI3 devices decreases slightly, which is compensated by stability after a few days.
8:00 PM - EM10.10.31
Low Power Operated Highly Responsive UV Photodetector Based on Chemically Doped Bilayer Graphene and Zinc Sulfide Quantum Dots
Tej Limbu 1 , Daysi Diaz 2 , Frank Mendoza 1 , Vladimir Makarov 1 , Brad Weiner 2 , Gerardo Morell 1
1 Physics, University of Puerto Rico, Rio Piedras, San Juan, Puerto Rico, United States, 2 Chemistry, University of Puerto Rico, Río Piedras, San Juan, Puerto Rico, United States
Show AbstractGraphene-quantum dot hybrid structure based photodetectors have drawn the attention of scientific community due to their remarkable performance. However, most of the previously reported photodetectors require high gate voltage for high responsivity which makes the device unsuitable for practical applications. Here, we report fast and highly responsive ultraviolet (UV) phototransistor made from strongly p-doped bilayer graphene and zinc sulfide (ZnS) quantum dots, which perform excellently at zero gate voltage and a small bias voltage of 1 V. Under 254 nm UV light and 0.2 mW/cm2 of illumination, the device shows a responsivity as high as 7.6×105 A/W and photoconductive gain of about 107 electrons per photon. Our results pave a new way of designing photodetectors that perform excellently with a minimal power consumption.
8:00 PM - EM10.10.32
Development of Self-Cleaning Reflective Electrodynamic Screen and Its Applications to CSP Mirrors for Solar Thermal Energy Generation
Annie Rabi Bernard 1 , Malay Mazumder 1 , Mark Horenstein 1 , Ryan Eriksen 1
1 , Boston University, Brookline, Massachusetts, United States
Show Abstract
We report the experiments performed and methods employed to increase the reflectivity of the electrodes of an electrodynamic screen (EDS), a self-cleaning technology that can be retrofitted onto CSP installations to remove dust buildup. Significant research and progress have been reported with respect to transparent conducting electrode material, whereas reflecting electrode materials have not been considerably investigated. Reflecting EDS have silver paste ink as an electrode material, screen printed on thin borosilicate glass films. To increase the productivity of CSP plants, the specular reflectivity (SR) of the electrodes of the EDS must be maximal. Effectively, the electrodes must reflect on either sides to ensure maximum emission of the incident sun rays. The electrode surface on the bottom side results to be highly reflective due to the smooth surface obtained when pressed onto the glass film while screen printing. The upper surface becomes rugged after the curing process and hence has to be leveled. Our experiments with curing temperatures and atmospheric conditions post screen printing have proven to produce smoother surfaces as when compared to commonly practiced oven curing techniques. Electroplating silver on the top surface of these smooth electrodes will result in improved SR. Data obtained from mirror surfaces produced in lab, whose ink was developed using silver nitrate as the active agent, yielded elevated SR data points. This ink can be administered atop the existing electrodes by screen printing with sparse mesh screens or spray coated using stencils. Data from surfaces with reactive silver ink produced by a modified Tollen’s process, using silver acetate as the active agent, deliver desirable SR data but show poor adhesion to the EDS’s glass surface. This is resolved by addressing the adhesion property of the ink to glass by treating the glass surface with ROI etching and adding binder agents to the developed ink. EDS films produced via Gravure Offset Printing (GOP) as transition from lab to roll-to-roll printing provides convenient means for the inclusion of reflective coatings. The EDS produced by photolithography, using highly reflective chrome as the electrode material, achieved the desired specular reflectivity. High reflectance of silver can also be extended by depositing it as a thin layer atop aluminum and sandwiching the structure between two thin layers of NiCrNx, thus protecting it from tarnishing. This is done using photolithography and spin coating or sputtering methods. Success of the aforementioned experiments will enable reflective EDS to output SR > 90% and specular reflection restoration (SRR) > 95%. This will aid in enhancing the functionality of CSP installations that currently face obstruction of sunlight due to the dust layer buildup which decreases the power plants maximum efficiency.
8:00 PM - EM10.10.33
Inkjet Printing of Nanoparticle-Based and Reactive Silver Inks for Electronic Applications on Temperature Sensitive Substrates
Anita Fuchsbauer 1 , Helene Ausserhuber 1 , Florian Durst 1 , Vanessa Tober 1 , Julia Kastner 1 , Michael Muehlberger 1
1 , Profactor GmbH, Steyr-Gleink Austria
Show AbstractInkjet printing allows the contact free deposition of different types of materials at a well-defined position on various types of substrates and can thus be used to create micro- and macrostructures. Inkjet printing is by far not limited to graphical paper printing [1] any more, but is used in printed electronics [2], [3], display printing [4] and other areas. For inkjet printing of functional devices often multilayer structures of different materials are necessary (e.g. intercrossing of electrically conductive tracks and insulating materials, thermocouples). Inkjet inks can be classified into phase change inks, solvent-based, water-based and UV curable inks [5]. In our study, we have used solvent based Ag nanoparticle containing [6] and reactive silver inks and investigated their potential use for electronic applications. The wetting behavior, the curing strategy and the post production processing was investigated. Especially for metallic inks the post inkjet printing sintering step is crucial to achieve the desired conductivity. In case of inkjet printing on temperature sensitive substrates such as PET foils purely thermal treatment can not be used. Therefore, we have investigated other methods such as NIR radiation and photonic sintering. A further possibility to avoid high temperature thermal treatment is the use of reactive silver inks, which do not contain nanoparticles but dissolved silver complexes. After ink deposition, these complexes form metallic silver upon a mild thermal treatment. We have developed known reactive silver ink formulations from literature [7] further in respect to their printing and wetting properties. We will show the possibilities of both types of silver inks for inkjet printing of multilayer structures (1) consisting of UV-curable insulating inks (organic-inorganic hybrid material) and silver inks tracks as well as (2) thermocouples consisting of a two-layer structure of Pedot:PSS ink and silver inks.
This work was performed within the research projects “ANIIPF” and “MultiLINK”. Financial support by the Austrian Ministry for Transport, Innovation and Technology (bmvit) is gratefully acknowledged.
[1] C. Williams, Phys. World, 19 (2006) 24–29
[2] C.-W. Wang, W.-C. Chen, K. Cheng, L. Yuh-Zheng, International Conference on Digital Printing Technologies, Portland, (2007), 855–858.
[3] A. Lennon, R. Utama, A. Ho-Baillie, M. Lenio, N. Kuepper, S. Wenham, International Conference on Digital Printing Technologies, Portland, (2007). 882–885.
[4] F. Dijksman, P. C. Duineveld, M. J. J. Hack, A. Pierik, J. Rensen, J.-E. Rubingh, I. Schram, and M. M. Vernhout, J Mater Chem, 17 (2007), 511 – 522
[5] A. Hudd, Inkjet Printing Technology, in S. Magdassi, The Chemistry of Inkjet Inks, World Scientific publishing, 2010
[6] http://www.pvnanocell.com
[7] Walker, S. B.; Lewis, J. A. J. Am. Chem. Soc. 2012, 134 (3), 1419–1421, DOI:10.1021/ja209267c
8:00 PM - EM10.10.34
Facile Directed Assembly of Nanostructures via Directed Solvent Dewetting
Saleem Rao 2 , Lutfan Sinatra 1
2 Physics, King Fahd University of Petroleum and Minerals, Dhahran Saudi Arabia, 1 Division of Physical Sciences and Engineering, Solar and Photovoltaics Engineering Center, King Abdullah University of Science and Technology, Saudia Arabia (KAUST), Thuwal Saudi Arabia
Show AbstractOne-dimensional nanostructures-NS, such as nanoparticles, nano-cubes and nanotubes, represent the smallest dimension for efficient transport of electrons and excitons and thus are ideal building blocks for hierarchical assembly of functional nanoscale electronic and photonic structures. To harness these features in practical devices, it is indispensable to realize efficient methods for patterned assembly of NS at the micro/nano scale. Different methods like chemical interaction based to solvent driven, patterned assembly of NS have been reported. In this work, we report a large-scale patterned assembly of two different types of NS, Nanodiamond-ND and silver nanocubes-SNC on a solid substrate with and without directed solvent dewetting. In directed solvent dewetting process, Au surface is modified by self-assembled monolayer (SAM) to create hydrophobic and hydrophilic regions, to direct the solvent. Hydrophobic regions are created using a methyl (–CH3) terminated SAM of octadecanethiol molecules. By dipping SAM patterned substrate in NS suspension and letting it dry assembles the NS in the bare Au, wettable regions, shown in the Figure. Using this procedure, we successfully assembled the NS structures in the shape of dots, lines, and rectangles. And in a process of non-directed patterned assembly NS, SNC line patterns were created just by vertically dipping the silicon substrate in SNC solution. Evaporation of solvent assembled the SNC in line patterns on the substrate. In this solvent evaporation-driven process, less control over the frequency of line patterns and density of assembled SNC was observed. Subsequent photoluminescence imaging of the patterned NDs confirmed the presence of optically active NV centers. Patterned assembly of NDs and SNC at micron scale in different shapes using both the process will be presented. Effect of controlled and non-controlled dewetting on the shape and density of assembled NS will be discussed in detail.
