Paddy K. L. Chan, The University of Hong Kong
Oana Jurchescu, Wake Forest University
Ioannis Kymissis, Columbia University
Brendan T. O'Connor, North Carolina State University
BB2: Systems and Integration
Monday PM, November 30, 2015
Hynes, Level 2, Room 203
2:30 AM - *BB2.01
Stretchable and Ultraflexible Electronics for E-Textile and Wearable Devices
Takao Someya 1 Naoji Matsuhisa 1 Tsuyoshi Sekitani 1 2 Tomoyuki Yokota 1
1University of Tokyo Tokyo Japan2Osaka University Osaka JapanShow Abstract
The attractiveness of e-textile and wearable devices are their ease in collecting biological information in day-to-day lives and exercises. However, even with conductive fibers or threads, the conventional weaving method was not good enough to pattern fine electrodes and wires. This is why more simplified process, such as printing, to directly pattern durable and conductive materials on a fabric was widely awaited. We have developed novel ink that functions electronically, and succeeded in printing through one printing process a tough elastic conductor. This printable conductor keeps its high conductivity even when it is expanded more than 3 times in size. We printed elastic wires and electrodes with this ink on a fabric and achieved a textile electromyograph sensor. This easy to print textile bio-info sensor can be used in sports, healthcare and medicine.
3:00 AM - BB2.02
Large Area Organic Temperature Sensor Array: From Thermal Conductivity Measurements to Device Fabrication
Paddy K. L. Chan 1 Xiaochen Ren 1 Xinyu Wang 1
1Univ of Hong Kong Hong Kong Hong KongShow Abstract
In organic/metal hybrid materials, the thermal boundary conductance across the metal/organic interface plays a significant role in overall thermal conductivity of the film. The conductivity of the organic or hybrid thin film not only plays a critical role in the thermal stability of the organic devices, but also governs the heat transfer mechanisms. Here by embedding metal nanoparticles into organic semiconductor, we have successively developed a thermistor for direct temperature sensing. By integrating the thermistor with the active matrix organic transistor array, we fabricated a large area 16 × 16 temperature sensor which can be directly used for temperature mapping of objects with various shape. Simultaneously, we apply 3-omega; method to measure the effective conductivity of the thin film and the results are compared with the finite element modeling. By carefully controlling the concentration of the silver nanoparticles, we can modify the sensitivity of different temperature sensors. For a thin layer of Ag and intermixed with DNTT (10% volume ratio), the thermal conductivity decrease from 0.363W/m-K (pure DNTT) to 0.305W/m-K which shows the importance of the thermal boundary conductance. In the integrated temperature sensor array, the hyrbid thermistors are connected in series to the drain contacts and the whole array is developed on flexible substrate. By optimizing the anodization growth of the alumium oxide (AlOx) dielectric, the tempearture array can be powered under 5V with dynamic range higher than 10 bits, which clealy shows their capability in portable temperature sensing applications. The low voltage flexible thermal sensor array is suitable for portable electronic devices and potentially scale up for electronic skin applications. Other application directions such as health monitoring or use as surgery tools can be achieved.
3:15 AM - BB2.03
High Detectivity All-Printed Organic Photodiodes
Adrien Pierre 1 Igal Deckman 1 Pierre Balthazar Lechene 1 Ana Claudia Arias 1
1Univ of California-Berkeley Berkeley United StatesShow Abstract
Photodiodes with high specific detectivity, which entails high external quantum efficiency (EQE) and low dark current, and large pixel sizes enable optical systems capable of imaging lower light intensities. Additionally, the ability of a photodiode to operate under high electric fields at reverse bias increases the amount of photogenerated charge that may be capacitively stored during a single integration period, which is known as the well capacity. Using only the highly scalable printing techniques of blade coating and screen printing to deposit the layers on plastic, flexible organic photodiode arrays are reported with average specific detectivities of 3.45×1013 cmmiddot;Hz0.5middot;W-1 at a bias of -5 V. Polyethylenimine is blade coated over PEDOT:PSS to form the bottom cathode on these inverted devices, which exhibits excellent uniformity in work function modification on the microscale (20 meV standard deviation) as well as over centimetric areas. Furthermore, it is found that the polyethylenimine interlayer is not only essentially for lowering the work function of the electrode to increase EQE but also serves as a hole blocking layer to decrease the dark current density to an average of 150 pA/cm2. Photodiodes fabricated with a screen printed PEDOT:PSS top anode exhibit dark current shunt resistances an order of magnitude higher than devices fabricated using thermally evaporated top electrodes as a result of the creation of defects in the active layer which serve as leakage paths. This results in a lower dark current at high reverse biases for devices with a screen printed top anode than the devices with thermally evaporated metal electrodes. Additionally, these devices show excellent bias stress stability under high applied fields (88 kV/cm) and low variability, with a coefficient of variation of 15% in specific detectivity for 24 pixels across an array with perfect yield. Integration of these photodiodes with organic thin film transistor arrays and charge integrators will also be demonstrated.
3:30 AM - BB2.04
Hierarchical Photonic Surfaces Using Template Stripping of Colloidal Quantum Dot Films
Ferry Prins 1 David K. Kim 1 Eva De Leo 1 Kevin McPeak 1 David J. Norris 1
1ETH Zurich Zurich SwitzerlandShow Abstract
Colloidal quantum dots are highly versatile optoelectronic components that combine size- and shape-tunable properties with the attractiveness of cost-effective solution-phase processing. As such, they are ideal building blocks for the formation of artificial solids in which the colloidal assembly profits from the carefully engineered properties of the individual quantum dots. A variety of quantum-dot-based optoelectronic devices have been reported recently, including light-emitting diodes1 and lasers with tunable emission across the entire visible range,2 as well as demonstrations of efficient solar cells3 and photodetectors.4 It is interesting to consider complementing the nanoscale-structure of the quantum dot assembly with wavelength-scale patterning. This would allow for the creation of hierarchical photonic structures.
Here, we present a template stripping technique that allows for high-resolution wafer-scale patterning of colloidal quantum-dot films.5 We combine simple drop-casting of colloidal dispersions with template stripping using hard silicon templates with lithographically defined patterns. Using this technique, large-area patterns of arbitrary shapes can be transferred with high fidelity onto the quantum-dot film itself. We will show that carefully designed photonic patterns can significantly modify the optical properties of these films, yielding enhanced outcoupling of fluorescence and improved absorption of irradiation. Our technique is compatible with commonly used ligand-exchange strategies for improved electronic properties and can potentially be applied to other solution processable materials such as metallic nanoparticles or organic polymers.
We will discuss the significant improvements that patterned quantum-dot films can offer in the performance of light emitting and light harvesting optoelectronic devices.
(1) Mashford, B. S. et al. Nat. Photonics2013, 7, 407-412.
(2) Dang, C. et al. Nat. Nanotechnol.2012, 7, 335-339.
(3) Chuang, C.-H. M. et al. Nat. Mater.2014, 13, 796-801.
(4) Konstantatos, G. et al. Nature2006, 442, 180-183.
(5) Prins, F. et al. in preparation2015.
3:45 AM - BB2.05
Highly-Aligned, Invisible, Printed Ag Nanofiber Electrode Array
Yeongjun Lee 1 Sung-Yong Min 1 Su-Hun Jeong 1 Tae-Sik Kim 1 Juyeon Won 2 Hobeom Kim 1 Jae Kyeong Jeong 2 Tae-Woo Lee 1
1POSTECH Pohang Korea (the Republic of)2Inha University Incheon Korea (the Republic of)Show Abstract
Ag nanowires (AgNWs) have low sheet resistance and high optical transmittance and are therefore good candidates for use as an alternative to conventional transparent indium-tin-oxide (ITO) electrodes. However, use of conventional short AgNWs has allowed fabrication of only randomly-dispersed sheet-type transparent electrodes, so the approach it cannot take full advantage of nano-sized electrodes (nanoelectrode). Moreover, the conventional solution-dispersed AgNWs have the limitations such as low dispersion uniformity, poor surface roughness, high optical haze and low controllability, which should be resolved. Here, we report use of Electrohydrodynamic Nanowire Printing (ENP) as a simple, fast and inexpensive method to print Ag nanofibers (Ag NFs) for use as transparent electrode. ENP produces highly-aligned and individually position-controllable Ag NFs with average diameter of 695 nm and low resistivity ρ = 5.7 µOmega;#8729;cm, which is comparable with that of bulk Ag (ρ = 1.6 µOmega;#8729;cm). We fabricated various FETs including all-NF FETs (carrier mobility ~ 2.08 cm2middot;V-1middot;s-1) that use two strings of Ag NFs, one as a nano-sized source nanoelectrode and one as a drain nanoelectrode. We also demonstrated organic light emitting diodes (OLEDs), transparent heaters and touch screen panels, thereby proving the feasibility using of printed Ag NF transparent electrodes. ENP will be useful for fabrication of various kinds of future nanoelectronics.
4:30 AM - *BB2.06
High Performance Digitally Printed Electronic Systems
Gregory Lewis Whiting 1 David Schwartz 1 Tse Nga Ng 1 Ping Mei 1 Brent Krusor 1 Eugene Chow 1 JengPing Lu 1
1Palo Alto Research Center Palo Alto United StatesShow Abstract
Through the use of digital printing methods, custom electronic systems can be additively fabricated in an on-demand fashion. Many device types (logic circuits, sensors, memory, power sources, etc) can be printed entirely from solution-based inks of conductors, semiconductors, dielectrics and stimuli-responsive materials. However, all-printed systems incorporating these devices are often constrained in the appliations they can address by the performance of the printed circuits, which are typically limited by print resolution and materials properties. In order to best take advantage of the assortment of printed components available a hybrid approach that incorporates low-profile Si-CMOS components into the printed system can be used to provide a balance between electrical and mechanial performance, customizability and cost. Following this approach, examples of digitally fabricated hybrid electronic systems for wireless multimodal sensing will be described as will approaches for providing power to these distributed systems. Additionally, a print-like method of programmable micro-assembly to directly transport and orient large numbers of pre-fabricated silicon chips using electrostatic fields will also be discussed.
