Aline Rougier, Institut de Chimie de la Matière Condensée de Bordeaux
Smagul Karazhanov, Institute for Energy Technology (IFE)
John Reynolds, Georgia Institute of Technology
Kazuki Yoshimura, Advanced Industrial Science and Technology (AIST)
ES07.01: Electrochromic I
Monday PM, November 27, 2017
Hynes, Level 3, Room 301
8:30 AM - *ES07.01.01
Transparent Intelligence—Electrochromic Glazing Today and Tomorrow
Claes-Goran Granqvist 1 Show Abstract
1 , Uppsala Univ, Uppsala Sweden
Electrochromic (EC) glazing is currently introduced in buildings, particluarly in Europe and the US, and provides energy efficiency jointly with indoor comfort and other amenities. This paper introduces the basics of this technology and then dicusses how web coating and lamination can be implemented in order to facilitate production and logistics of EC glazing. The second part of the presentation ventures to look at future possibilities, in particular (1) how electrolyte functionalization can yield superior properties and (2) how elecrochemical treatments of EC thin films can lead to increased durability and enable rejuvenation.
9:00 AM - ES07.01.02
Dynamic Windows with Fast Switching, Neutral Color, Excellent Durability and Low Cost Using Reversible Metal Electrodeposition
Michael McGehee 1 , Daniel Slotcavage 1 , Christopher Barile 2 1 , Tyler Hernandez 1 , Michael Strand 1 Show Abstract
1 , Stanford University, Stanford, California, United States, 2 Chemistry, University of Nevada, Reno, Reno, Nevada, United States
While a handful of dynamic glass technologies exist in the automotive, architectural, and aviation industries, none of them perform ideally. Tackling the largest challenges facing electrochromics, we have created a low-cost, fast-switching, color-neutral, durable technology to achieve both significant energy savings and a beautiful aesthetic. We based these devices on reversible metal electrodeposition. Because of their electronic structure, metals have large complex refractive indices and interact strongly with light. Consequentially, very small amounts of metal deposited quickly yield significant optical modulation. By adjusting the metals and supporting anions in our gel electrolyte, we have tuned the optical response of our deposits to achieve neutral black transmission. The transmission versus average metal thickness is not described by Beer’s Law because the films consist of very closely spaced metal nanoparticles. Our electrodeposited films reflect minimally because of the wide size and shape distribution of electrodeposited features. Ranging from nanometers to microns, the smallest metal nanostructures promote broad plasmonic absorption while the largest promote internal reflections. By utilizing a chemically inert seed layer, we have demonstrated 25 cm2 sealed devices with uniform deposition that switch reversibly over thousands of cycles. Finally, we designed these devices with large-scale production in mind. Using a simple device stack constructed via industrially scalable techniques suppresses costs from both production and materials. Our plans for producing electrodes with low sheet resistance and scaling the technology to meter-wide windows will be presented.
9:15 AM - ES07.01.03
Switchable Photovoltaic Windows Enabled by Reversible Photothermal Complex Dissociation from Metal Halide Perovskites
Lance Wheeler 1 , Rachelle Ihly 1 , David Moore 1 , Noah Stanton 1 , Jeffrey Blackburn 1 , Nathan Neale 1 Show Abstract
1 , National Renewable Energy Laboratory, Lakewood, Colorado, United States
We demonstrate the first photovoltaic device with a “switchable” absorber layer that dynamically and automatically responds to sunlight. Upon illumination, photothermal heating switches the absorber layer – composed of an organic metal halide perovskite complex – from a transparent state (68% visible transmittance) to a highly absorbing colored state (<3% visible transmittance) due to dissociation of the complex. In the dissociated colored state, the photovoltaic device exhibits a solar power-conversion efficiency of 11.3%. After cooling, the complex is reformed, returning the absorber layer to the transparent state in which the device acts as a window. This dynamic equilibrium between complexed and dissociated states is driven by the thermodynamics described by the Clausius-Clapeyron relation, and the pressure-temperature dependance of phase transitions was investigated using in situ differential FTIR spectroscopy. This work validates a new concept in PV window technology that circumvents the fundamental trade-off between efficient solar conversion and high visible light transmittance that limits conventional semitransparent PV window designs.