8:00 PM - EM10.10.35
Uncovering the Mechanism for the Nucleation of Lead Sulfide Quantum Dots through a Hines Synthesis
Andrew Ruttinger 1 , James Stevenson 1 , Paulette Clancy 1
1 Robert F. Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, United States
Show AbstractSince their discovery in 1981, quantum dots (QD) have become an active research topic due to their striking optical, photovoltaic, and electronic properties. Nicknamed “artificial atoms,” QDs have a characteristic length scale in which energy levels are quantized; therefore, altering the size of the QD will control how energy is absorbed or emitted. QD diameter is highly tunable in the lab, with a narrow size distribution. Despite remarkable advances in the monodisperse synthesis of QDs, few theoretical studies have been conducted in an effort to understand their growth mechanism in solution due to difficulties in modelling these potentially large and complex systems. Nonetheless, without elucidating the growth mechanism it will be difficult to control QD size for large-scale manufacturing processes.
This paper uses ab initio Density Functional Theory (DFT) to propose a new mechanism for the synthesis of lead sulfide QDs, based on the experimentally well-established reaction between lead oleate and bis(trimethylsilyl)sulfide (Hines and Scholes, Adv. Mater. 2003). A study by Zherebetskyy et al. (Science, 2014) revealed fundamental insight into this QD synthesis: water is not only present in the reaction, but plays a crucial role in the QD formation. This observation was used to propose a mechanism for the QD synthesis, but does not present any kinetic information that could explain the tunable size of QDs.
Our contribution explores Zherebetskyy’s study and presents a minimum energy pathway (MEP) for both their posited mechanism and our own alternate mechanism. We use the popular Nudged Elastic Band algorithm to find the MEP. In our transition state DFT studies we used Ahlrichs' def2-TZVP basis set with B97-D3 and PW6B95 functionals, based on our investigations and recommendations by Grimme (Phys. Chem. Chem. Phys., 2011). Our results are validated by confirming Zherebetskyy’s findings of the facilitating role of water in the synthesis and by replicating their exothermic heat of reaction. However, our study presents two surprising new pieces of information. First, we find an unfavourable energy barrier associated with Zherebetskyy’s proposed mechanism. Second, we discover the likely existence of a lower-energy, hydrogen-bonded lead oleate dimer. Therefore, we predict an alternate mechanism that begins with a dimerization of lead oleate monomers. More importantly our results show that our mechanism, when compared with Zherebetskyy’s, proceeds through lower energy intermediates with a comparable activation energy and heat of reaction. Based on these results, QD synthesis will likely follow this dimer-based reaction. Moreover, we predict this causes QD nucleation to proceed through a polymerization-like process that stabilizes growth and explains QD monodispersity. Application of this study could be useful in future lab studies, and subsequent industrial scale-up of QD synthesis once sufficient experimental control of QD size has been achieved.
8:00 PM - EM10.10.36
High-Performance, Flexible, Transparent Film Heater with Uniform Metal Mesh Structures
Yoonkap Kim 1 , Sam-Soo Kim 1 , Jae-Sung Park 1 , DoYun Hwang 1 , Sung-Eun Park 1 , Gyuseok Choi 1
1 , Gumi Electronics & Information Technology Research Institute, Gumi Korea (the Republic of)
Show AbstractThe uniformly interconnected metal (CuNi, CuMg, Ni etc.) micromesh structures on polymer substrates have been fabricated using a simple transfer printing method for a flexible transparent heater. These metal micromesh structures on the diverse substrates exhibited an effective and rapid heating performance at low input voltages (below DC 9V). These results demonstrate that the high-performance is attributed to the creation of a high quality network over the whole surface area that can provide a relatively low sheet resistance (1.8-10 ohm per square), high transmittance, good mechanical flexibility, and strong adhesion to its substrate. In addition, the transparent heater showed the high thermal stability and reliability for outer bending and cycling tests. The flexible transparent heater based on the metal micromesh is therefore considered suitable operations as defogging/deicing systems for an automobile side-view mirror and camera lens, thermal cycling systems for polymerase chain reaction (PCR) devices, and particulate matter (PM) detecting systems for PM2.5 sensors.
8:00 PM - EM10.10.37
Directed Electrical Post-Processing of Printed Silver Ink for Improvement to Conduction and Microstructure
Peter Lewis 1 , Brian Smith 1 , Sara Barron 1 , T.S. Sriram 1 , Greg Fritz 1 , Vinh Nguyen 1
1 , Draper, Cambridge, Massachusetts, United States
Show AbstractTwo of the properties limiting mass adoption of printed silver for electronics are the materials relatively low conductivity and poor electrical stability. Here we present a post-processing technique that is easily implemented with commercially available silver inks and printers to increase the conductivity 2-5 times over processes available today. The resulting conductor’s properties more closely replicate extruded silver wire.
The published state of the art today in sintering silver inks results in a conductor which has high porosity and particle-particle interfaces which strongly scatter electrons. The high porosity foams suffer from small necking zones where current carrying capacity is greatly limited beyond what is expected from the nominal cross-sectional area. Furthermore, there are surface particles which are not greatly participating in the current flow since they are weakly connected to the conductive path.
Many attempts have been previously explored as a way to direct the silver atoms and particles into a more desired orientation without damaging the underlying substrate which may not be able to tolerate temperatures above 200 C. Utilizing thermal, laser, chemical, and photonic annealing have resulted in functionalization and significant improvements to the silver inks but are undirected in their scope and result in a porous foam conductor. Even upon high temperature substrates, there is a limit to the improvement in conduction after anneals since excessive heating results in silver segregation as the metal reduces its surface area to volume ratio and is no longer a conductive interconnect.
We present a process to improve printed silver’s performance without raising the temperature more than 20-30 Kelvin. An electrical process is utilized to reorient the silver particles to improve electron flow down the printed conductor. This is a directed process which unlike the common techniques, moves atoms and particles into the conductive path and grows the grain structure which results in significant improvements to both current carrying capacity, and conductivity through improvements in particle-particle scattering and porosity. This process results in smoother traces which are more amenable to further integration including multilevel circuitry.
8:00 PM - EM10.10.38
Wearable Dye Sensitized Solar Cells
Halil Yavuz 1 , Serkan Yetkin 1
1 Mechanical Engineering, Yuzuncu Yil University, Van Turkey
Show AbstractAfter the discovery of dye-sensitized solar cells (DSSC) in 1991, DSSC became a cheap alternative to conventional silicon-based p–n junction solar cells. The basic components of highly efficient dye-sensitized solar cells are an electrolyte system and dye absorbed photo-generator nanoporous oxide thick film covered by two highly transparent conducting oxides (TCO) thin film. Although it has relatively low efficiency for commercialization, it can be applied on the different advanced substrates such as textile based substrate According to the previous studies conducted regarding new type sensitizer, production of new type photoanode material and recycling electrolyte, the conversion efficiency of photovoltaic generation on DSSCs has been improved. Nevertheless, important parameters of light conversion efficiency resulting from the interactions between photoanode mesoporous material and TCO on the fleaxible substrates have been rarely studied. Although Dye Sensitized TCO materials is cheapest than other choices, there are two problems stemming from glass based TCO’s on DSSC applications. One of them is the production cost and the second one is the maximization of interaction in the interface area between ITO and the photoanodic TiO2 layer to reduce electron recombination. Both of problems can be solved by textile based produced sol-gel assist TCOs that gives the cheapest solution. In this study, Graphene-based (GBO) thin films has been produced on textile substrates (cotton) by sol-gel technique and these were used for the production of nanocrystalline dye-sensitized solar cells (nc-DSSC) to improve the photovoltaic performance that modifications help to increase the interaction in the interface area between the transparent conductive layer textile electrode and the photoanodic TiO2 layer, Structural, topographical and chemical analyses were performed using XRD, SEM and EDS. As a result of SEM analysis, it was confirmed that wearable -DSSCs in an improvement of 29 % 6% in the photon to energy conversion efficiency with respect to bare ITO system and 21 % incident photocurrent efficiency with respect to that ITO-based dye-sensitized solar cells.