5:00 AM - BB2.07
Solution-Processed Radio Frequency Diodes Based on Co-Planar Asymmetric Nanogap Electrode Architectures
James Semple 1 Stephan Rossbauer 1 Dimitra Georgiadou 1 Thomas Anthopoulos 1
1Imperial College London London United KingdomShow Abstract
Envisaged as key enablers of molecular electronics, plasmonic and spintronic devices, nanogaop electrodes have become a growing area of research in recent years. Many routes towards such structures have been investigated, including mechanical break junctions, electromigration, oblique-angle shadow evaporation and electron beam lithography. However, such nanofabrication processes suffer from low throughput, poor scalability and multiple complex processing steps. Furthermore few of these methods can be readily applied to produce nanogaps between dissimilar electrodes, hence closing the door to the fabrication of devices that rely on ambipolar carrier injection (e.g. light-emitting diodes) or extraction (solar cells, photodetectors etc.).
Here, we present a unique technique, namely adhesion lithography (a-Lith), capable of fabricating such asymmetric nanogap structures, and doing so at an unprecedentedly large scale1. The process relies on the selective tuning of electrode surface energies using self-assembled monolayers (SAMs) and the application of adhesive forces. The bulk of the process is done via solution and features on the order of 10 nm with aspect ratios of over 106 have been demonstrated.
One such application of this structure is the co-planar nano-Schottky diode. The latter type of diodes may be fabricated by a single step deposition of the semiconductor material directly onto the nanogap electrode structures. The mismatch between electrode work functions allows current flow in one direction only, the small active area reduces device resistance, while the planar structure minimises device geometric capacitance. Thus we demonstrate devices with extremely high rectification ratio (>106) and minimal RC constants due to the co-planar device architecture. The result is the demonstration of nano-Schottky diode operating at radio frequencies (>20 MHz) while they can be made using various semiconductors, including low temperature (<200°C) solution processed ZnO as well as solution deposited C60. Such large-area, low-cost devices could be the ideal candidate for integration into printable RFID tags, and enablers of future technologies such as widespread RFID supply chain management and the Internet of Things.
1. Beesley, D. J.; Semple, J.; Jagadamma, L. K.; Amassian, A.; McLachlan, M. A.; Anthopoulos, T. D. Nature communications 2014, 5.
5:15 AM - BB2.08
Direct Printing of Sub-10mu;m Metallic Features Using Engineered Nanoporous Stamps
Sanha Kim 1 Hossein Sojoudi 1 2 Hangbo Zhao 1 Gareth McKinley 1 Karen Gleason 2 A. John Hart 1
1Massachusetts Institute of Technology Cambridge United States2Massachusetts Institute of Technology Cambridge United StatesShow Abstract
Direct printing of conductive inks made from metallic nanoparticles is an attractive approach for scalable low-cost manufacturing of flexible electronics, such as thin film transistors and transparent electrodes for organic displays and solar cells. Accordingly, the traditional methods including screen, gravure, offset, flexography, and inkjet printing have significant commercial uses. Although each method has its own characteristics and advantages, the common limitation in device fabrication is the printing resolution, limited to smallest feature size of approximately 20 mu;m. In case of flexography, the solid elastomeric stamps load a thin layer of ink on the top surfaces of the stamp features, which is prone to film instability and liquid spreading as feature size becomes smaller. For emerging applications of printed electronics such as high-resolution flexible displays or metal grid transparent electrodes, it is necessary to print conductive patterns in 1-10 mu;m size range.
We have developed a nanoporous stamp material enabling direct printing of electronic materials with micron-scale resolution. The stamps comprise vertically aligned carbon nanotubes (CNT “forests”) coated with poly(perfluorodecyl acrylate), (pPFDA), via initiated chemical vapor deposition. The stamp structures have high porosity (>90%), possess structural robustness against capillary forces upon liquid infiltration/evaporation, and are sufficiently compliant (elastic modulus of ~30 MPa) for conformal contact against the target substrate. For printing, the nanoporous stamps are used in the same way as the solid elastomeric stamps in flexography, as the ink is transferred from compliant and raised stamp structures to the target substrate via local contact. However, the high porosity of the new stamp allows the ink to be confined inside the microstructures. As a result, upon contact with the target substrate, ink is transferred locally via the porous surface, realizing excellent replication of stamp pattern with uniform thickness. Using the engineered CNT stamps, we demonstrate scalable patterning of silver nanoparticles approaching micrometer dimensions with high fidelity (e.g. sharp corner radius ~3 mu;m, fine edge roughness <1 mu;m, and uniform thickness <100 nm). After sintering, the silver patterns show maximum conductivity of ~4.0×107 S/m (~60% of bulk silver). Printed silver honeycomb patterns, with minimum linewidth of 3 mu;m, are also directly fabricated on glass plate and PET films. After annealing, this pattern exhibits ~89% transmission at 200-800 nm wavelength with 6.4-13.1 Omega;/#9633; sheet resistance, which is significantly lower than ITO (20-100 Omega;/#9633; over 80% transparency). We further discuss the contact and fluid mechanics of ink transfer, and analyze the potential for continuous operation of nanoporous stamps for micron-scale patterning at high speed (~m/s) which would overcome the mutual limitations of existing patterning methods for manufacturing of printed electronics.
5:30 AM - BB2.09
Printing Organic Semiconductors for Logic Circuits with Low Patterning Errors and Electrical Variability
Gaurav Giri 1 Steve Jeung Hoon Park 2 Zhenan Bao 3
1MIT Cambridge United States2Columbia University New York United States3Stanford University Stanford United StatesShow Abstract
Logic circuits are necessary to fulfill the vision of low cost, large area organic electronics, made with organic semiconductors (OSC) as the charge transfer layer. However, these circuits have stringent requirements. Primarily, all the thin film transistors (TFTs) participating in the circuit need to have a low variation in charge transfer characteristics (charge carrier mobility, threshold voltage, current, etc.). Additionally, organic circuits should be operated with low power consumption. To this end, research is being performed to pattern OSCs on the organic circuit to reduce parasitic current leakage. These twin requirements of low variability and OSC patterning set up conflicting goals, as the variability increases if each TFT is patterned individually. Moreover, patterning TFTs such that every TFT works, for the numerous TFTs required for logic circuits, is difficult with conventional methods such as ink jet printing due to patterning errors over large areas.
Here, we show a self-patterning method that does not require an extra patterning step to deposit the OSC layer onto the organic circuit. We have developed a surface functionalization procedure for a variety of oxide and metal surfaces, which, when paired with controlled solvent flow, can pattern OSCs in the TFT channel region only. Using this method, we show 100% viability of the patterned TFTs with low variability of charge carrier mobility and current. This method has been used to form logic gates and other organic circuits.
5:45 AM - BB2.10
High Mobility Low-Voltage Organic Transistors and Unipolar and Complementary Ring Oscillators on Plastic and Paper Substrates
Ulrike Kraft 1 2 Kazuo Takimiya 3 Florian Letzkus 4 Tarek Zaki 4 Joachim Burghartz 4 Edwin Weber 2 Hagen Klauk 1
1Max Planck Institute for Solid State Research Stuttgart Germany2TU Bergakademie Freiberg Freiberg Germany3RIKEN Advanced Science Institute Wako, Saitama Japan4Institute for Microelectronics (IMS Chips) Stuttgart GermanyShow Abstract
Potential applications of organic thin-film transistors (TFTs) are flexible displays, and the addition of active electronic anti-counterfeiting and tracking features to the existing passive security features on banknotes. For these applications, certain requirements such as low-voltage operation, a good shelf-life stability and high switching speeds have to be fulfilled not only on smooth Si wafers substrates used for material screenings but also on realistic plastic and paper substrates.
In this work, the low-voltage operation of the TFTs was enabled by employing a very thin hybrid gate dielectric consisting of a thin AlOx layer and a self-assembled monolayer of either an alkylphosphonic acid or a fluoroalkyphosphonic. The small thickness of the gate dielectrics leads to a large gate-dielectric capacitance and therefore allows operating voltages below 3V.
The utilized small-molecule semiconductors DNTT and its derivatives C10-DNTT and DPh-DNTT provide large carrier mobilities and an excellent air stability.
However, a good dynamic performance can be accomplished only by minimizing the parasitic capacitances, i.e., by employing TFTs with small lateral dimensions. In this work TFTs with channel lengths (L) ranging from 100µm down to 0.5µm were fabricated using high-resolution silicon stencil masks[3,4] that allow the accurate patterning of organic TFTs with small dimensions and an excellent parameter uniformity.
For DPh-DNTT TFTs on plastic substrates, carrier mobilities of 2.4cm2/Vs (L=100µm) and 0.6cm2/Vs (L=1µm) were measured. To test the suitability of the TFTs for real applications, we fabricated 11-stage unipolar and complementary ring oscillators on plastic substrates and on a 5-Euro banknote. For DPh#8209;DNTT TFTs with L=1µm on the plastic substrates, a signal delay per stage of 240ns was measured in ambient air at a supply voltage of 4V, which is the smallest signal delay reported to date for organic TFTs on flexible plastic substrates at operating voltages below 10V. For complementary circuits with p-channel DPh-DNTT TFTs and n#8209;channel PTCDI-(CN)2-(CH2C3F7)2 TFTs, the stage delay at 5V was as short as 3.1mu;s.