9:30 AM - ES07.01.04
Electrode and Electrolyte Effects in Reversible Metal Electrodeposition for Dynamic Windows
Christopher Barile 1 2 , Daniel Slotcavage 1 , Michael Strand 1 , Tyler Hernandez 1 , Michael McGehee 1 Show Abstract
1 Materials Science and Engineering, Stanford University, Stanford, California, United States, 2 Chemistry, University of Nevada, Reno, Nevada, United States
Dynamic windows, which switch between transparent and opaque states upon application of a voltage, have applications in buildings, automobiles, and switchable sunglasses. We describe dynamic windows based on the reversible electrodeposition of Cu and a second metal (Pb or Ag) on transparent indium tin oxide (ITO) electrodes modified by Pt nanoparticles. Aqueous Cu-Pb and Ag-Cu electrolytes are developed with Cl- as a deposition accelerant. The Pt nanoparticles enable uniform electrodeposition by facilitating nucleation across the area of the ITO electrode. Metal electrodeposition occurs preferentially on the inert Pt seed layer, providing a stable platform for reversible metal electrodeposition over thousands of cycles. Three-electrode cyclic voltammetry experiments demonstrate the electrolytes possess high Coulombic efficiency (99.9%), indicating that the metal electrodeposition and stripping processes are reversible. Two-electrode 25 cm2 windows without bus bars uniformly switch between a transparent state (~80% transmission) and a color neutral opaque state (<5% transmission) in less than three minutes. Taken together, these results indicate that dynamic windows based on reversible metal electrodeposition are a promising alternative to those using traditional electrochromic materials.
9:45 AM - ES07.01.05
Self-Powering, Electrically Switchable Chromogenic Windows
Joseph Murray 1 , Dakang Ma 1 , Jeremy Munday 1 Show Abstract
1 , University of Maryland, College Park, Maryland, United States
Switchable windows allow the user to control the amount of transmitted light and offer significant advantages over traditional windows by reducing glare, room heating, and electricity costs. However, most mechanisms for reducing transmission introduce optical loss, which results in waste heat generation. Here we present a hybrid switchable window device based on polymer dispersed liquid crystals coupled to a semiconducting absorber that enables transparency control and the opportunity to simultaneously generate power through operation as a solar cell . By applying a voltage across the layer, the device switches from an opaque (useful for room light dimming, privacy, and temperature control) to clear (useful for room illumination). Fabricated devices require no power in the opaque, scattering state and less than 0.8 mW/cm2 in the transparent state. By incorporating as little as 13 nm of a-Si, 1 mW/cm2 of power can be generated, enabling self-powering.
 Joseph Murray, Dakang Ma, and Jeremy N. Munday, ACS Photonics, 4, 1–7, (2017)
10:30 AM - *ES07.01.06
The Development of Fast and Uniform Switching Electrochromic Devices and Smart Tinting Glass
Howard Turner 1 Show Abstract
1 , Kinestral Technologies, Hayward, California, United States
Kinestral Technologies was founded in 2010 to develop materials and coating processes for producing durable, oxide-based electrochromic devices with improved optics and switching performance. Key technological advances that enable "Halio Smart Tinting Glass" to switch rapidly (~ 3 minutes), uniformly (no Iris effect), between high quality optical states will be described.
11:00 AM - ES07.01.07
Copper-Based Reversible Electrochemical Mirror Device with Switchability between Transparent, Blue and Mirror States
Alice Eh 1 , Meng-Fang Lin 1 , MengQi Cui 1 , Guofa Cai 1 , Pooi See Lee 1 Show Abstract
1 , Nanyang Technological University, Singapore Singapore
Conventional reversible electrochemical mirror (REM) devices are limited to switchability between transparent and mirror states. It is also challenging to maintain the mirror state of the REM devices due to the diffusion of anions into the metallic film at the open-circuit state. To overcome these limitations, we report a Cu-based REM device, which offers reversible switching between transparent, blue and mirror states with judicious selection of electrolyte and controllable electrodeposition. This tri-state REM device is one of the first to demonstrate electrochemical tunability to deliver clear, colored and reflective modulations in a single electrochromic device. The blue colored state can be obtained through the formation of copper (I) chloride, CuCl, when copper (II) chloride CuCl2 undergoes electrochemical reduction. The mirror state is formed when CuCl undergoes electrochemical reduction to Cu0 metal. The clear state can be obtained when the electrodeposited Cu0 metal oxidizes upon application of reverse potential and dissolves back into the electrochromic solution, thereby increasing the optical transmittance of the working electrode. The polymer host, PVA (poly(vinyl alcohol)) plays a crucial role in reducing the surface roughness of the electrodeposited mirror film, improving film uniformity and sustaining the mirror state of the device during the voltage-off state. Additionally, the REM device is operational using low voltage with standard battery and allows memory effect for energy conservation application for green buildings and electronic devices.