8:00 PM - EM10.10.39
Graphene-Based Thermal Camufulage
Mohammed Salah Jalal 2 , Halil Yavuz 2 , Orcun Mert 1
2 Mechanical Engineering, Yuzuncu Yil University, Van Turkey, 1 Chemical Engineering, Yuzuncu Yil University, Van Turkey
Show Abstract“Defense Industry Plastics” emerge as extraordinarily tactically important materials as a result of developing world policies and the geographical environment that we exist in. Lots of monitoring techniques are developed in order to recognize hostile factors in defense technologies. As such, the most important innovation brought about in this area is the acquisition of hostile targets that are not detected by human eye, but by the detectors (thermal cameras) able to produce signals that are based on the principle of absorbing the long wave IR energy (heat). These detectors, by their nature of structure, work in two main functioning intervals; 3-5 µm or 8-12 µm. Camouflage is a tactical strategy to mislead and hide from enemy in natural environment. While it is possible to juke the apparent area detectors (bare eye cameras, classical cameras and so on) by various forms and patterns imitated from natural plants and soil texture, visual illusion (or camouflage techniques) requires expensive systems that are not easily applicable. Studies regarding the IR wavelength are diversified in new topics in the scientific world. Most important ones are the reduction in loss of soldiers during night and winter operations, and outer metallic coatings developed for tanks and heavy armored vehicles to infiltrate into operation zones without being detected. As can be inferred from the recent incidents, a large proportion of losses of soldiers and military vehicles in our country results from terrorist weapons modified by thermal cameras or IR controlled heavy vehicles.in this work It is aimed to obtain high performance National Thermal Camouflage Nano-Composite Plastics by designing innovative engineering plastics, developing their formations and synthesizing preliminary prototypes that will then be mass produced. It is also aimed to design materials that can be used in application areas especially in the defense industry, materials that rapidly decrease external dependence and are new generation, highly value-added and creative, tailored by innovative engineering approach. Structural, topographical and chemical analyses were performed using IR, XRD, XPS, TEM, SEM and AFM. Surprising results has been obtained after Graphene nanocomposite modification on plastic matrix. the %85 invisibility has been obtained in the thermal range. this is the best value in the literatures.
8:00 PM - EM10.10.40
Screen-Printed SnS Layers from Cubic and Orthorhombic Chemical Precipitates for Solar Cells
Rohini Neendoor Mohan 1 , Oscar GomezDaza 1 , Ana Rosa Garcia Angelmo 1 , M.T. Santhamma Nair 1 , P.Karunakaran Nair 1
1 , Universidad Nacional Autonoma de Mexico, Temixco Mexico
Show AbstractChemical bath deposition produces two types of SnS thin films – of a cubic structure, recognized as consisting of a unit cell with 32 SnS units and of an orthorhombic structure with 8 formula units per cell. The optical bandgaps (Eg) are distinct – the cubic (CUB) structured films with 1.7 eV and the orthorhombic (ORT), with 1.1-1-3 eV. A typical chemical bath deposition produces less than 20% of the Sn (II) as SnS thin films; the rest are left as precipitate. Since the two types of thin films are produced from different baths with distinct chemical compositions or at different temperatures from the same bath, the nature of the morphology of the precipitate differ in the two cases. In order to make a screen-printing paste of precipitate from the ORT-bath, adequate amount of triethanolamine (TEA) was added to it (0.05 g of SnS filtered-dried powder and 2 drops of TEA). The paste was printed using 60-120 mesh screen on to clean glass slide for basic studies or on a fluorine-doped tin oxide (FTO) glass with a chemically deposited CdS thin film (100 nm) for solar cell development. The as-deposited layer was dried on hot plate at 200 oC for 1 min, which produced an adherent layer on glass. Thickness of the layer was 5 μm. The XRD pattern of the film matches that of SnS-ORT. Diffuse reflectance spectrum of the layer showed an Eg of 1.3 eV. Heating the layer at 500 oC for 1h under N2 atmosphere (in presence of S) led to substantial increase by three orders of magnitude in p-type conductivity toward 10-5 Ω-1 cm-1. The annealed film has a high degree of orientation of (111) crystalline planes parallel to substrate plane, which is a normal feature of SnS-ORT films. This condition of heating is crucial to avoid partial conversion of the layer to SnS2, which is susceptible to turn the film to n-type. In this work we shall specifically address the following aspects as well – does the precipitate from the CUB-bath maintain the CUB-crystalline structure of the thin films; how does the finer morphology of this precipitate lead to more compact SnS layers for FTO/CdS/SnS/C-Ag cells; is it possible to make such solar cells with SnS-CUB, SnS-ORT layers with Eg 1.3 – 1.7 eV so that solar radiation is more effectively absorbed and hence leading to improved solar cell performance; etc. Currently these answers with implications in solar cell technology are being sought in our work.
8:00 PM - EM10.10.41
Feasibility of Spinodal Nanocomposite Fabrication by Diode Laser Melting of Wet Chemically Deposited Layers
Mykola Vinnichenko 1 , Karl-Heinz Heinig 1 2 , Marco Fritsch 1 , Hans-Juergen Engelmann 2 , Erik Schumann 2 , MIhails Kusnezoff 1
1 , Fraunhofer IKTS, Dresden Germany, 2 , Helmholtz-Zentrum Dresden-Rossendorf, Dresden Germany
Show AbstractNanocomposites with spinodal structure, where a nanowire network of one component is embedded in the matrix of the other one, possess intriguing electronic, mechanical and optical properties. For example, electronic band gap engineering has been realized for Si nanowire networks embedded in SiO2 which has a potential for application as a tailored absorber material in photovoltaics. So far, the metastable mixture of two immiscible components, e.g. Si and SiO2, has been deposited as SiOx film (02 nanocomposite either by solid state or by liquid state demixing.
Here, we propose a cost-efficient method to fabricate spinodal nanocomposite layers, which is investigated first for the Si-SiO2 model system. Instead of PVD or CVD growth of atomically mixed film, a layer based on mixed powder of 60 wt. % Si and 40 wt.% SiO2 (average particle size ~100 nm) was prepared by wet chemical deposition. For this purpose, an ink with 20 wt. % of the mixed powder was formulated and used for writing 1 mm wide and 1-2 µm thick linear patterns on fused silica wafers. These layers were rapidly heated in ambient air for ~5-15 ms using a micro-optically designed diode laser array (LIMO GmbH) at different laser powers.
Theoretical considerations suggest that fabrication of spinodal structures from granular layers requires their melting. Moreover, the melt heating to the temperatures above its miscibility gap is crucial to assure interdiffusion of the components to get a homogeneous liquid. During rapid cooling the melt reaches the miscibility gap, where it undergoes phase separation, however not again in a granular but in a spinodal structure. The quenching must not be too fast in order to allow complete spinodal decomposition, otherwise metastable SiOx is frozen into the solid state.
Cross-sectional energy filtered transmission electron microscopy (EFTEM) proves the predicted transformation pathway: the granular as-deposited layers convert into very homogeneous SiOx ones by laser treatment, with surfaces and interfaces becoming very smooth. This is a strong indication of the layer melting. Some micro-bubbles appearing in the layer are originating likely from decomposition of ink’s organic component. The phase separation 2SiO → Si + SiO2 during passing through the miscibility gap can be seen in EFTEM images as Si spheres surrounded by SiO2 precipitates, and in some cases, as small spinodal Si-SiO2 structures with ~40 nm characteristic structure size. The spinodal decomposition is not yet complete, i.e. the melt quenching is too fast leading to an insufficient transit time through the miscibility gap. Using thicker layers or different type of substrates should slow down the quenching resulting in complete spinodal phase separation.
8:00 PM - EM10.10.42
Luminescent Silica Nanomaterials—Synthesis, Characterization and Applications
Deepa Sriramulu 1 , Prashant Turaga 1 , Andrew Bettiol 1 , Suresh Valiyaveettil 1
1 , National University of Singapore, Singapore Singapore
Show AbstractLuminescent silica nanoparticles are interesting owing to their high stability and interesting photophysical characteristics. Many optically active compounds have been incorporated inside the silica nanoparticles and investigated their properties. Recently, we have synthesized and characterized luminescent ZnO-SiO2 nanoparticles (ZnOSiO2-X NPs) using reverse microemulsion method. The ZnO quantum dots formed during the synthesis was encapsulated and homogenously distributed inside the silica nanoparticles. The structural and optical properties of the nanoparticles were fully established using high-resolution micrographs and electron diffraction data. The ZnOSiO2-X NPs gave intense blue white luminescence and intensity varied with changes in composition of the particles. In addition to fluorescence emission, these particles showed phosphorescence emission in solution and in the solid state. ZnOSiO2/PDMS mixture was used in inkjet printing and mechanical stamping to prepare patterns which are light sensitive.
8:00 PM - EM10.10.43
Direct-Write Fabrication of Nanoparticle Suspensions for High-Density Interconnects
Alan Shen 1 , Anson Ma 2 1 , Sameh Dardona 3 , Callum Bailey 1
1 Department of Chemical and Biomolecular Engineering, University of Connecticut, Storrs, Connecticut, United States, 2 Polymer Program, University of Connecticut, Storrs, Connecticut, United States, 3 Physical Science Department, United Technologies Research Center, East Hartford, Connecticut, United States
Show AbstractThis paper presents a detailed study on the suitability of direct write (DW) technology for the fabrication of high-resolution wear sensing devices. The study is focused on understanding key device circuit requirements followed by materials selection and process development to meet such requirements. The study will also highlight the fabrication of high density parallel interconnect traces and provide recommendations for further improvement in materials formulations and process control. In this experiment, we fabricated high-density DW printed interconnect lines using silver particle concentrated pastes. In order to create the finest smooth print line possible, we simulated the volumetric flow rate through the assembly and looked at printing parameter’s influence on line geometry. The printed interconnects were sintered and subsequently characterized. The consistency of direct writing interconnects is further quantified in terms of the variation in dimensions and electrical conductivity of the printed and sintered lines.