Despite the rough fibrous surface of the banknotes, the TFTs have mobilities up to 1.2cm2/Vs (p-channel TFTs) and 0.17cm2/Vs (n#8209;channel TFTs). The latter value is among the largest reported for organic n-channel TFTs on paper substrates. The thin gate dielectric allows the bending of the devices and in our tests no significant influence on the carrier mobility and the gate current was observed.. At 4 V, the measured stage delays are 2.5µs (unipolar) and 10µs (complementary). In comparison to earlier reports on organic circuits on paper substrates, these ring oscillators operate faster and at lower voltages.
 U. Kraft et al., Adv. Mater., 2015, 27, 207
 U. Kraft et al., DRC, Santa Barbara, USA, 2014,
 F. Ante et al., Small, 2012, 8, 73
 F. Letzkus et al., Microelectron. Eng., 2000, 53, 609
Monday AM, November 30, 2015
Hynes, Level 2, Room 203
9:00 AM - *BB1.01
Oxide and Organic TFTs on Thin Solution Cast Polymeric Substrates
Thomas N. Jackson 1
1Pennsylvania State Univ University Park United StatesShow Abstract
Flexible electronics has been demonstrated using both organic and inorganic semiconductors on a variety of substrates and using a wide range of fabrication approaches. Roll-to-roll processing has gained interest for high-throughput manufacturing, but presents challenges for in vacuum deposition, photolithography, and alignment between layers, complicated by substrate flatness and dimensional stability issues. Flexible substrates laminated onto rigid carriers (usually glass or Si) allow device fabrication using more standard equipment and processes, but often only partially solves substrate flatness and dimensional stability problems. We have used few micron thick polyimide layers solution-cast and cured on rigid glass or Si carriers to fabricate thin film transistors on flexible substrates. The thin polyimide layers reproduce the carrier flatness and typically have few nm surface roughness. Dimensional stability for small (few cm) substrates is excellent with only few ppm level distortion after processing steps including heating to 200 °C, photolithography (including exposure to organic solvents), and vacuum deposition. At the completion of device processing the thin flexible substrate can be released from the substrate by etching a sacrificial layer or by simple mechanical stripping. Thin solution-cast flexible substrates also provide advantages for applications that require small bending radius. Ignoring effects from device and other added layers, strain is proportional to substrate thickness. Thin substrates allow smaller bending radius than thicker substrates before the strain level that results in device and interconnect degradation is reached. Oxide semiconductor n-channel TFTs integrated with organic p-channel TFTs provide a simple complementary circuit technology. ZnO thin film transistors fabricated on thin solution-cast polyimide substrates have characteristics very similar to devices fabricated on glass. Substrates released by mechanical stripping were flexed 50,000 times with only small changes in device characteristics. Solution cast polymeric substrates provide a simple path to flexible active electronics.
1. Y. V. Li, D. A. Mourey, M. A. Loth, D. A. Zhao, J. E. Anthony, and T. N. Jackson, “Hybrid Inorganic/Organic Complementary Circuits using PEALD ZnO and Ink-Jet Printed DiF-TESADT TFTs,” Organic Electronics, 14, pp. 2411-7 (October 2013).
2. H. Li and T. N. Jackson, “Oxide Semiconductor Thin Film Transistors on Thin Solution-Cast Flexible Substrates,” IEEE Electron Device Letters, 33, pp. 35-37 (January 2015).
BB3: Poster Session I
Monday PM, November 30, 2015
Hynes, Level 1, Hall B
9:00 AM - BB3.01
Orthogonal Hydrofluoroethers Enable Photo-Patterning of State-of-the-Art Phosphorescent Small Molecule OLEDs and Deposition of Outcoupling Enhancement Structures
Simonas Krotkus 2 Tim Schaefer 2 Tobias Schwab 2 Fabian Ventsch 2 Daniel Kasemann 2 Alexander A. Zakhidov 2 Simone Lenk 2 Karl Leo 2 Malte C Gather 2 1
1University of St Andrews St Andrews United Kingdom2Technische Universitauml;t Dresden Dresden GermanyShow Abstract
After nearly three decades of thorough development, small molecule organic light emitting diodes (OLEDs) have reached a point where their operational lifetimes are now compatible with the requirements in a range of commercial applications (in particular by the flat panel display industry). However, from a fabrication point of view, one of the main drawbacks of the technology remains its incompatibility with many solution based processes. Any exposure of devices to water or organic solvents tends to degrade device performance and frequently has catastrophic impact on device lifetime. This prevents the use of photolithography - widely used in the CMOS and PCB industry - for the fabrication of full-color OLED displays and renders packaging and lamination of OLEDs challenging.
Hydrofluoroethers (HFE) have been proposed as an orthogonal material system which can be brought in contact with OLEDs and other organic devices without damaging the material. Here, we show that HFE based solvents enable patterning of state-of-the-art phosphorescent OLEDs by a photolithographic lift-off process without any impact on device efficiency or device lifetime. For devices exposed to our HFE process, the extrapolated t0.75 lifetime at an initial luminance of 500 cd m#8209;2 remains at over 100,000 h.
Using a similar concept we have also found that HFE polymers allow solution based deposition of additional layers on top of fully functioning OLEDs. This may prove useful in a range of scenarios e.g. as initial barrier layers in thin-film encapsulation, for mechanical balancing in flexible devices, hellip; . Here, we study ways of enhancing the efficiency of light extraction by depositing HFE polymers loaded with high-refractive index nanoparticles onto top-emitting OLEDs. We find that the outcoupling efficiency of white top-emitting OLEDs is enhanced by 1.5 to 2.3 fold using this approach and that their angular emission characteristics, i.e. the change in color with viewing angle, is also greatly improved.
 S. Krotkus, F. Ventsch , D. Kasemann, A. A. Zakhidov, S. Hofmann , K. Leo, M. C. Gather, “Photo-patterning of Highly Efficient State-of-the-Art Phosphorescent OLEDs Using Orthogonal Hydrofluoroethers”, Adv. Optical Mater.2, 1043 (2014)
 T. Schaefer, T. Schwab, S. Lenk, M. C. Gather, “White top-emitting OLEDs with solution-processed nano-particle scattering layers”, submitted
9:00 AM - BB3.02
New Organic/Inorganic Hybrid Films for Lighting Applications
Sara El Hanbali 1 Jennifer Weimmerskirch-Aubatin 2 Christophe Labbe 2 Nathalie Bar 3 Didier Villemin 3 Nicolas Barrier 1 Alain Pautrat 1 Ulrike Lueders 1 Vincent Caignaert 1 Olivier Perez 1 Sophie Boudin 1
1CRISMAT, CNRS/ENSICAEN/UCBN Caen France2CIMAP, CNRS/CEA/ENSICAEN/UCBN Caen France3LCMT, CNRS/ENSICAEN/UCBN Caen FranceShow Abstract
Nowadays there are many applications for optoelectronic films as solar cells, photodetectors or LEDs. Currently, the most common materials for commercial devices are either organic or inorganic. However since few years optoelectronic organic/inorganic hybrid films are also studied. The latter ones can provide durability and intermediate costs between organic or inorganic films. Recently, photoconducting hybrid films were electrodeposited by an auto-assemblage of an inorganic ZnO semi-conducting network and an organic network of light absorbing and conducting 3-methylquinquethiophene dicarboxylic acid molecules1. In this context, we explored systems to generate new hybrid films for light emission by similar electrodeposition techniques. We will present here results on new photoluminescent ZnO / naphthoate hybrid films.
Prior to electrodeposition synthesis, the ZnO / naphthoate system was investigated by solution and hydrothermal synthesis. A new ZnO / naphthoate hybrid phase denoted H1 was isolated, the crystal structure was determined by single crystal X-Ray diffraction and thermal stability by thermogravimetric analysis.
Electrosynthesis and deposition of H1 on transparent electrodes were secondly optimized by varying concentration bath, temperature and deposition potential. Purity, quality and crystal structure of films were checked using single crystal structure of H1, the film microstructure was studied by scanning electron microscopy. Transmittance and photoluminescence properties were analyzed by photoluminescence and photoluminescence excitation spectroscopy. The H1 film exhibits a blue emission through UV excitation.
In order to study further electroluminescence properties, devices based on H1 were developed. Since H1 films deposited on transparent electrodes are sparse, embedding by resins to prevent shortings and deposition of metallic back electrodes were optimized. X-Ray diffraction and photoluminescence analysis have been performed on devices to ensure the preservation of H1 hybrid material during successive fabrication steps.
The synthesis of the H1 hybrid phase and its crystal structure, the film electrodeposition and its microstructure, the photoluminescence properties and the device fabrication based on luminescent H1 hybrid films, will be presented.
(1) Sofos, M.; Goldberger, J.; Stone, D. A.; Allen, J. E.; Ma, Q.; Herman, D. J.; Tsai, W.-W.; Lauhon, L. J.; Stupp, S. I. Nat. Mater. 2009, 8 (1), 68-75.