11:15 AM - ES07.01.08
Plasmonic Nanoparticle-Containing Dual Responsive Composite for Climate-Adaptable Autonomous Solar Modulating Window
Heng Lee 2 , Yufeng Cai 2 , Shuguang Bi 2 , Yen Nan Liang 2 , Yujie Song 2 , Xiao 'Matthew' Hu 2 1 Show Abstract
2 School of Materials Science and Engineering, Nanyang Technological University, Singapore Singapore, 1 Environmental Chemistry and Materials Centre, Nanyang Environment & Water Research Institute, Singapore Singapore
In this work, a novel fully autonomous photothermotropic material made by hybridization of the poly(N-isopropylacrylamide) (PNIPAM) hydrogel and antimony−tin oxide (ATO) is presented. In this photothermotropic system, the near-infrared (NIR) active ATO acts as plasmonic nanoheater to induce the optical switching of the hydrogel. Such a new passive smart window is characterized by excellent NIR shielding, a photothermally activated switching mechanism, enhanced response speed, and solar modulation ability. Systems with 0, 5, 10, and 15 atom % Sb-doped ATO in PNIPAM were investigated, and it was found that a PNIPAM/ATO nanocomposite is able to be photothermally activated. The 10 atom % Sb-doped PNIPAM/ATO exhibits the best response speed and solar modulation ability. Different film thicknesses and ATO contents will affect the response rate and solar modulation ability. Structural stability tests at 15 cycles under continuous exposure to solar irradiation at 1 sun intensity demonstrated the performance stability of such a photothermotropic system. We conclude that such a novel photothermotropic hybrid can be used as a new generation of autonomous passive smart windows for climate-adaptable solar modulation.
11:30 AM - *ES07.01.09
Multifunctional Electrochromic Nanomaterials and Devices
Pooi See Lee 1 Show Abstract
1 School of Materials Science and Engineering, Nanyang Technological University, Singapore Singapore
Electrochromic fenestration enables an active and dynamic control of light or heat transmission into a building, and promotes the viability for energy savings. The optical modulation or optical contrast of the electrochromic smart glass can be tuned by the particle size, morphology, phase and structural properties of the active layer, while the switching kinetics of the smart glass can be altered by the ease of ions diffusion and intercalation. With our earlier established work on various electrochromic nanomaterials such as WO3, NiO, ethyl viologens on transparent conductors such as ITO, FTO, silver grid/PEDOT substrates, silver nanowires on cellulose substrates, the progresses of multifunctional smart window will be discussed.1-4 Inkjet printing technique is one of the low cost and solution processible methods that is promising for uniform coating and fine patterning. Our efforts on inkjet printable multifunctional smart windows have been demonstrated on device size of 300 cm2. The assembled electrochromic windows exhibit outstanding performance including large optical modulation, high coloration efficiency, fast switching and excellent bistability. The designed multifunctional smart window has been shown to function as a typical electrochromic window as well as energy-storage device. This allows us to monitor the level of stored energy in the window via the visually detectable reversible color variation, presenting a fascinating energy-efficient smart glass. Finally, the possibility of achieving tri-state electrochromics with reflective, colored and transparent states will be discussed.
Cai, G.; Wang, J.; Lee, P. S. Acc. Chem. Res. 2016, 49, 1469.
Cai, G.; Darmawan, P.; Cui, M.; Wang, J.; Chen, J.; Magdassi, S.; Lee, P. S. Advanced Energy Materials 2016, 6, 1501882.
Eh, A. L.-S., Lin, M. F.; Cui, M., Cai, G.; Lee, P. S. J. Mat. Chem. C. 2017, 5, 6547.
ES07.02: Electrochromic II
Monday PM, November 27, 2017
Hynes, Level 3, Room 301
1:30 PM - *ES07.02.01
Synthesis of Metal Oxide Nanoparticles for Electrochromic and Thermochromic Applications
Elvira Fortunato 1 , Rodrigo Martins 1 Show Abstract
1 , FCT-UNL, Caparica Portugal
Metal oxide nanoparticles have attracting a huge interest in the last decade due to the wide range of possible applications especially due to the possibility to add new functionalities to devices and systems.
Nanoparticles, not only present a reduced size as well as high reactivity, which allows the development of electronic, optical and electrochemical devices with exclusive properties, when compared for example with thin films.
Here we present the optimization of tungsten trioxide nanoparticles produced via hydrothermal synthesis for application in electrochromic devices and detection of electrochemically active bacteria as well as the optimization of smart optically active VO2 nanostructured layers applied in roof-type ceramic tiles for energy efficiency.