This study presented ink formulation analysis for high resolution printing, utilized a novel approach to optimize the print line resolution and opened a new angle for additive manufacturing process control: line-to-line spacing. Parallel silver lines with 50 μm center-to-center spacing and 15 μm line width were achieved using nScrypt DW system. A couple of 150 μm spacing devices, close to aerosol jet printing resolution, were made to challenge the limit of extrusion-based (or micro-dispensing) DW. The printed and sintered silver lines are sufficiently conductive for displacement sensing applications.
Symposium Organizers
Santanu Bag, Air Force Research Laboratory
Edward (Ted) Sargent, University of Toronto
Patrick J Smith, The University of Sheffield
Teodor Todorov, IBM T.J. Watson Research Center
Symposium Support
MilliporeSigma (Sigma-Aldrich Materials Science)
NovaCentrix
Strem Chemicals, Inc.
EM10.11: Oxide-Based Electronics II
Session Chairs
Arokia Nathan
Patrick J Smith
Friday AM, December 01, 2017
Hynes, Level 1, Room 103
8:00 AM - EM10.11.00
Fused Polymers for Organic Field Effect Transistors via Metal-Free Aldol Polymerisation
Ada Onwubiko 1
1 , Imperial College London, London United Kingdom
Show AbstractPolymers for use in semiconducting polymers are generally synthesised using metal-mediated coupling reactions, which connect monomers via single bond carbon-carbon bonds. These monomers, in turn, are strategically designed to be co-planar, centrosymmetric with extended aromatic centres. These features elicit close Van der Waals and pi-pi interactions which facilitate formation of micro and macromolecular organisation suited for high charge mobilities. However, miscoupling along the polymer backbone during metal-mediated polymerisation reactions, and the intrinsic conformational disorder arising from the single bond linkages limit charge delocalization and the formation of optimal morphology for charge transport. We propose the use of the simple aldol condensation to introduce rigid carbon-carbon double bonds between polymer building blocks thus eliminating rotational freedom along the conjugated backbone. This aldol polymerisation offers a “green” synthetic route to organic semiconducting polymers, without the need for transition metals catalysts, organometallic monomers or the steps required to remove their side-products. We introduce rigid, fused electron deficient polymers with high electron affinity and exhibit NIR absorption and stable electron transition organic field-effect transistors.
8:15 AM - EM10.11.01
High Performance Oxide Thin-Film Transistors with Inkjet Printed Ag Source-Drain Electrodes
Liam Gillan 1 , Jaakko Leppäniemi 1 , Himadri Majumdar 1 , Ari Alastalo 1
1 , VTT Technical Research Centre of Finland, Ltd., Espoo Finland
Show AbstractFully inkjet printed fabrication of thin film transistors (TFTs) is desirable to enable reproducible, high throughput, low cost production of electronics under mild conditions. However, TFT devices fabricated from printable materials typically exhibit inferior performance to those of non-printed. For example, there is a lack of well-performing printable source-drain electrode materials for oxide semiconductors. In contrast to vacuum-deposited Al, printed Ag has a high contact resistance and work function, with poor charge carrier injection to the semiconductor. Therefore, there is a requirement to improve electrical performance of TFTs incorporating printed electrode material such as Ag. A possible approach to achieve this is by engineering of the semiconductor-contact interface.
Reference devices were prepared following a reported method using samples comprising p-Si gate electrode, SiO2 dielectric, and inkjet printed In2O3 semiconductor with vacuum deposited Al source drain contact electrodes.[1] This solution-based processing method limited the thermal budget to 300°C.[2] Devices were also fabricated using inkjet printed Ag source drain contacts. Devices with Al electrodes provided a charge carrier saturation mobility of 4.3 ± 0.9 cm2 / (Vs), whereas those with Ag contacts exhibited an expected lower mobility of 8.0*10-3 ± 3.9*10-3 cm2 / (Vs). Interfacial engineering of devices with Ag contacts significantly increased the saturation mobility to 3.1 ± 0.5 cm2 / (Vs).
This work yielded TFTs possessing printed Ag contacts that display electrical performance comparable with devices incorporating vacuum-deposited Al contacts. The impact of this result is the possibility for low temperature solution based roll-to-roll production of high performance TFT devices.
[1] J. Leppäniemi, K. Eiroma, H. Majumdar, and A. Alastalo, “Far UV annealed inkjet-printed In2O3 semiconductor layers for TFTs on flexible PEN-substrate,” ACS Appl. Mater. Interfaces, vol. 9, pp. 8774–8782, 2017.
[2] J. Leppäniemi, O. H. Huttunen, H. Majumdar, and A. Alastalo, “Flexography-Printed In2O3 Semiconductor Layers for High-Mobility Thin-Film Transistors on Flexible Plastic Substrate,” Adv. Mater., vol. 27, no. 44, pp. 7168–7175, 2015.
8:30 AM - EM10.11.02
Solution Processed Yttrium-Doped Zinc Tin Oxide with Superior Performance at Very High Voltage
Alexis Marette 1 , Samuel Rosset 1 , Herbert Shea 1 , Danick Briand 1
1 , Ecole Polytechnique Federale de Lausanne, Neuchatel Switzerland
Show AbstractWe report on a solution processed zinc-tin oxide semiconductor doped with yttrium for thin-film transistors (TFT) operating at 1 kV drain-source voltage. Flexible high voltage TFTs (HVTFTs) can be integrated as switches to drive compliant high-voltage devices such as dielectric elastomer actuators, triboelectric generators, and X-ray sources. HVTFTs can operate up to 1 kV drain-source voltage thanks to structural features such as a thick dielectric layer with high breakdown field, and an offset gate. However, those features result in low subthreshold swing and high off-current at high-voltage in addition to high electric field effects leading to degraded characteristics (electron velocity saturation, injection barrier, leakage current, space-charge limited current and channel length modulation). This work investigates the reduction of these high-voltage effects by adding up to 5% yttrium to the zinc and tin cations in the semiconductor thin-film. Electronic and material properties were characterized and the results showed that the addition of Yttrium improves significantly the performances of ZTO TFTs at very high voltages.
The TFTs are designed to operate at 1 kV. The channel length is 500 µm it width is 5 mm to avoid short and narrow channel effects. The substrate is made of polyimide coated with 20 nm Al2O3. The semiconductor precursors are zinc chloride and tin chloride (Z:T = 2:1). We studied the devices produced by adding from 0% up to 5% mass yttrium chloride to the solution. To operate at 1 kV, the dielectric is a bilayer made of 100 nm thick Al2O3 and 1 µm thick Parylene-C. The gate is defined by an aluminum electrode and is offset from the drain (by 150 µm).
The TFTs transfer characteristic was measured at 1kV. The YZTO transfer curve exhibited a steeper subthreshold slope than for pure ZTO with a subthreshold swing of 20 V/dec for YZTO and 35 V/dec for ZTO. Interestingly, the drain-source leakage current dropped by two order of magnitudes to 40 nA. The threshold voltage at a drain source voltage of 1 kV passed from -10 V for ZTO to 6 V for YZTO, allowing complete operation in the positive gate voltage range. Considering HVTFTs for logic applications, the potential injection barrier dropped from 110 V for ZTO to 60 V for YZTO, which would provide lower output voltages. These electrical measurements were supported by different materials characterizations, such as X-ray Photoelectron Spectroscopy). The deconvolution of the oxygen peaks showed a higher concentration of oxygen vacancies with respect to metal oxide bonds in the yttrium doped ZTO film in comparison to the undoped ZTO film, demonstrating that yttrium has an impact on the ZTO structure. This study shows that the addition of yttrium in ZTO is beneficial for the operation of thin film transistor at very high voltages. Ongoing work involving printing of ZTO and YZTO towards fully printed transistors will be also presented at the conference.
8:45 AM - EM10.11.03
Enhanced Photocurrent Generation in Solution-Processed Zinc Oxide Nanorods Array by Incorporating Al3+
Retno Miranti 1 , Nobuhiro Matsushita 2
1 Department of Electrochemistry, Tokyo Institute of Technology, Yokohama Japan, 2 Department of Materials Science and Engineering, Tokyo Institute of Technology, Tokyo Japan
Show AbstractAluminum-doped Zinc Oxide (AZO) nanorods array was fabricated by solution process named spin-spray at a temperature below 100oC. The ZnO: Al nanorods were prepared using low-cost precursor Zn(NO3)2･6H2O and Al(NO3)3･9H2O as starting material for Zn2+and Al3+ respectively. The reaction solution was prepared by mixing NH3 as pH controller. These solutions are sprayed continuously on the heated spinning table, and the scheme of the deposition process is described elsewhere. Zinc Oxide (ZnO) with wide direct bandgap (3.4 eV) and large exciton binding energy (60 meV) is a promising functional material in optoelectronic application. These properties can be modulated by varying the nanostructures such as nanorod, nanofibers, nanotubes, etc. Recently, AZO has been studied intensively due to its high carrier concentration generated by the Al3+ occupation in the Zn interstitial sites. The AZO reported in the literature mostly used as a transparent conducting material. However, there was only a few research in the AZO nanorods especially synthesized by low-temperature solution process. In this research, AZO nanorods were successfully deposited by solution process at 90oC, and the enhancement of photocurrent generation due to Al doping was investigated. The as-prepared AZO nanorods were growing vertically along c-axis with the structure of wurtzite-type ZnO observed by X-ray Diffractometer (XRD). X-ray Photoelectron Spectroscopy (XPS) indicated that Al3+ was successfully incorporated into ZnO lattice. The decrease in the nanorods diameter from 400nm to 250nm due to 5% Al doping was observed by Scanning Electron Microscopy (SEM). The photocurrent response was determined by using the electrochemical system, and the photocurrent density was about 0.2 mA/cm2. The 5% AZO showed higher on-off ratio in photoswitching which illustrated the high dependency of Al content in ZnO crystal.