9:00 AM - BB3.03
Transparent Ag-Free OLED Fabricated by OVPD Using Thin Au Contacts
Pascal Pfeiffer 1 Dominik Stuemmler 1 Sofia Loginkin 1 Michael Heuken 1 2 Andrei Vescan 1 Holger Kalisch 1
1RWTH Aachen Univ Aachen Germany2AIXTRON SE Herzogenrath GermanyShow Abstract
A major drawback of Ag-based transparent OLED is a limited lifetime, mostly due to diffusion from the Ag cathode into the organic layers. In this study, a new approach using Ag-free transparent contacts is investigated. A 1 nm Ti precoat and a thin Au anode (8 nm) are deposited on glass substrates suppressing lateral guided modes [Slawinski, M., et al., MRS Proceedings 1627, 2014]. Hole injection is improved by a 2 nm MoOx layer. The organic stack deposited by OVPD (organic vapor phase deposition) is comprised of NPB as HTL, Ir(MDQ)2(acac) doped in a cross-faded NPB/TMM matrix [Lindla, F., et al., Applied Physics Letters 95, 213305, 2009] and Alq3 as ETL. Subsequently, an inorganic electron injection layer (EIL) of 1 nm LiF and 2 nm Al is formed and coated with a thin Au film (16 nm) to constitute the transparent OLED cathode. The active area measures 2 cm2. The OLED are encapsulated with a glass cover without getter package to maintain transparency.
For lifetime comparison, transparent reference OLED with thin Ag films (20 nm) as cathode material on top of the EIL have been fabricated. We will show a 6 fold increase in lifetime (LT50, 4 mA/cm2) from 27 h to 172 h when replacing Ag by Au as cathode material with similar electro-optical characteristics. In wavelength-dependent transmittance measurements, the OLED with Au contacts show an average in transparency of about 30% in the range of VIS-light including absorption and reflection of the glass substrate and cover. In terms of turn-on voltage, all transparent OLED (Ag & Au cathode) feature almost identical values to a standard non-transparent OLED (anode: oxygen plasma activated ITO; cathode: LiF/Al) comprising the same organic stack. This confirms similar charge injection in those devices.
J-V characteristics show a considerable series resistance which we attribute to the different anode design and higher sheet resistance of the thin Au film compared to the thick Al cathode in the standard OLED (20 Omega;/sq to <1 Omega;/sq). J-V-L-measurements reveal a strong influence of substrate temperature during the OVPD process on the current efficacy of the OLED. Optimization of substrate temperature is crucial for good wettability of the substrate by NPB and smooth morphology of the organic layers.
Top-side (cathode) light emission is about 70% of bottom-side (anode) emission measured on an encapsulated OLED. This is owed to the fact that the top Au film is thicker than the bottom Au film due to a somewhat larger roughness to achieve similar sheet resistance. Additional losses are caused by the air gap between the cathode contact and the glass cover.
To further increase lifetime, we are currently working on an inverted transparent OLED structure to bury the reactive LiF/Al EIL turning it less accessible for oxygen and moisture. First results show difficulties in electron injection when depositing Al/LiF below the organic stack which may be attributed to insufficient thermal activation of the EIL.
9:00 AM - BB3.04
Evaporation-Driven Assembly of Nanomaterials in a Confined Cylindrical Geometry
Yong Lin Kong 1 Francois Boulogne 1 Hyoungsoo Kim 1 Janine K. Nunes 1 Jie Feng 1 Howard Stone 1
1Princeton University Princeton United StatesShow Abstract
The ability to assemble nanomaterials, such as quantum dots, could enable the creation of functional devices that present unique optical and electronic properties. For instance, light-emitting diodes with exceptional color purity could be printed via the evaporative-driven assembly of quantum dots. Nevertheless, current studies of the colloidal deposition of quantum dots have been limited to the surfaces of a planar substrate. Here, we investigate the evaporation-driven assembly of quantum dots inside a confined cylindrical geometry. Specifically, we observe distinct deposition, coating patterns and cracks formation of quantum dots at different positions along the length of a capillary tube. Such changes of coating behavior could be influenced by the evaporation speed as well as the concentration of quantum dots. Understanding the factors governing the coating process could provide a means to control the assembly of nanomaterials inside a capillary tube, ultimately enabling the creation of novel electronics devices.
9:00 AM - BB3.05
A Novel Fabrication Method for Passivation of Large-Area OLED Anode Grid Lines
Donald Lupo 1 Marika Janka 1
1Tampere University of Technology Tampere FinlandShow Abstract
Large-area organic light emitting diodes (OLEDs) suffer from inhomogeneous luminance caused by the large lateral voltage drop inside the transparent electrode. To improve the device performance, the conductivity of the transparent electrode is typically increased by integration of metal grids with the transparent electrode. However, these grid lines make the anode and cathode of the device prone to shorting. Shorting of the electrodes can be avoided by applying a passivation layer on the grid lines. The grid as well as the passivation layer decreases the device active area, thus making the accurate alignment of the passivation layer crucial. We have developed a novel Joule heating based self-alignment process for solution-processable polymer insulators to increase the localization of the insulator on the grid lines. [2, 3]
Here, we report passivation of an OLED anode and its implementation in an OLED device. The grid lines were deposited onto an indium tin oxide (ITO) electrode. A cross-linkable polymer dielectric was then patterned using a Joule heating process. The Joule heating enables very precise alignment of the passivation layer with the grid line, and thus optimizes the OLED active area, and it has the potential for cost effective industrial scale production. None of the Joule heating steps require vacuum processes or time consuming and expensive microscale registration.
 K. Neyts, M. Marescaux, A. U. Nieto, A. Elschner, W. Lovenich, K. Fehse, Q. Huang, K. Walzer, and K. Leo. Inhomogeneous luminance in organic light emitting diodes related to electrode resistivity, J. Appl. Phys.,100, 114513 (2006).
 M. Janka, S. Tuukkanen, T. Joutsenoja, and D. Lupo. Self-alignment method for solution-processable dielectric structures via joule heating. Thin Solid Films, 519, 6587 (2011).
 Janka, M., Saukko, E., Raumonen, P., and Lupo, D. Optimization of large-area OLED current distribution grids with self-aligned passivation. Organic Electronics,15, 3431 (2014).
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Controlling Vertical Composition Profile in Organic Photovoltaic Active Layers through the Photoprecursor Approach
Mitsuharu Suzuki 1 Yuji Yamaguchi 2 Ken-ichi Nakayama 2 3 Hiroko Yamada 1 3
1Nara Institute of Science and Technology Ikoma Japan2Yamagata University Yonezawa Japan3CREST, JST Kawaguchi JapanShow Abstract
The active layer of organic photovoltaic cells is typically a mixture of p- and n-type semiconducting materials, and the vertical distribution of these materials has significant impact on the device performance. Along this line, the present contribution shows that the vertical composition profile in photovoltaic active layers can be effectively controlled through a unique solution process which we call “photoprecursor approach”.
The precursor approach enables solution deposition of organic semiconductors by a stepwise process, in which a precursor compound is solution deposited then converted to a target semiconducting material by in-situ chemical conversion. When the solubility of the post-conversion film is low enough, one can construct multi-layer structures by repeating the deposition/conversion cycle. This allows sequential deposition of different materials through solution-based processes, and thus high degree of control over the vertical composition profile in the resulting films.
Among various types of precursor compounds, a-diketone-type photoprecursors of acenes are characterized by the mild reaction conditions for their conversion, where only visible-light irradiation is required. In a previous work, we employed this photochemistry to prepare p-i-n-type photovoltaic active layers based on 2,6-dithienylanthracene (DTA) as p-type material and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as n-type material. The resulting device showed a power-conversion efficiency (PCE) of 1.50%, which was 67% higher than that of the corresponding bulk-heterojunction (BHJ) single-layer structure (0.90%) . We also reported that the PCE could be improved to 2.89% by employing three-component p-i-n films containing another donor 2,6-bis(5'-(2-ethylhexyl)-(2,2'-bithiophen)-5-yl)anthracene (EH-DBTA).
The present report deals with our recent efforts, in which we have improved the PCE to be as high as 4.20%. This was achieved by employing a newly synthesized diketopyrrolopyrrole-anthrathiophene conjugate (AtD2T) as p-type material. The i-layer composed of AtD2T and PC71BM can absorb the whole range of visible light, and AtD2T has an ideal energy level of the highest occupied molecular orbital. These features lead to a relatively high short-circuit current density and open-circuit voltage (9.92 mA cm-2 and 0.89 V, respectively). Importantly, the PCE of the corresponding BHJ device stays as low as ca. 2%, highlighting again the advantage of the p-i-n structure and thus the importance of controlling the vertical composition profile. The presentation will also include the examination of the vertical profile through cross-section scanning-electron microscopy.
 Y. Yamaguchi et al. Sci. Rep.4 (2014), 7151.
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A New Facile Method to Pattern a Conductive Polymer
Namchul Cho 1 Justin Diekhans 1 Malia Steward 1 seungkeun Choi 1
1University of Washington Bothell United StatesShow Abstract
Conductive polymers have been widely used in organic electronic devices such as organic solar cells, thin film transistors, and light emitting diodes because of their unique optical and electrical properties together with excellent flexibility and processability. The fabrication of micropatterned conducting polymer is also an important research area for their practical applications. In order to construct various flexible electronic devices such as neural electrodes and MEMS resonators, patterning the conductive polymers with an accuracy of hundreds of micrometers without decreasing their conductivity are required. To date, several patterning strategies have been reported such as soft-lithography, dip-pen lithography, template-assisted synthesis, photolithography, and electrochemical deposition. These methods are useful but still limited to achieve cost effectiveness, facile pattern design and process, and large-scale fabrication.
In this talk, we will report a facile approach to fabricate a micropatterned conductive polymer (PEDOT:PSS) on a negative photoresist (SU-8). Because the thick conducting polymer was strongly adhered to the patterned SU-8 substrate by covalent bonding, we were able to further deposit thick copper electrodes uniformly on top of it by using electrodeposition. Furthermore, we will show that the free standing conductive polymer on SU-8 can be fabricated by controlling adhesion between SU-8 and glass substrate. This patterned free standing films with the thickness of around 20 micrometers show excellent flexibility and maintain their conductivity after severe bending test.