2:00 PM - ES07.02.02
Influence of Structural Distortions on Optical Absorption in WO3
Wennie Wang 1 , Hartwin Peelaers 1 , Jimmy-Xuan Shen 2 , Chris Van de Walle 1 Show Abstract
1 Materials, University of California, Santa Barbara, Santa Barbara, California, United States, 2 Department of Physics, University of California, Santa Barbara, Santa Barbara, California, United States
Tungsten oxide (WO3) is a widely studied electrochromic material used in a variety of display and energy-saving applications. While there have been many studies on the optical and electrical properties of WO3, a microscopic picture of how optical absorption varies with injection of excess charge carriers is lacking. Going beyond the phenomenological Drude model, we present a first-principles study to understand the microscopic mechanisms of the optical absorption due to excess carriers in WO3.
Using state-of-the-art hybrid density functional theory calculations, we investigate the influence of structural distortions on the absorption spectra by comparing the cubic, monoclinic, and amorphous phases. We present a tractable methodology to calculate absorption from first principles. Our results show that interband absorption occurs predominantly at infrared and near-infrared wavelengths, regardless of structural distortions. We discuss how the changes in electronic structure and bonding contribute to this behavior, which also provides valuable insight for understanding other chromogenic materials.
2:15 PM - ES07.02.03
From Modified Opto-Electronic Properties of Tungsten Oxide Nanoparticles towards Electrochromic Films
Marie Bourdin 1 2 , Thierry Cardinal 1 , Manuel Gaudon 1 , Younès Messaddeq 2 , Aline Rougier 1 , Issam Mjejri 1 Show Abstract
1 , Institut de Chimie de la Matière Condensée de Bordeaux, Pessac France, 2 , Centre d'Optique, Photonique et Laser, Quebec, Quebec, Canada
WO3 compounds are school-case example of “X-chromic” or “chromogenic” oxides with tuneable optical properties because of external means such as UV irradiation (photochromism) or application of an electrochemical potential (electrochromism). WO3 is a well-known active electrode compound for electrochromic devices based on the redox of the W element linked to the ability of the ReO3-like structure to accept proton and/or alkaline insertion-desintertion .
In our work, specific attention was given to the materials synthesis, herein a modified-polyol precipitation route . (Hx)WO3-δ nanoparticles are directly obtained thanks to the reductive effect of the di-ethylene-glycol used as precipitation medium. Another advantage of this synthesis route is large possibilities of doping with various elements as Sr2+, Ca2+, Ti4+, etc. The as-obtained particles are deep blue coloured due to large sub-stoichiometry ; a post-annealing treatment at moderate temperatures (in the range 100°C-600°C) within various atmospheres (10-5 bar ≤ PO2≤ 10-1 bar), allow a control of the W/O ratio and so the compound coloration (from black to bright yellow).
The effect of the annealing treatments on particle morphology (size distribution and shape), crystallographic structure, W/O balance and their correlation is investigated coupling X-Ray Diffraction, TEM, EPR, HNMR, TGA and XPS. It was shown that changing the oxygen partial pressure from 10-3 to 10-4 bar with an annealing temperature fixed at 600°C, both (i) the particle size and shape (from isotropic to rod-like crystals), (ii) the structure (from cubic to monoclinic), (iii) W5+/W6+ ratio and so the optical (UV-Vis-NIR diffuse reflectance spectra) and electrical properties, drastically changed. Comparing these two samples, (i) electrical conductivity shows that both samples exhibit a semi-conducting behaviour but with very different energy gaps (correlated here to the polaron hopping barrier), (ii) optical properties of the 10-4 bar annealed sample is nearly fully absorbent on UV-vis-NIR range whereas the 10-3 bar annealed one presents a narrow window of transparency in the visible range (what is very interesting for solar filter applications).
Last part of the work is devoted to electrochromic film tests, the films being elaborated using dip-coating process (ethanol-based inks allowing suitable dispersion are used). In situ voltametric cycles and in situ diffuse transmission through the as-prepared films were measured vs applied voltages. The electrochromic performances (from blue to yellow in oxidative/reducing condition, respectively) in terms of optical contrast are promising.
 S.K. Deb, 1973. Philos. Mag. 27, 801
Granqvist, C.G., 2005. J. Eur. Ceram. Soc., Elecroceramics IX 25, 2907–2912
 Porkodi, P., et al., 2006. Mater. Res. Bull. 41, 1476–1486
Avellaneda, C.O., et al., 2003. Solid State Ion., Fifth International Meeting on Electrochromism 165, 117–121
2:30 PM - ES07.02.04
WO3 Nanoparticle Engineering for Printed Electrochemical Applications
Elvira Fortunato 1 , Rodrigo Martins 1 Show Abstract
1 , FCT-UNL, Caparica Portugal
Then aim of this talk is to discuss the engineering procedures governing the selection or development of printable nanostructured metal oxide nanoparticles for chromic, photovoltaic, photocatalytic, sensing, electrolyte-gated TFTs, and power storage applications. The main focus is given on how to perform the material selection and formulation of printable dispersion in order to develop functional films for electrochemical applications.