9:00 AM - EM10.11.04
Excimer Laser Annealing of Solution-Processed InZnO Thin Film
Juan Paolo Bermundo 1 , Yasuaki Ishikawa 1 , Mami Fujii 1 , Chaiyanan Kulchaisit 1 , Hiroshi Ikenoue 2 , Yukiharu Uraoka 1
1 , NAIST, Ikoma Japan, 2 Department of Gigaphoton Next GLP, Kyushu University, Kyushu Japan
Show AbstractOxide semiconductors (OS) are popular materials because of their high mobility, low temperature fabrication, and wide bandgap.1 Recently, research on solution processed OS have increased due to its simplicity and versatility, with ZnO, InGaZnO, and InZnO lately becoming the focus.2 Nevertheless, an issue with the solution process route is the need for higher annealing temperatures typically around 400 °C and multiple lengthy annealing processes (>1 h) to complete M-O bond formation and compete with the performance of vacuum-processed OS. Thus, a low temperature and rapid annealing method is needed for advanced applications of solution-processed OS. We have previously reported that excimer laser annealing (ELA) is a low temperature method (<30°C) that improves the characteristics of vacuum processed a-IGZO thin-film transistors (TFT).3 Here, we report the use of ELA on solution-processed InZnO TFTs. The instantaneous (<100 ns) and low substrate temperatures after ELA are indispensable in flexible applications.
An aqueous InZnO precursor was spin-coated on a heavily doped n-type Si substrate with a 100 nm thermal oxide SiO2 layer. Si (ρ<0.002 Ω●cm) and SiO2 are the gate and gate insulator, respectively. After spin-coating the 10 nm InZnO thin-film, a 2-step baking process was performed: 150°C for 5 min then 300°C for 1 h to evaporate the solvent and complete film fabrication, respectively. The InZnO channel was then patterned by photolithography and wet etching. Subsequently, a set of samples were subjected to UV/O3 treatment at 290°C for 15 min while another set were not. A stack of Mo/Pt (80/20 nm) were deposited as source/drain electrodes of the bottom gate top contact TFT. Instead of a customary furnace post-annealing at 300°C, all TFTs were irradiated by a single shot of a KrF excimer laser (λ=248 nm) at a fluence (F) of 80 mJ/cm2. Evaluation of electrical characteristics show that TFTs subjected to both ELA and UV/O3 had an average field effect mobility (μFE) of 1.49 cm2/Vs and Von (V at 1 nA) of -0.33 V. On the other hand, TFTs subjected only to ELA had a comparable average μFE of 1.09 cm2/Vs and Von of 1.46 V.
We also analyzed the effect of ELA on the sheet resistance (Rs) of solution-processed InZnO thin-films. Without irradiation, the Rs of InZnO is very high (>106 Ω/sq). After ELA at 80 mJ/cm2 in ambient atmosphere, Rs decreased by almost 2 orders of magnitude to a still high value of 3.35×104 Ω/sq. Increasing F to 120 mJ/cm2 and irradiating in vacuum (<10-3 Pa) dramatically reduced Rs to 298.16 Ω/sq. These results show that ELA is a promising instantaneous and low temperature annealing method for solution-processed InZnO TFT and can induce direct transformation of InZnO into a conductive oxide.
We thank Nissan Chemical Industries, for providing the InZnO precursors.
1. T. Kamiya et al., Sci Technol Adv Mater 11, 044305 2010
2. S. J. Kim et. al. Jpn. J. Appl. Phys. 53, 02BA02 (2014)
3. J.P. Bermundo et al., J Phys D: Appl Phys, 49, 035102 2016
9:15 AM - EM10.11.05
Fuel-Assisted Low-Temperature Combustion Chemistry in Solution-Processed Metal Oxide Semiconductors for Thin-Film Transistors
Binghao Wang 1 , Matthew Leonardi 1 , Tobin Marks 1 , Antonio Facchetti 1
1 , Northwestern University, Evanston, Illinois, United States
Show AbstractOwing to high carrier mobilities, good environmental/thermal stability, excellent optical transparency, and compatibility with solution processing, thin-film transistors (TFTs) based on amorphous metal oxide (a-MO) semiconductors are promising alternatives to amorphous silicon (a-Si:H) and low temperature (< 600 °C) poly-silicon (LTPS). However, solution-processed display-relevant indium-gallium-tin-oxide (IGZO) TFTs suffer from low carrier mobilities and/or inferior bias-stress stability versus their sputtered counterparts. Here we report that three types of environmentally benign carbohydrates (sorbitol, sucrose, and glucose) serve as especially efficient assisting fuels for IGZO film combustion synthesis to yield high-performance TFTs. The results indicate that these carbohydrates assist the combustion process by lowering the ignition threshold temperature and, for optimal stoichiometries, enhancing the reaction enthalpy. IGZO TFT mobilities are increased to >8 cm2 V-1 s-1 on SiO2/Si gate dielectrics with significantly improved bias stress stability. The first correlations between precursor combustion enthalpy and a-MO densification/charge transport are established. In following work, we compared chemically and compositionally very different co-fuels (urea, glycine, sorbitol and L-ascorbic acid) to explore the essence of fuel-assisted combustion reaction using indium gallium zinc oxide (IGZO) as a semiconductor platform. DSC and TGA analysis show that all co-fuels enable a substantial reduction (-67 °C for L-ascorbic acid) in the combustion igniting temperatures. Optimal co-fuel contents result in low residual weights after combustion process and significantly intensify the combustion process, which enhance the IGZO film densification, lattice formation and enhance IGZO transistor charge transport and bias-stress stability. By systematically investigating the physical and chemical characteristics of the IGZO precursors, we concluded that the metal ion-co-fuel interactions, acid-base property, enthalpy of combustion and decomposition features of these co-fuels are the reliable predictors for highly efficient combustion processes.
10:00 AM - *EM10.11.06
Oxide Nano-Electronics—Device Circuit Interations and Near-OFF State TFT Architectures
Arokia Nathan 1 , Chen Jiang 1 , Xiang Cheng 1 , Guangyu Yao 1 , Hanbin Ma 1 , Hyung Choi 1
1 , University of Cambridge, Cambridge United Kingdom
Show AbstractOxide semiconductors are becoming a key material for future electronics because of their wide band gap, hence high transparency and low OFF current, compared with the ubiquitous silicon and organic thin-film technologies. This talk will review the new generation of applications using oxides ranging from large area electronics to the newly emerging areas such as the Internet of Things. While the oxide transistor continues to evolve, producing devices with higher mobility, steeper sub-threshold slope and lower threshold voltage, practical circuits are constrained by issues related to non-uniformity, electrically- and illumination-induced instability, and temperature dependence. We will discuss the critical design considerations to show how device-circuit interactions should be handled and how compensation methods can be implemented. In particular, the quest for low power becomes highly compelling in newly emerging application areas related to wearable devices in the Internet of Things. We will discuss thin-film transistor operation in the different regimes, and review device properties when operated in the deep sub-threshold regime or in near-OFF-state, addressing the pivotal requirement of low supply voltage and ultralow power leading to potentially battery-less operation.
10:30 AM - EM10.11.07
Solution Based Low Temperature Fabrication of Silicon Dioxide Thin Films by Mist-CVD
Shigetaka Katori 1 , Kouki Hiramatsu 1
1 , National Institute of Technology, Tsuyama College, Tsuyama Japan
Show AbstractSilicon oxide film has high insulating properties and plays an important role in electrical industries. In recent years, printed electronics that produce solar cells and light emitting devices by printing technology attracts much attention. Especially, formation of an organic semiconductor thin films has been studied by an inkjet printing etc. Meanwhile, in order to manufacture a thin film transistor by a printing technology, it is necessary to prepare not only an active layer but also a high-quality gate insulating films. However, there is no effective technique for forming a high quality silicon dioxide thin film by a printing technology.