To make a patterned PEDOT:PSS on a SU-8 thin film, we applied an SU-8 on a glass substrate and exposed it with UV light via a photomask. UV exposed portions of SU-8 were cross-linked during the pose expose baking on a hotplate. We then spin-coated a PEDOT:PSS on top of it. SU-8/PEDOT:PSS films were annealed at 170 °C for 30 minutes and then the films were developed using 1-Methoxy-2-propyl acetate, creating patterned SU-8 structures coated with the PEDOT:PSS. PEDOT:PSS on top of unexposed SU-8 was easily removed during the developing process. We found that the deposited PEDOT:PSS can be linked with remaining epoxide groups on top of cross-linked SU-8 by forming sulfonyl ester. Through this condensation reaction between epoxides in SU-8 and styrene sulfonic acid groups in PEDOT:PSS, the chemically crosslinked micropatterned SU-8 structures coated with PEDOT:PSS are obtained. We further applied this patterned conducting films as a seed layer for electroplating of copper electrodes. The electroplating of copper with a thickness of up to 15 µm was successfully demonstrated. We believe that the patterned microelectrodes on SU-8 substrates can be a promising platform for realization of several practical organic electronics and bioelectronics devices.
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Advanced Polymer Hole-injection and Electron-Injection Layers to Make Ohmic Contacts to Organic Semiconductor Devices
Cindy Guanyu Tang 1 Mervin Ang 1 Kim Kian Choo 1 Peter Ho 1 Rui Qi Png 1 Lay-Lay Chua 1
1National University of Singapore Singapore SingaporeShow Abstract
We report the development of advanced polymer hole-injection and electron-injection layers in collaboration with our industry partner that are now able to provide ohmic hole injection into organic semiconductors with ionization potentials up to 6.0 eV and ohmic electron injection into organic semiconductors with electron affinities down to 3.7 eV. The layers are based on new concepts in p-doped and n-doped polymers that can overcome the challenges of stability and dopant profile migration at these extreme values. We demonstrate novel device architectures including fully-solution-processed inverted organic solar cells without the use of low-workfunction metals, and the first organic CMOS circuit elements based on differentiated electrodes with the p- and n-doped charge-injection layers. This opens new device architectures leading to new possibilities for higher efficiency and performance not accessible previously.
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Aerosol-Jet Printed Flexible Organic Photodiodes
Ralph Eckstein 1 2 Tobias Roedlmeier 1 2 Tobias Glaser 3 2 Sebastian Valouch 1 2 Ralf Mauer 2 Uli Lemmer 1 Gerardo Hernandez-Sosa 1 2
1Karlsruhe Inst of Technology Karlsruhe Germany2InnovationLab Heidelberg Germany3Kirchhoff-Institut fuuml;r Physik Heidelberg GermanyShow Abstract
Organic semiconductors offer very promising and unique properties towards light sensing applications e.g. tunable absorption spectra, solution processability, mechanical flexibility and high internal quantum efficiencies. For that reason, optical sensors using these materials fabricated by industrial relevant printing techniques will become more and more relevant for many applications in e.g. health sensing in wearables and medical diagnostics, environmental monitoring, or automotive industry, and even integrated and customer designed printed electronics. In this work we present highly efficient multi-layer organic photodiodes based on the polymer-fullerene blend PTB7:PC70BM, an AZO electron transport layer, and HC PEDOT:PSS electrodes, which have been entirely aerosol jet printed (AJP) on flexible PET substrates. AJP is a digital printing technique which allows for very precise deposition of a large variety of inks with a feature size down to a few micrometers. We present a comprehensive electrical and optical characterization of the printed layers and devices in dependency of the active layer thicknesses, surface topography and transparency. Devices with specific detectivities of >1E12 Jones over a broad wavelength range (400-750 nm) and maximum responsivities of 0.25 A/W have been prepared.
 R. Eckstein et al. Advanced Electronic Materials. doi: 10.1002/aelm.201500101 (2015)
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High-Throughput Strategy for Concentration and Orientation Optimization of Polymer Thermoelectric Composites Containing In Situ Growth of Secondary Phase Particles
Robert Ireland 1 Howard E. Katz 1
1Johns Hopkins University Baltimore United StatesShow Abstract
We developed a new combinatorial approach to analyze in situ growth of organometallic crystallites within polymer matrices using one-pot solution-processing methods, and to control the distribution of organometallic particles. We controlled the distribution and orientation of particles by exploiting geometric confinement in addition to guiding the direction of solvent evaporation with physical gradients. We visually characterized the morphology using microscopy and measured the Seebeck coefficients and conductivities to compare performances. We show that the optimal additive concentration and distribution can be estimated quickly with the added advantage of comparing properties of parts of a sample that are prepared from the same source under the same conditions.
First we used templated 2D wells of various shapes during drop-casting because the growth direction of secondary phase particles was determined by the evaporation of the solvent or the solidification wave front of the bulk film that both occur from the outside in towards the center (directly observed under microscope by taking pictures over time). For example, using square wells the crystals grow radially inward. Knowing this we can control how crystals grow locally with respect to pre-deposited electrodes, and obtain crystals that orient all perpendicular or all parallel to the electrodes.
Secondly, we used physical gradients to obtain a distribution in morphologies and additive concentration along the entire sample by guiding the direction of solvent evaporation. This was achieved using elongated wells (rectangles) and by imposing a gradient along the length, suitable for high-throughput screening to quickly find optimal composite compositions or to test ranges in the special distribution of second phases. Without the gradient we obtain homogenous morphology and concentration along the sample, but having radial orientation of crystals due to evaporation ending at the film center.
Temperature gradients resulted in a greater range in distribution of particle concentrations across the sample, but their orientation was mostly random. Samples that were sloped slightly (i.e. gravitational gradient) showed greater uniform macroscopic order and differed less over the length of the sample, with crystals that grow predominately in the direction of solvent evaporation. The bulk films solidify first at either the hot side or the top of the slope, resulting in the lowest concentration of second phase component in that region due to zone refinement and smaller particle dimensions due to film thinning. A combination of the two gradients provides the ultimate range of both composition and morphology in single samples.
The inorganic material work and electrical measurements were supported by the National Science Foundation, Division of Materials Research, Grant Number 1005398. Polymer synthesis was supported by the Department of Energy, Office of Basic Energy Sciences, Grant Number DE-FG02-07ER46465.
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Gas Permeation Barriers Prepared by Spatial Plasma Enhanced ALD at Atmospheric Pressure
Lukas Hoffmann 1 Detlef Theirich 1 Sven Pack 1 Tim Hasselmann 1 Daniel Schlamm 1 Andre Raeupke 1 Thomas Riedl 1
1Chair of Electronic Devices Wuppertal GermanyShow Abstract
Atomic layer deposition (ALD) has been demonstrated to afford excellent gas permeation barriers, e.g. for the encapsulation of organic electronic devices . Conventional ALD is vacuum based and requires long processing times. Towards high-throughput and roll-to-roll manufacturing, spatial ALD has been introduced . Most of the work on spatial ALD relies on thermal processes (e.g. diethyl zinc and water). At low processing temperatures, thermal ALD in general is less favourable and plasma enhanced ALD (P-ALD) is a promising alternative . Work on spatial plasma enhanced ALD at atmospheric pressure (spatial APP-ALD) is very limited, as of yet. Until now, no gas permeation barriers prepared by spatial APP-ALD have been demonstrated.
In this work, we report on Al2O3 thin films deposited by spatial APP-ALD from TMA and Ar/O2 plasma with a growth per cycle of 0.18 nm. This in line with reports for reactor based low pressure P-ALD of Al2O3 . Processing speed and precursor saturation were investigated and compared to those found for spatial ALD based on water and ozone. Barrier properties were measured using an optical calcium test. We demonstrate that APP-ALD affords Al2O3 layers with water vapour transmission rates (WVTR) on the order of 10-4 gm-2d-1, comparable to that of films made by conventional thermal ALD.
 J. Meyer, P. Görrn, F. Bertram, S. Hamwi, T. Winkler, H.-H. Johannes, T. Weimann, P. Hinze, T. Riedl, and W. Kowalsky, Adv. Mater. 21, 1845-1849 (2009)
 P. Poodt, R. Knaapen, A. Illiberi, F. Roozeboom and A. van Asten, Journal of Vacuum Science & Technology A 30, 01A142 (2012)
 H. B. Profijt, S. E. Potts, M. C. M. van de Sanden, and W. M. M. Kessels, J. Vac. Sci. Technol. A 29(5) (Sep/Oct 2011)
 T.O. Kääriäinen, D.C. Cameron, Plasma Process. Polym, 6, S237-S241 (2009)
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Embossing Structure Using Spin-Coated Nanoparticles to Enhance the Performance of Organic Light-Emitting Diodes
Dohong Kim 1 Jun Hee Han 1 Kyung Cheol Choi 1
1KAIST Daejeon Korea (the Republic of)Show Abstract
Organic light-emitting diodes (OLEDs) are regarded as cutting-edge, next-generation displays due to the advantage of being easily adopted in transparent and flexible displays. However, the low out-coupling efficiency, approximately 20% in the case of typical OLEDs, should be enhanced for efficient display devices . Among the several ways of enhancing the out-coupling efficiency, inserting nanostructures to OLEDs is an effective method to extract trapped modes [2,3]. We fabricate a quasi-periodic nanoparticle layer by a one-step spin-coating approach without lithography or an imprint or lift-off process. The nanoparticle layer was adopted to emboss the OLED structure, resulting in improved performance of OLEDs. Inorganic SiO2 nanoparticles were quasi-periodically spread on the surface of indium tin oxide used as an anode in the OLED by spin-coating a SiO2 nanoparticle solution under appropriate parameters. A poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS, CLEVIOSTM P VP.Al 4083) layer was further coated as a hole injection layer (HIL). Due to the underlying nanoparticles, the PEDOT:PSS layer was naturally embossed. The height of the embossment was controlled by varying the size of the nanoparticles. Over the embossed PEDOT:PSS HIL, organic layers and a cathode were thermally deposited: 50 nm NPB (hole transporting layer) / 50 nm Alq3 (emitting layer) / 1 nm LiF (electron injection layer) / 100 nm Al (cathode). Compared with a flat OLED without the nanoparticles, the uneven OLED with the nanoparticles showed 0.2 V lower turn-on voltage at 1 cd/m2, 30% higher external quantum efficiency, and 60% higher power efficiency at 1000 cd/m2. The spin-coated PEDOT:PSS layer surrounding the nanoparticles injected holes to the NPB layer by detouring the inorganic nanoparticles. The embossment effectively shortens the distance between the PEDOT:PSS and Al layer, resulting in a higher electric field with lower driving voltage [4,5]. The nanostructured cathode layer helps to extract light from the waveguide and surface plasmon modes by Bragg diffraction.