We have been discussed solution based thin film forming technique using ultrasonic assisted spray deposition (Mist-CVD). This deposition methods are one of most effective film formation technique under atmospheric pressure, which enables to form zinc oxide, gallium oxide, polymer and etc. In this study we discuss spray deposition of silicon dioxide thin films under low temperature and atmospheric condition. Polysilazane solution (solvent: butyl acetate) and hydrogen peroxide solution 6% (diluted with distilled water) are used for source material, and controlled the substrate temperature, carrier gas concentration as forming parameters. The stage on which the substrate was fixed and film formation was carried out. Forming temperature is ranging from 50 to 250° C and a film forming time of 15 min, and these mixing gas sprayed on the glass substrate. Particularly, to study the optimum film formation rate, the spray angle of the nozzle tip was changing. To characterize the film properties, morphology, thickness, Fourier-transform infrared spectroscopy (FT-IR), reflective index were measured.
In the polysilazane solution, a strong peak was observed around 850 (cm -1), 950 (cm -1), which based on stretching vibration of Si-N bonds and Si-H bonds present in the polysilazane molecule. On the other hand, in the case of formed films, the peaks derived from the Si - N bond and the Si - H bond disappeared except the film forming temperature was 50 ° C, and a strong peak derived from the Si - O bond was observed around 1230 (cm -1). This peak was also observed when the film formation temperature was 70 ° C. Further, the refractive index was measured by spectroscopic ellipsometry, it was 1.46, which was consistent with the value of the silicon dioxide films. Furthermore, it was confirmed that the optimum spray angle was in the range of 5 ° to 30 °.
10:45 AM - EM10.11.08
Rapid Laser-Induced Photochemical Conversion of Sol-Gel Precursors to In2O3 Layers and Their Application in Thin-Film Transistors
Nikolaos Kalfagiannis 1 , Spilios Dellis 1 , Ivan Isakov 2 , Kornelius Tetzner 2 , Thomas Anthopoulos 2 3 , D. Koutsogeorgis 1
1 , Nottingham Trent University, Nottingham United Kingdom, 2 , Imperial College London, London United Kingdom, 3 , King Abdullah University of Science and Technology, Saudia Arabia (KAUST), Thuwal Saudi Arabia
Show AbstractThin-film transistors based on transparent metal oxide semiconductors hold great promises for a variety of emerging applications in large-area electronics. Despite the huge promise, however, accurate control over the morphology and the chemical composition of solution-grown metal-oxides still remains challenging, leading to significant device-to-device performance variations. In addition, deposition of semiconducting metal oxides by “sol-gel” has so far been limited to high processing temperatures, typically in excess of >350 °C, rendering the technology incompatible with inexpensive, temperature-sensitive substrates such as plastic, the material of choice for large-scale roll-to-roll (R2R) processes. This post-deposition heat treatment is a major obstacle that hinders the integration of heat-sensitive flexible polymeric substrates. Therefore, it is essential to develop alternative methods of processing that can meet the demands relevant to this area. Thermal annealing at reduced processing temperature, ideally less than 150 °C, has been examined aiming at oxide TFTs fabrication on flexible polymeric substrates. However, the processing times that are typically required are very long (up to 4 h) and the achieved TFTs performance and stability are largely inadequate for real electronic applications.
Optical annealing can be viewed as a powerful tool towards low-temperature fabrication schemes, however, recent reports on optical sintering suffer from lengthy exposure that renders the process unsuitable for high throughput R2R manufacturing. Therefore, alternative methods that can deliver rapid and scalable materials processing are urgently required. To this end, Laser Annealing (LA) offers fast processing along with rapid, precise and selective energy delivery in area and depth via critical laser energy absorption. In this study, the feasibility of the incorporation of Laser Annealing in the fabrication process of metal oxide TFTs was investigated. High-performance In2O3 based TFTs were prepared via a "sol-gel” method accompanied with a Laser Annealing step. TFTs with electron mobility up to 13 cm2/Vs and with low gate current were fabricated. The high performance is accompanied by the elimination of the need of the semiconductor patterning; hence significantly reducing the fabrication complexity and cost.
11:00 AM - EM10.11.09
Solution Processed Perovskite Oxide Nanocrystals and Nanocomposite Formulations for Applications in Printed Dielectrics
Stephen O'Brien 1 2 3
1 , The City College of New York, New York, New York, United States, 2 PhD Program in Chemistry, The Graduate Center CUNY, New York, New York, United States, 3 , The CUNY Energy Institute, New York, New York, United States
Show AbstractNanocomposite materials are attractive candidates for the dielectric layer in capacitors. The prospect of designing a nanocomposite dielectric, by combining colloidal nanoparticle fillers and polymer hosts, lends itself very well to tunability of the mechanical and electrical properties. Further, designing capacitors using nanotechnology principles could result in high throughput fabrication/manufacturing techniques such as printing or r2r. A parallel plate capacitor is a deceptively simple device concept that quickly evolves into a complex problem when considering how components can be assembled into the dielectric layer to optimize for comprehensive performance, as a function of capacitance, frequency, voltage, leakage, dissipation loss and ESR. Our work in solution processing of inorganic oxide dielectrics and multiferroics, using a modified sol-gel approach allows for the preparation of a variety of formulations that can be treated as inks for deposition as layers and/or for the design of novel nanocomposite films.
11:15 AM - EM10.11.10
Synthesis and Sintering Methods of Ultra-Small Colloidal ZnO Nanocrystals for Solution-Processed Thin-Film Transistors on Plastic
Yuhang Sun 1 , Adam Weidling 1 , Sarah Swisher 1
1 , University of Minnesota Twin Cities, Minneapolis City, Minnesota, United States
Show AbstractSolution-processed metal oxide semiconductors (i.e. ZnO) produced using sol-gel methods have demonstrated promising results for next-generation flexible electronic devices. However, colloidal nanocrystal inks offer several advantages over sol-gels for thin-film transistors (TFTs): the crystallinity and stoichiometry of the semiconductor nanocrystals can be precisely controlled during the synthesis, and the nanocrystal surfaces can be functionalized with ligand molecules to improve ink stability and control ink spread during printing. Further exploration and optimization of nanocrystal inks is needed to realize high-performance oxide semiconductors at plastic-compatible temperatures. In this work, we have synthesized ultra-small ZnO nanocrystals by reacting zinc acetate with sodium hydroxide in isopropanol, and adding dodecanethiol as the encapsulant. Using transmission electron microscopy, we confirmed that the resulting nanocrystals are roughly spherical and uniformly-sized with a diameter of 3.6 +/- 0.7 nm. The interatomic spacing deduced from electron diffraction patterns match the 002, 110, and 112 peaks of wurtzite ZnO. The ZnO nanocrystals will be employed as the channel material in air-stable, solution-processed TFTs, which benefit from a post-deposition sintering process to improve electron transport by removing the long-chain organic ligands. Thus we will compare the effects of a traditional high-temperature sintering process with a rapid photonic curing process. Photonic curing uses a brief, intense pulse of broad-spectrum light to heat a thin film without damaging the underlying substrate. This may enable more efficient sintering of metal oxides on flexible plastic films. To determine the ligand residue in the ZnO film after sintering, we have investigated the vibrational spectra and elemental analysis of as-deposited and sintered ZnO thin films using Fourier-transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS). We find that the long-chain organic ligand are completely removed from the ZnO thin film after sintering the film in a tube furnace at 250 C for 90 minutes, but most plastic substrates cannot withstand this temperature. Interestingly, the same result can be achieved using a photonic curing process taking less than 100 microseconds. Experiments are underway to determine how ligand removal impacts transport through the TFT channel, and to quantify crystallite growth using x-ray diffraction. This study will elucidate the critical relationship between the residual ligand content in the nanocrystal film, the nanocrystal size, and electron transport in TFTs, thus providing guidance to optimize a wide range of metal oxide nanocrystal devices.
11:30 AM - EM10.11.11
Transparent and Ink-Jet Printed Piezoelectric Structures from Sol-Gel Solutions
Sebastjan Glinsek 1 , Nicolas Godard 1 , Daniele Sette 2 , Stephanie Girod 1 , Emmanuel Defay 1
1 , Luxembourg Institute of Science and Technology, Belvaux Luxembourg, 2 , Primo1D, Grenoble France
Show AbstractChemical-solution-deposition-derived thin films integrated with silicon technologies have been intensively studied for the last 20+ years and the cost-efficient technology have reached industrial maturity. In the quest for devices with extended functionalities, investigations of the integration of piezoelectrics with non-silicon substrates are needed. In addition, direct patterning of the structures would further reduce the production costs. In this contribution we will show that ink-jet printed and transparent piezoelectric structures, with state-of-the-art functional properties and large potential for haptic applications in consumer electronics, can be prepared by innovative sol-gel processing.
The lead zirconate titanate (PZT) solutions, with near-morphotropic-phase-boundary composition, were prepared from transition metal alkoxides and dehydrated lead(II) acetate in 2-methoxyethanol solvent. Nano-scale clustering was diminished by modification of the alkoxides with β-diketonate. Reflux was performed for several hours and the reaction by-products were removed by distillation.
As prepared solutions were spin coated on 2’’ fused silica substrates and perovskite films were obtained after crystallization between 600 and 700 °C. Buffer layers between the PZT and glass substrate were used to relax thermal stresses and control the orientation. By repeating the deposition-heating steps crack-free films with thicknesses up to 1.6 μm were obtained. Transmittance of the structures, measured in the visible spectrum, is above 0.6. The 880 nm-thick films have 100 Hz-remanent polarization of 22 μC/cm2 and 1 kHz-dielectric permittivity and losses of 1100 and 0.03, respectively, all measured in-plane. Transducer structures were formed by patterning interdigital electrodes. The structures were driven at 40 V peak-to-peak and a standing acoustic wave was achieved at 116 kHz, with peak-to-peak out-of-plane actuation of 132 nm and in-plane wavelength of 7 mm. The transparent PZT structures are promising for haptic textural sensation applications.
The very same PZT solutions were used also for the ink-jet studies, however, to adjust ink viscosity and surface tension for efficient droplet ejection ethylene glycol and glycerol co-solvents were added. Printing was performed on standard platinized silicon substrates, which have very high surface energy of ~ 1 J/m2, therefore self-assembled monolayers have been used to constrain ink spreading. Arrays of 500×500 μm2 PZT squares were printed, dried and crystallized at 700 °C. By optimized design of the solutions and drying procedure the “coffee-stain” effect was abstained and structures with uniform thicknesses up to 300 nm were successfully produced. Raman and XRD studies confirmed crystallization in the perovskite phase. The 160 nm-thick printed structures show state-of-the-art electrical properties, with 10-kHz dielectric permittivity and losses of 600 and 0.03, respectively, and remanent polarization of 23 μC/cm2.
11:45 AM - EM10.11.12
High-Resolution Patterning of Infrared Quantum Dot-LEDs via Inkjet Printing
Giovanni Azzellino 1 , Francesca Freyria 2 , Michel Nasilowski 2 , Moungi Bawendi 2 , Vladimir Bulovic 1
1 Electrical Engineering and Computer Science, MIT, Cambridge, Massachusetts, United States, 2 Chemistry, MIT, Cambridge, Massachusetts, United States
Show AbstractWe adopt inkjet printing to demonstrate high-resolution patterning of colloidal quantum dot light-emitting devices (QD-LEDs). By tailoring the solvents of QD solutions and by engineering the surface of the layer underlying the printed QD films, we obtain continuous and pinhole-free QD films with a pitch of 50 μm, using single-droplet prints. With the latest generation of ‘hybrid’ QD-LED architecture1,2, we are able to report efficient near infrared-emitting QD-LEDs that can be patterned with high yield over large area. This work addresses the challenge of QD patterning over arbitrarily-sized area and advances the development of inkjet-printed QD-LEDs, as needed in the fabrication of high quality QD pixels in efficient multi-color LED applications.
The high luminescence efficiency and uniquely size-tunable color of solution-processable semiconducting colloidal quantum dots (QDs) highlight their potential for use as both optically- and electrically-excited luminophores in energy-efficient, substrate-independent, high-color-quality solid-state lighting and thin-film display technologies1. Recent advances in the design of electrically-driven QD-LEDs have seen their external quantum efficiencies approach the record of 20% in the visible and 4% in the near infrared1, 2.
Inkjet printing offers a new, largely unexplored technique for room temperature, maskless pattering of QD-LEDs. Since the technique relies on solvent – and not solute – tailoring, it is readily translatable to most QD solutions, without affecting their optical properties.
1. B. S. Mashford, et al. Nat. Photonics, 7, 407 (2013).
2. G. J. Supran et al. Adv. Mater. 27, 1427-1422 (2015)
EM10.12: Earth-Abundant Chalcogenides
Session Chairs
Edgardo Saucedo
Ayodhya Tiwari
Friday PM, December 01, 2017
Hynes, Level 1, Room 103
1:30 PM - *EM10.12.01
Formation, Doping, and Grain Growth of Kesterites and Chalcopyrites from Molecular Inks to Form High Efficiency Single Junction Cells and Tandems Cells with Hybrid Perovskites
Hugh Hillhouse 1
1 , Univ of Washington, Seattle, Washington, United States
Show AbstractConventionally, thin film sulfide or selenide solar cells have been synthesized by evaporating or sputtering metals followed by sulfurization or selenization. More recently, potentially low-cost high-throughput approaches have been demonstrated that form the chalcogenide directly from nanoparticle or molecular inks. The highest efficiency devices have been prepared by processes utilizing hydrazine as a solvent and complexing agent. Here, we present our progress to develop of a class of solution-phase routes to Cu2ZnSn(S,Se)4 and Cu(In,Ga)(S,Se)2 that do not use suspensions of nanoparticles or hydrazine. We have developed a DMSO/thiourea solvation/complexation chemistry that yields 11.8% efficient CZTSSe solar cells [1], 13.0% efficient CISSe and 14.7% efficient CIGSSe [2]. We have discovered new effects of alloying and doping using a combinatorial ultrasonic spray coater and high-throughput screening method to map the optoelectronic properties of the chalcogenide absorber. The presentation will focus on: (a) the formation of films and elimination of impurities from precursors in the ink, (b) incorporation of group I dopants, particularly lithium, and their effects of absorber properties and grain boundaries[1], (c) germanium alloying to form Cu2Zn(Sn,Ge)(S,Se)4 with record high open circuit voltage relative to the maximum theoretical open circuit voltage for the bandgap [3], (d) a new understanding of grain growth and group I element transport in CZTS [4], and (e) recent results to yield tandem solar cells with hybrid perovskites [5].
[1] Xin, H., Vorpahl, S.M., Collord, A.D., Braly, I.L., Uhl, A.R., Krueger, B.W., Ginger, D.S., Hillhouse, H.W., Phys. Chem. Chem. Phys. 17, 23859-23866 (2015).
[2] Uhl, A.R., Katahara, J.K., Hillhouse, H.W., Energy & Environmental Science 9, 130-134 (2016).
[3] Collord, A.D., Hillhouse, H.W., Chem. Mater. 28, 7, 2067–2073 (2016).
[4] Clark, J.A., Hillhouse, H.W., In preparation.
[5] Uhl, A.R., Yang, Z., Jen, A.K.-Y, Hillhouse, H.W., J. Mater. Chem. A 5, 3214-3220 (2017).
2:00 PM - EM10.12.02
Solution Spin-Coated Cu2ZnSnS4 on TiO2 Nanorod Forest Films with Engineered Interface for High Sensitivity Photodetectors and Solid State Solar Cells
Zhuoran Wang 1 , Nicolas Brodusch 1 , Raynald Gauvin 1 , George Demopoulos 1
1 , McGill University, Montreal, Quebec, Canada
Show AbstractCu2ZnSnS4 (CZTS), other than in standard p-n junction device architecture, can be employed as broad light absorber upon coating onto a wide bandgap electron conducting TiO2 film.1,2 Earlier CZTS sensitized TiO2 films have yielded low photoconversion efficiency and Voc.3 In this work, a water-ethanol solution spin coating approach has been applied to directly deposit CZTS nanocrystallites on rutile TiO2nanorods grown on FTO substrate (TNR) as an alternative to the multi-step sequential deposition, and improved energy conversion efficiency was achieved.4 Furthermore, interface engineering is realized by applying an insulating thin layer to the Cu2ZnSnS4-TiO2 interface. This treatment is proven to have improved the band alignment. EDS f-ratio mapping and XANES are used to confirm the purity and homogeneity of CZTS.The new engineered CZTS-TiO2 nanostructure shows promise in building high sensitivity photodetectors or all-solid state solar cells.
Wang, Z.; Demopoulos, G. P.,Crystal Growth & Design 2016, 16 (7), 3618–363
Wang, Z.; Elouatik, S.; Demopoulos, G. P., Physical Chemistry Chemical Physics 2016, 18 (42), 29435-29446.
Wang, Z.; Demopoulos, G. P., ACS Appl Mater Inter 2015,7 (41), 22888-22897.
Wang, Z.; Gauvin, R.;Demopoulos, G. P., Nanoscale2017,DOI : 10.1039/C7NR01422H
2:15 PM - EM10.12.03
Ternary Lead-Chalcogenide Semiconducting Films Grown by Aqueous Spray Deposition
Hussain Abouelkhair 1 , Pedro Figueiredo 1 , Seth Calhoun 1 , Chris Fredricksen 1 , Robert Peale 1 , Isaiah Oladeji 2
1 , University of Central Florida, Orlando, Florida, United States, 2 , SISOM Thin Films LLC, Orlando, Florida, United States
Show AbstractTernary lead chalcogenides, such as PbSxSe1-x, offer the possibility of room-temperature infrared detection with cut-off wavelengths that may be engineered to fall within the important 3-5 micron mid-wave infrared (MWIR) wavelength range. We present growth and characterization of aqueous spray-deposited thin films of PbSSe. Complexing agents in the aqueous medium discourage unwanted homogeneous reactions so that growth occurs only by heterogeneous reaction on the hydrophilic substrate. The strongly-adherent films are smooth with mirror-like finish. Scanning electron microscopy (SEM) reveals densely packed grains with tens of nm dimensions. Cross-sectional SEM, contact profilometry, and infrared ellipsometry reveal ~500 nm thickness. Measured optical constants reveal absorption out to at least 4.5 micron wavelength and a ~0.3 eV bandgap intermediate between those of PbS and PbSe. Hot probe analysis shows that the films are p-type, and resistivity is found to be ~1 and 40 Ohm-cm at 300 and 80 K, respectively, which confirms semiconducting behavior. Anti-symmetric out-of-plane X-ray diffraction shows sharp peaks that are confidently identified as Clausthalite-Galena solid-state solution. The lattice constant of 6.033 Angstrom indicates an even mixture of PbS and PbSe. Photoconductive response is observed at both nitrogen and room temperature up to at least 1.6 kHz chopping frequency.