Acknowledgement: This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIP)(CAFDC 5-1(0), NRF-2007-0056090) and was also supported by the Global Leading Technology Program funded by the Ministry of Trade, Industry and Energy, Republic of Korea (10042477).
 K. Saxena, V. K. Jain, D. S. Mehta, Opt. Mater. (Amst). 2009, 32, 221.
 J. Y. Kim, C. S. Choi, W. H. Kim, D. Y. Kim, D. H. Kim, K. C. Choi, Opt. Express 2013, 21, 5424.
 C. S. Choi, S.-M. Lee, M. S. Lim, K. C. Choi, D. Kim, D. Y. Jeon, Y. Yang, O. O. Park, Opt. Express 2012, 20 Suppl 2, A309.
 J. Y. Kim, W. H. Kim, D. H. Kim, K. C. Choi, Org. Electron. 2014, 15, 260.
 M. Fujita, T. Ueno, K. Ishihara, T. Asano, S. Noda, H. Ohata, T. Tsuji, H. Nakada, N. Shimoji, Appl. Phys. Lett. 2004, 85, 5769.
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Narrow Band Gap Conjugated Polymer For Improved Photovoltaic Performance of P3HT:PCBM Ternary Blend Bulk Heterojunction Solar Cells
Arun D. Rao 1 Murali M G 1 Scott A. Mauger 2 Logan Garner 2 Stefan Daniel Oosterhout 2 Nikos Kopidakis 2 Dana Olson 2 Praveen Chandrashekarapura Ramamurthy 1
1Indian Institute of Science Bangalore India2National Renewable Energy Laboratory Golden United StatesShow Abstract
#8203;A new D-A structured conjugated polymer (PBDO-T-TDP) based on electron-rich benzo[1,2-b:4,5-bprime;] difuron (BDO) containing conjugated alkylthiophene side chains with electron-deficient diketo- pyrrolopyrrole (DPP) derivative is designed and synthesized. The polymer shows a narrow band gap with broad UV-Visible absorption spectra, which complements with that of P3HT:PCBM binary blend. Further, its energy levels can meet the energetic requirement of the cascaded energy levels of P3HT and PCBM. Therefore, PBDO-T-TDP is used as a sensitizer in P3HT:PCBM based BHJ solar cells and its effect on the photovoltaic properties has been investigated by blending them together at various weight ratios. It is observed that the resulting ternary blend system exhibited a significant improvement in the device performance (~3.10 %) as compared with their binary ones (~2.15 %). Ternary blend devices showed improved current density of 12.6mA/cm2. But showed inferior in fill factor compared P3HT:PCBM. To understand its decrease in fill factor, CELIV was carried out. Which showed increase in bimolecular recombination for the ternary blend. Which indicate increase in disorder in the morphology of these films. TRMC was carried to understand photoconducantance properties of these films. Which indicate binary mixture (PBDOT-T-TDP with P3HT and PCBM) showed similar #8710;G to that of P3HT:PCBM binary mixture. Inorder to understand free charges generated PL measurments were carried out, which showed efficient quenching from these binary and ternary blends.
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A Novel Method to Fabricate Transparent Conductive Elastomeric Substrates with Embedded Electrodes Based on Silver Nanowires for the Application to Stretchable Electronic Devices
Jin-Hoon Kim 1 Jin-Woo Park 1
1Yonsei Univ Seoul Korea (the Republic of)Show Abstract
Demands for transparent stretchable electrodes have increased with the development of stretchable electronic devices such as a wearable strain sensor, triboelectric generator, and electronic skins. Among various stretchable substrate materials, poly(dimethylsiloxane) (PDMS) is most extensively used due to its superior mechanical stretchability, bio-compatibility, and optical transparency to other candidate materials. As the stretchable electrode, silver nanowire networks (AgNWs) are known to be the most promising candidate. With a high degree of stretchability, AgNWs generally have Rs as low as 25 Omega;/sq. at the transparency of 90 %. However, AgNWs have a high degree of surface roughness and non-uniform areal density with disconnected ends, which limits interface formation with the organic layers deposited atop the electrodes and results in electrical short in devices, respectively. Engineers have addressed these issues by embedding AgNWs into the PDMS. However, due to the low surface energy of PDMS, embedding of AgNWs into PDMS is challenging. In this study, we improved the transfer efficiency of AgNWs from the release substrate to the PDMS by inserting an interfacial layer of porous nano-particles between the AgNWs and PDMS. As the nano-particles have highly enhanced van der Waals interaction forces, the interfacial layer functions like a glue to transfer AgNWs from the release substrate to PDMS. AgNWs were spin-coated on a glass substrate, and the nano-particles were coated atop the networks. Then, the liquid PDMS was coated and thermally cured. After curing, PDMS and the release substrate were separated in the deionized water. This fabrication process is all-solution process; hence, can be applied to produce large area PDMS with the embedded electrodes. The surface roughness and area uniformity of the embedded electrodes were analyzed using atomic force microscopy and by Joule heating test, respectively. The strechability of the electrode was investigated by cyclic tension tests. According to our analysis results, there was little change in Rs of AgNWs before and after the transfer. The areal uniformity of AgNW distribution by the interfacial layer was also confirmed. Furthermore, the surface roughness of the embedded AgNWs is less than the AgNW-coating by more than an order. As the interfacial layer tightly hold the AgNWs, the AgNWs were highly deformed, but firmly welded with the PDMS under the stretching. As a result, the change in Rs after 1000 cycles of 25 % tensional strain was less than 10 Omega;/sq., which is a significant improvement compared to the previously reported results. On these embedded electrodes, stretchable organic light emitting diodes and triboelectric generators were successfully fabricated, which confirmed the great potential of the PDMS with embedded AgNWs as the substrates for various stretchable devices.
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Solution Sheared PEDOT:PSS as High Performance Transparent Conductors
Sean C Andrews 1 2 Brian Worfolk 1 Michael F. Toney 2 Stefan C.B. Mannsfeld 2 Zhenan Bao 1
1Stanford University Stanford United States2SLAC Menlo Park United StatesShow Abstract
Conductive films of high optical transparency are required in a myriad of optoelectronic applications, including lighting displays, touch sensors, and photovoltaics. Indium tin oxide (ITO) is the most widely used transparent conductive material due to the combination of low sheet resistance and high transparency when grown on a variety of substrates. However, alternative materials that do not require indium nor vacuum processing are desired. One possible ITO alternative is poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), which consists of insoluble PEDOT that is charge stabilized by PSS, affording good solubility in aqueous formulations. While there are many methods that can be used to deposit this and other polymer solutions, spin casting is the most popular laboratory scale technique due to its simplicity and ability to deposit high quality films with a variety of materials. However, spin casting is a batch process that is difficult to implement on a continuous mass production scale. Conversely, solution shearing enables scalable and controllable thin film fabrication. The tunable deposition conditions afforded by this technique enable kinetic control of morphology, composition, and ordering.
Herein, we utilize solution shearing to fabricate highly conductive thin films of PEDOT:PSS. Specific control over deposition conditions allows for tunable phase separation and preferential PEDOT backbone alignment, leading to superior performance to spin-casted films. Optical and x-ray measurements indicate PEDOT ordering with respect to the shearing direction. Optimized conditions enable electrical conductivities of 4600 ± 100 S/cm and reach sheet resistances of 17 ± 1 Omega;/#9633; at 97.2 ± 0.4 % transmission. Additionally, these high performance TC PEDOT:PSS films were utilized as patterned electrodes in capacitive touch sensors and organic photovoltaics to demonstrate their practical viability in optoelectronic applications.
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Ultra-Fast Laser Patterning Processes for Roll-to-Roll Manufacturing of Organic Photovoltaics onto Flexible Substrates
Stergios Logothetidis 1 Nikolaos Kontolatis 2 Christos Kapnopoulos 1 Evaggelos Mekeridis 2 Argiris Laskarakis 1 Vasileios Matskos 2
1Aristotle University of Thessaloniki Thessaloniki Greece2Organic Electronic Technologies P.C. (OET) Thessaloniki GreeceShow Abstract
Ultra-fast laser processes are attractive as alternative patterning techniques to photolithographic methods, and they have the advantage for implementation to roll-to-roll (r2r) manufacturing processes for the low-cost and large area production of flexible Organic Electronic devices, such as Organic Photovoltaics (OPVs) and Organic Thin Film Transistors (OTFTs). Laser processes offer much higher resolution than printing methods, whereas scribing by laser methods allows closer spacing of the P1, P2 P3 laser scribes, increasing the active area of the printed OPV device, which contribute to the increase of the OPV efficiency.