3:00 PM - *EM10.12.04
Effect of Alkali Elements on the Solution-Processed Kesterite Solar Cells
Stephan Hass 1 , Christian Anders 1 , Yaroslav Romanyuk 1 , Ayodhya Tiwari 1
1 , Empa-Swiss Federal Laboratories for Materials Science and Technology, Duebendorf Switzerland
Show Abstract
The talk will review the latest findings on how and to what extent the addition of alkali elements can boost the performance of Cu2ZnSn(S,Se)4 (CZTSSe - kesterite) solar cells. Based on a comprehensive experimental series with more than 700 devices containing Li, Na, K, Rb, or Cs as impurity elements, we observe several general trends on how alkali elements influence the morphology and composition of kesterite absorbers, and demonstrate that for each alkali element there is an optimum absorber composition yielding maximum device performance.
3:30 PM - EM10.12.05
Copper Antimony Sulfide—Nanomaterials, Thin Films and Solar Cells
Joel van Embden 1 , Enrico Della Gaspera 1 , Anthony Chesman 3 , Jacek Jasieniak 2
1 Applied Chemistry, RMIT University, Melbourne, Victoria, Australia, 3 Manufacturing, CSIRO, Melbourne, Victoria, Australia, 2 Engineering, Monash University, Melbourne, Victoria, Australia
Show AbstractSolution processing is a low-cost, effective means to produce thin films for photovoltaic (PV) devices. In an effort to find new materials with properties appropriate for PV devices, the exploration of (nano)materials has recently expanded to include copper antimony sulfide (CAS) semiconductors. The dominant phases of CAS are tetrahedrite (Cu12Sb4S13), famatanite (Cu3SbS4), and chalcostibite (CuSbS2). All these phases are p-type semiconductors with high absorption coefficients (~104–105 cm-1), and direct bulk band gaps that vary between ∼1–1.8 eV, which makes them ideal candidates as solar absorber layers in PV devices.
This talk provides an overview of recent work on copper antimony sulfide (CAS) nanocrystals (NCs) and thin films. Beginning from the first reported synthesis of a CAS nanomaterial,[1] the synthetic conditions required to produce CAS NCs and CAS thin films of various phases is presented alongside comprehensive characterization data.[2]
Preliminary data on CuSbS2 thin film solar cell devices is also presented.[3] A facile method to achieve semiconductor thin films of CuSbS2 with micrometer-sized grains under inert atmospheres at mild annealing temperatures is presented. This is achieved through the decomposition of Cu and Sb dithiocarbamate molecular precursors. Through careful optimization of the processing conditions phase pure p-type CuSbS2 thin films with high photoconductivity and large grain sizes may be achieved. These thin films have been incorporated into planar solar cells with a champion power conversion efficiency of 1.04%. These preliminary results establish a platform for achieving higher efficiency devices upon further optimization.
[1] van Embden, J.; Tachibana, Y. “Synthesis and Characterisation of Famatinite copper antimony sulfide Nanocrystals” J. Mater. Chem. 2012, 22 (23), 11466-11469
[2] van Embden, J.; Latham, K.; Duffy, N.W.; Tachibana, Y. “Near-infrared absorbing Cu12Sb4S13 and Cu3SbS4 Nanocrystals: Synthesis, Characterization, and Photo-electrochemistry” J. Am. Chem. Soc., 2013, 135 (31), 11562-11571.
[3] van Embden, J.; Della Gaspera, E.; Chesman, A.S.R.; Jasieniak, J.J. “CuSbS2 Thin Films and Solar cells from Dithiocarbamate Molecular Precursors” (submitted).
3:45 PM - *EM10.12.06
Solution Based Approaches for Earth Abundant Kesterite Thin-Film Photovoltaic Technologies
Edgardo Saucedo 1 , Jacob Andrade-Arvizu 1 , Yudania Sanchez 1 , Marcel Placidi 1 , Victor Izquierdo 1 , Alejandro Perez-Rodriguez 1 2
1 , IREC, Barcelona Spain, 2 IN2UB, Universitat de Barcelona, Barcelona Spain
Show AbstractAvailability of cost-efficient technologies for mass deployment of photovoltaic energy is becoming an urgent issue. A relevant feature to ensure the long term competitiveness of these technologies is related to the use of materials based on earth abundant elements and using sustainable non-vacuum processes that have a higher potential for reduction of production costs. In this sense, during the last years there has been an increased interest in studying new photovoltaic absorbers based on earth abundant elements with high stability and low toxicity, where kesterites (Cu2ZnSn(S,Se)4, CZTSSe) has become one of the most relevant candidates. This family of materials has achieved a promising record conversion efficiency of about 13% at laboratory scale, but additional efforts are still required to push up this value towards the efficiencies currently obtained with more mature thin film technologies. Additionally, the implementation of these technologies using solution-based processes can bring a clear advantage for further reduction of the production costs. Availability of cheap, earth abundant, stable and non-toxic photovoltaic materials allowing the achievement of high efficiency devices produced by sustainable low cost solution-processed routes could revolutionize our energy production schema. In this presentation, the implementation of specific solution-process approaches for boosting the efficiency of kesterite thin film photovoltaic devices efficiency will be reviewed. This includes strategies that are being developed in the frame of the European Project STARCELL (H2020-NMBP-03-2016-720907, www.starcell.eu), and involves the synthesis and doping/alloying of kesterite absorbers by different solution-processed techniques (printing, spray, spin-coating), as well as the identification and implementation of different chemical routes for the deposition of the buffer and window layers. Solution-process strategies are also being developed for the passivation of the different interfaces, aiming to the reduction of interface recombination losses in the devices. Finally, the weaknesses, strengths, and challenges for the implementation of these solution-process approaches in the photovoltaic industry will be discussed.
4:15 PM - EM10.12.07
Selenium-Iodide as Liquid Semiconductor
John Murphy 1 , Lars Voss 1 , Clint Frye 1 , Qinghui Shao 1 , Mark Stoyer 1 , Roger Henderson 1 , Rebecca Nikolic 1
1 , Lawrence Livermore National Lab, Livermore, California, United States
Show AbstractA near room-temperature liquid semiconductor is an attractive candidate material for devices in radiation-harsh environments as it may not suffer performance degradation due to lattice damage. Pure selenium is an elemental liquid semiconductor with a melting point is 220 °C. Having a close to room-temperature melting point is desirable. The selenium-iodide system forms a fully miscible mixture with a melting temperature of 57 °C at the eutectic point near 50 at. % Se; however, there are few reports in the literature on the electrical properties of this system. In this work, we evaluate selenium-iodide as a solid and liquid semiconductor material and the effect of contact materials on the performance of a heterojunction diode. We have fabricated vertical heterojunction diodes from 50:50 at.% Se:I liquid solution and demonstrated power output in the liquid state using UV-light illumination. The diodes were fabricated with a conductive ITO on glass substrate, an SU-8 well to contain the Se:I mixture, and an n-type GaN electrode on sapphire. The devices generated power under UV-illumination during testing from room temperature up to 80 oC , with an open circuit voltage of up to 370 mV and output powers from 5-10 µW. No sudden change in behavior was noted in the transition from solid to liquid. Based on the increase in reverse leakage current with temperature, the bandgap was estimated as 1.64 eV. This value closely corresponds to the absorption band edge measured using UV-Vis spectroscopy of 1.65 eV. Both of these values are fairly close to the bandgap found for gray selenium in the literature of 1.7-1.8 eV. Finite-element drift-diffusion simulations (Silvaco) were performed to study the effect on the open-circuit voltage of the diodes as the work function of the ITO was varied, as well as when the ITO electrode was replaced with p-type 4H-SiC. It was found that the open-circuit voltage of the device should be significantly improved by replacing the ITO electrode with a p-type SiC electrode, increasing the theoretical Voc from 400 to 1050 mV. SiC/Se:I/GaN diodes were then fabricated in a similar fashion using an SU-8 well, and the open circuit voltage under UV-illumination was increased from 370 mV with ITO to 800 mV using SiC, in close agreement with simulation. Further work is needed to study the electrical properties of this system as the concentration of its constituents is varied, to improve the encapsulation of the devices, and to study the stability of these devices as the liquid Se:I semiconductor is exposed to ionizing radiation.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, LLNL-ABS-732950. This support does not constitute an express or implied endorsement on the part of the Government.