In this work, we present the innovative approach for the implementation of in-line laser scribing technique on a r2r printing pilot line for the ultra-fast laser scribing of inorganic and organic nanomaterials for flexible OPVs. These include state-of-the-art inorganic nanomaterials (e.g. Indium Tin Oxide-ITO, Zinc Oxide-ZnO), as well as transparent polymers (e.g. PEDOT:PSS) and photoactive blends consisting of mixtures of polymers as electron donors (e.g. polythiophenes) with fullerene-based electron acceptors (e.g. PCBM) in single and multilayer structures. The above innovative methodology opens the way for the wide implementation of ultra-fast laser processes for the r2r manufacturing of Organic and Printed Electronics devices.
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Contact Angle Optimization for Oxygen/Nitrogen Plasma Treated PEDOT:PSS/Si Hybrid Systems
Kenneth D Shaughnessy 1 Emma G Langford 1 Chester Joseph Szwejkowski 2 Patrick Edward Hopkins 2 Costel Constantin 1
1James Madison Univ Harrisonburg United States2University of Virginia Charlottesville United StatesShow Abstract
This work presents a study on the effects of plasma treatment on the wettability of silicon and fused silica for the deposition of Poly (3,4 ethyldioxythiophene) Polystyrene Sulfonate (PEDOT:PSS) via drop-casting or spin-coating. Silicon and fused silica substrates were sonicated in acetone, isopropyl alcohol, and methanol for 5 minutes each, then plasma treated for various amounts of time (i.e., 30, 60, 300, and 600 seconds) in either 100 parts oxygen plasma or 3 parts nitrogen and 100 parts oxygen plasma. To determine which conditions yielded the optimal surface energy, and thus wettability, the contact angles of PEDOT:PSS were measured via two methods, namely, 1) goniometry by using a Rame-Hart 290 instrument and 2) profilometry by using a KLA Tencor P-7 stylus profiler. Preliminary results show that both methods yield similar results for the lowest contact angle. The presented results are of interest for academic and industrial processing of hybrid photovoltaic devices.
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Optimizing the Morphology of Organic Bulk Heterojunction Films Using Solvent Additives in the Photoprecursor Approach
Yuji Yamaguchi 1 2 Mitsuharu Suzuki 3 Tomoyuki Koganezawa 5 Hiroko Yamada 3 4 Ken-ichi Nakayama 1 2 4
1Yamagata Univ Yonezawa Japan2ROEL Yonezawa Japan3Nara Institute of Science and Technology Ikoma Japan4CREST Kawaguchi Japan5Japan Synchrotron Radiation Research Institute Sayo-gun JapanShow Abstract
We have recently reported that the photoprecursor approach can serve as an effective means to prepare multi-layer thin films through solution processes.1 There, we employed 2,6-dithienylanthracene diketone (DTADK) as a photo-reactive precursor of p-type material 2,6-dithienylanthracene (DTA). Since DTA is essentially insoluble to most organic solvents, one can solution-deposit a different material on top of a DTA film, or even a composite film of DTA and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM). We constructed p-i-n active layers by taking advantage of this characteristics, which showed much higher power conversion efficiency than that of the corresponding bulk heterojunction (BHJ) device (1.50% for the p-i-n, and 0.88% for the BHJ device, respectively). 1 While this preliminary work showed the advantage of p-i-n structure, it also indicated that there was much room for improvement in the BHJ system prepared by the photoprecursor approach. This study presents the effect of solvent additive on the morphology and electric properties of DTA:PC71BM BHJ films.
In this work, we compare BHJ films deposited by using chloroform as a solo solvent and those deposited using o-dichlorobenzene (ODCB) as an additive in chloroform. The structure of these device can generally be described as [ITO/PEDOT:PSS/DTA:PC71BM/Ca/Al]. Without the ODCB additive, the resulting device showed a PCE of 0.44% associated with a low short-circuit current density (Jsc) of 1.75 mA cm-2 and fill factor (FF) of 24.4%, and a significantly high series resistance (Rs) of 471 W cm2. When chloroform containing 15% ODCB was used as deposition solvent, the PCE was greatly improved to 2.11% associated with a FF of 50.4% and Rs of 44 W cm2, and Jsc of 4.45 mA cm-2. Two-dimensional grazing-incidence X-ray diffraction (2D-GIXD) analyses showed that the latter BHJ film has randomly oriented microcrystalline domains of DTA, while the former is essentially amorphous. It was assumed that the higher boiling-point solvent remained during the photoreaction from DTADK to DTA, allowing DTA molecules to reorganize to form microcrystals, which might be advantageous in forming effective charge-carrier paths in the film. It would be worth noting that adding too much ODCB (>20%) resulting in the enhancement of the end-on mode packing of DTA, which is unfavorable for vertical carrier transport, thereby leading to lower PCEs.
These results clearly demonstrate the positive impact of solvent additive in improving the performance of the BHJ system prepared by the photoprecursor approach. Further investigation into processing conditions is underway employing different photoconvertible materials. This presentation will also include the updates along these lines.
(1) Yamaguchi, Y et al., Sci. Rep., 2014, 4, 7151.
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Conducting Polymer Nanosheets Fabrication with a Roll-to-Roll Process and Their Application as Skin-Contact Electrodes
Alessandra Zucca 1 2 Kento Yamagishi 3 Toshinori Fujie 3 4 Shinji Takeoka 3 4 Virgilio Mattoli 1 Francesco Greco 1
1Istituto Italiano di Tecnologia Pontedera Italy2Scuola Superiore Sant'Anna Pontedera Italy3Waseda University Shinjuku, Tokyo Japan4Waseda University Shinjuku, Tokyo JapanShow Abstract
Ultra-thin polymeric films combined with conductive materials and/or embedding electronic devices are envisioned as ideal candidate materials for the development of unperceivable personal monitoring systems to be used in healthcare and sport, in particular as regards skin-contact applications. Indeed, their ultra-low thickness (few micrometers or less) allows for the intimate contact between such films and target surfaces onto which they conformally adhere, including skin. The challenge, in this view, is to reduce the overall thickness and at the same time to provide for reliable and robust strategies for production, handling, release and positioning of these extremely thin films, while maintaining the structural integrity and function of electrodes (used, as example, for physiological signals recording) and other on-board electronic components. On the other hand, the adoption of industry-ready, high throughput, large area fabrication processes is demanded for achieving cost-effectiveness and speed of execution, towards mass-scale manufacturing.
Based on our previous studies dedicated to fabrication and patterning of free-standing conducting polymer nanosheets prepared by spin coating on small scale substrates,[3-4] here we report a roll-to-roll (R2R) process which permits the upscaling of this technology to large area and continuous manufacturing. R2R conductive nanosheets are obtained as bilayer structures with overall thickness 60 < t < 350 nm, comprising a functional layer of poly(3,4-ethylenedioxythiophene) : poly(styrene sulfonate) (PEDOT:PSS) and a support layer of poly(D,L lactic acid) (PDLLA). Their release as free-standing films from a temporary substrate (plastic film roll) permits their transfer in conformal contact to any target surface with arbitrary shape, curvature and surface topography (including biological tissues and skin) to whom nanosheets strongly adhere without the use of any adhesive, as evaluated in adhesiveness tests. Specific high-conductivity formulations of PEDOT:PSS have been optimized making use of dimethylsulfoxide or butylene glycol (BG) as dopants. The latter, a dermatologically approved ingredient, is specifically intended for skin-contact applications. As a first demonstration of application in bioelectrical sensing, the R2R nanosheets are tested as unperceivable surface electromyography electrodes able to record muscle electric activity. Nanosheets have comparable performance with respect to standard pregelled electrodes used in clinical practice, in terms of signal to noise ratio. Moreover, nanosheets worn on the skin shows very good mechanical and electrical stability against body movement and sweating, also after prolonged use (several hours).
1. M. Kaltenbrunner et al., Nature499, 458 (2013).
2. D. H. Kim et al., Science333, 838 (2011).
3. F. Greco et al., Soft Matter 7, 10642 (2011).
4. F. Greco et al., ACS Appl. Mater. Interf. 5, 9461 (2013).
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Electrical and Microstructure Characterization of Ion-Gel Gated Electrochromic Transistors
Francis Quenneville 1 Xiang Meng 1 Eduardo Di Mauro 1 Francesca Soavi 2 Clara Santato 1
1Ecole Polytechnique Montreal Montreal Canada2Universitagrave; di Bologna Via Selmi ItalyShow Abstract
We report on thin tungsten trioxide (WO3) films in electrolyte-gated transistor configuration using, as the electrolyte, ion-gels, such asPS-PMMA-PS/[EMIM] [TFSI] and PS-PEO-PS/[EMIM] [TFSI]. These ion gels are known to self-assemble into different microstructures depending on the copolymer/ionic liquid ratio . We therefore studied these microstructures for applications in electrolyte-gated WO3 electrochromic transistors . Thin films of sol-gel tungsten trioxide were drop cast on pre-patterned chemically-etched ITO on glass and thermally treated at ca 450 °C; ion-gels were spin-coated on the WO3 films .
We performed spectroelectrochemistry measurements on our transistors, coupling a hyperspectral imaging system (Pariss) to a semiconductor parameter analyser. We extracted the transmission spectra of the WO3 films from different locations within the transistor channel, both in the ON (electrical bias applied, Vgs ca 2 V and Vds ca 1 V) and in the OFF state. We established an extended correlation between the nature of the electrolyte selected (in particular of its viscosity and ionic conductivity) and the microstructure of the ion-gel (characterized by AFM) to quantitatively describe the advancement of the doping front in the electrochromic transistors.
Efforts are underway to render the sol gel synthesis of the films compatible with the deposition on flexible substrates. This would permit to demonstrate flexible electrochromic transistors to reach new applications in the automotive industry, smart labelling and inventory tracking.
 P. M. Simone and T. P. Lodge, “Phase behavior and ionic conductivity of concentrated solutions of polystyrene-poly(ethylene oxide) diblock copolymers in an ionic liquid.,” ACS Appl. Mater. Interfaces, vol. 1, no. 12, pp. 2812-20, Dec. 2009.
 C. G. Granqvist, Handbook of Inorganic Electrochromic Materials. Elsevier, 1995, pp. 499-518.
 K. H. Lee, S. Zhang, T. P. Lodge, and C. D. Frisbie, “Electrical impedance of spin-coatable ion gel films.,” J. Phys. Chem. B, vol. 115, no. 13, pp. 3315-21, Apr. 2011.
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Revealing the Morphology of Ternary Bulk Heterojunction Organic Solar Cells Using Analytical Transmission Electron Microscopy
Stefanie Fladischer 1 2 Nicola Gasparini 1 Christos L. Chochos 3 Erdmann Spiecker 2 Christoph Brabec 1 Tayebeh Ameri 1
1Friedrich-Alexander University Erlangen-Nuuml;rnberg Erlangen Germany2Friedrich-Alexander University Erlangen-Nuuml;rnberg Erlangen Germany3University of Ioannina Ioannina GreeceShow Abstract
Ternary bulk heterojunction (BHJ) organic solar cells are a novel concept to overcome the limited absorption spectrum of organic semiconductors. In this concept the spectral sensitivity is enhanced by adding infrared sensitizers to the host system consisting of a wide bandgap polymer blended with fullerene derivatives to enhance light harvesting properties as well as the power performance of the single BHJ organic solar cell.1 Such sensitizers have a strong impact on the morphology of the active layer, which in turn decisively influences the performance of the ternary organic solar cell. In this work the nanocomposite structure of a ternary organic solar cell is investigated by combining advanced techniques of analytical transmission electron microscopy (TEM). To the best of our knowledge this is the first time that the material distribution of an active layer in a ternary solar cell is visualized for all three organic materials using analytical TEM.
The ternary organic solar cell under investigation comprises the high band gap polymer indacenodithieno[3,2-b]thiophene,2,3-bis(3-(octyloxy)phenyl)quinoxaline (PIDTTQ), the near infrared (NIR) active sensitizer poly[(4,4&’-bis(2-ethylhexyl)dithieno[3,2-b:2&’,3&’-d]silole)-2,6-diyl-alt-(4,7-bis(2-thienyl)-2,1,3-benzothiadiazole)-5,5&’-diyl] (Si-PCPDTBT) and the fullerene [6,6]-phenyl C70 butyric acid methyl ester (PC70BM). The cell features a pronounced sensitization effect resulting in a power conversion efficiency of more than 6% at 0.01 suns (1 mW cm-2).
Electron energy-loss spectroscopy (EELS) and energy filtered TEM (EFTEM) were combined with energy-dispersive X-ray spectroscopy (EDXS) to successfully identify and distinguish the three materials in the blend. In the case of the mixing ratio PIDTTQ:Si-PCPDTBT:PC70BM 0.5:0.5:2 the fullerene forms domains with diameters in the range of about 200 nm and the host polymer PIDTTQ surrounds these domains. In comparison to the binary blend, where the fullerene domains are in the range of 50 nm, the PC70BM domain size is increased tremendously in the ternary blend. The sensitizer Si-PCPDTBT forms needle or plate like structures that are equally distributed in the whole blend. These Si-PCPDTBT structures are found in the polymer as well as in the fullerene domains as well as at the interfaces. Further mixing ratios will be investigated to elucidate the phase formation of this ternary blend system.
Financial support by the Marie Curie Initial Training Network (ITN) within the European Union&’s Seventh Framework Programme (Grant agreement no. 607585, OSNIRO), the German Science Foundation (DFG) via the Cluster of Excellence EXC 315 “Engineering of Advanced Materials”, the SFB953 “Synthetic C-Allotropes” and “Solar Technologies go Hybrid” (SolTech) is gratefully acknowledged.
1) T. Ameri, P. Khoram, J. Min, C.J. Brabec, Adv. Mater. 25 (2013) 4245-4266
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Photo-Patterned Two-Color Micro-OLED Array for Lighting Applications
Simonas Krotkus 1 Daniel Kasemann 1 Simone Hofmann 1 Malte C Gather 1 Karl Leo 1 Sebastian Reineke 1
1Technische Universitauml;t Dresden Dresden GermanyShow Abstract
White organic light emitting diodes (WOLEDs) attract huge research and commercial interest due to their high efficiency, inherent flexibility, lightweight and large-area emission, showing great potential to contribute strongly to general illumination in the future . Besides, the possibility to reliably tune the emission color of WOLEDs - both for lighting and display applications - is also desired. While most of the research is focused on devices containing multiple emission layers, such WOLEDs suffer from the undesired voltage-dependent spectrum resulting from a variety of complex physical mechanisms which make controlled color change while keeping the brightness level constant hardly possible.
On the other hand, lateral alignment of monochrome OLED devices and addressing them via separate current drivers enables combination of efficient and stable illumination together with the possibility of controlled tuning of the emission color. However, such approach requires complicated and expensive processing when fine metal masks are used for structuring of the OLEDs, which ultimately leads to limitations in resolution and substrate size and is hence seldom used to fabricate WOLED devices.
Whereas photo-lithographic patterning is a well-established, up-scalable, high yield/resolution technique persistently used in inorganic semiconductor industry, its use in structuring organic electronic devices to date is rather limited, due to the processing of organic and/or water-based solvents, etchants and photoresists. The latter are known to be detrimental to most of the organic semiconductors. Recently, our group presented highly efficient vacuum deposited single color OLED photo-patterned down to the tens of micrometers using orthogonal processing approach . Our method is based on a bilayer concept, enabling lift-off in hydrofluorother solvents, which are shown to be compatible with state-of-the-art OLED technology.
In this work, we present laterally aligned micro-OLED array consisting of efficient fluorescent blue and phosphorescent yellow devices comprising organic layer sequence optimized for orthogonal processing. Photo-structuring of the OLEDs down to 20µm was achieved by lift-off in HFEs. The resulting sub-units sit side-by-side without gap in between and can be addressed separately leading to reliable control of the emission color from blue to cold white to warm white to yellow under constant luminance. Furthermore, photo-lithographic size control of each of the subunits and its effect on device lifetime is discussed. Finally, ways to extend the photo-lithographic approach to structure three or more monochrome devices are presented.
 S. Reineke, “Complementary LED Technologies”, Nature Mater. 14, 459 (2015)
 S. Krotkus, F. Ventsch , D. Kasemann, A. A. Zakhidov, S. Hofmann , K. Leo, M. C. Gather, “Photo-patterning of Highly Efficient State-of-the-Art Phosphorescent OLEDs Using Orthogonal Hydrofluoroethers”, Adv. Optical Mater. 2, 1043 (2014)
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Synthesis of Transparent Semiconducting Metal-Oxides via Polymeric Precursor Route for Application in Thin-Film Field-Effect Transistors
Cleber Amorin 2 Giovani Gozzi 2 Dante Luis Chinaglia 2 Lucas Fugikawa Santos 1 2
1UNESP Sao Jose do Rio Preto Brazil2UNESP Rio Claro BrazilShow Abstract
Transparent semiconducting metal-oxides like zinc oxide (ZnO), indium zinc oxide (IZO) and indium gallium oxide (IGZO) have been widely used as active layer of thin-film transistors (TFTs) envisaging applications in large-area active matrix displays and in totally transparent circuitry due to their considerably high charge-carrier mobility, optical transparency in the visible range of the electromagnetic spectrum and stability. Recently, TFTs comprising solution-processed metal oxides obtained via hydrolysis/pyrolysis of an organic precursor have achieved electrical performance which challenges metal-oxide TFTs produced by traditional deposition methods (e.g. RF sputtering), presenting attractive characteristics as low manufacturing cost and possibility to cover large-areas. However, solution-processed metal oxide thin films still suffer from undesirable characteristics such as film non-uniformity, high porosity and unstable electrical response. In order to circumvent these problems, we have used an alternative method, based on a polymeric precursor route (Pecchini) to obtain more compact and uniform metal oxide films via solution processing. The elimination of the organic phase and the formation of inorganic thin-films was carried out by thermal treatment at different temperatures (ranging from 200oC to 500 oC) and at different times (from 5 min to 2 hours) and was monitored by optical absorption in the UV-vis and the IR ranges (FTIR). It was observed that, for temperatures above 350oC and times superior to 30 min, the organic phase was completely eliminated and the metal oxide phase was achieved. The optical bandgap of the resulting ZnO films, determined from UV-vis absorption, is about 3.4 eV. Film crystallinity and stoichiometric composition of the thin-films were determined by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX), respectively. Film morphology and thickness were studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The electrical properties were performed by d.c. current-voltage measurements (output and transfer curves) in a bottom-gate, bottom-contact thin-film field effect transistor structure using p-type Si substrates with a thermal grown SiO2 dielectric layer (90 nm to 300 nm), by capacitance-voltage measurements and by impedance spectroscopy. The electrical properties (charge-carrier mobility, threshold voltage, semiconductor capacitance dependence on voltage and excitation frequency and current stability) of the fabricated electronic devices show a significant improvement o