Firstly, a brief introduction on electrochemically active nanocrystalline metal oxide films developed via printing techniques is given. This is followed by the description of the film morphology, structure, and required functionality, master by design rules.
We attempt to describe these properties and show that for a given material, geometry and size of the nanoparticles have a major influence on the electrochemical reactivity and response time. This gives the ability to tune the performance of the film simply by varying the morphology of incorporated nanostructures. This is completed by the recommendations on each major step of an ink formulation, together with imposed critical constraints concerning the fluid control. Finally, the performance of the ink-jet-printed dual-phase electrochromic films is discussed as a case study.
3:15 PM - *ES07.02.05
Dynamic Coloration Using Liquid Crystals
Timothy Bunning 1 , Timothy White 1 , K.M. Lee 1 , Mariacristina Rumi 1 , Vincent Tondiglia 1 , L. de Sio 2 , N. Tabiryan 2 Show Abstract
1 , Air Force Research Laboratory, Beavercreek, Ohio, United States, 2 , BEAM, Inc, Winter Park, Florida, United States
Color can be induced by controlling the real or imaginary part of the refractive index. Dye-doped LC’s or structural mesoscale arrangements of LC molecules lead to systems which can exhibit coloration. Due to their propensity to respond to a variety of stimuli, dynamic coloration properties can be invoked in LC systems. We explore responsive thin films of polymer/liquid crystal and LC/nanoparticle mixtures which exhibit dynamic coloration properties. Various stimuli to induce changes in coloration have been explored including electric and light irradiation. Explored are ‘hidden’ gratings which can be developed with an applied field and novel chiral systems whose macroscopic orientation can be modulated giving rise to a variety of dynamic diffractive effects.
3:45 PM - ES07.02.06
Highly Fluorescent Thiazolothiazole Viologens—Photochemistry, Electrochromism and Photoluminescence
Michael Walter 1 , Alexis Woodward 1 , Kristin Sandor 1 , Joshua Chabeda 1 Show Abstract
1 , University of North Carolina at Charlotte, Charlotte, North Carolina, United States
There continues to be a growing interest in using methyl viologen (MV2+) derivatives for a variety of electrochemical and photochemical applications. It is likely that viologen-based structures with unique multi-functional spectroscopic properties will become important areas of research. We have synthesized a class of viologen structures that demonstrate both reversible electrochromic behavior and high fluorescence quantum efficiency that is deactivated with electrochemical reduction. The thiazolothiazole (TTz2+) viologens exhibit strong blue fluorescence with high quantum yields between 0.8 – 0.96. The TTz derivatives also show distinctive and reversible yellow to dark blue electrochromism at low reduction potentials. The fused bicyclic thiazolo[5,4-]thiazole heterocycle allows the alkylated pyridinium groups to remain planar, strongly affecting their electrochemical properties. The singlet quantum yield is greatly enhanced with quaternarization of the peripheral 4-pyridyl groups (ΦF increases from 0.22 to 0.96) while long-lived fluorescence lifetimes were observed between 1.8 - 2.4 ns. The TTz viologens have been characterized using cyclic voltammetry, UV-visible absorbance and fluorescence spectroscopy, spectroelectrochemistry, and time-resolved photoluminescence. The electrochromic properties observed in solution, in addition to their strong fluorescent emission properties, which can be suppressed upon 2 e- reduction, make these materials attractive for multi-functional optoelectronic, electron transfer sensing, and other photochemical applications.
4:00 PM - ES07.02.07
Dynamic Color Tuning in Polymer Stabilized Cholesteric Liquid Crystals
Kyung Min Lee 1 , Vincent Tondiglia 1 , Timothy Bunning 1 , Timothy White 1 Show Abstract
1 , Air Force Research Laboratory (AFRL), WPAFB, Ohio, United States
Here we report on the dynamic color control in polymer stabilized cholesteric liquid crystals (PSCLCs) by electrically regulated bandwidth broadening, switchable scattering, and red-shifting tuning of the reflection band. The position or bandwidth of the selective reflection of PSCLCs prepared from negative dielectric anisotropy liquid crystalline hosts can be controlled by the application of a direct current (DC) voltage. An electrically regulated color-tunable mirror is demonstrated based on bandwidth broadening of the combined right handed (RH) and left-handed (LH) PSCLCs. Reflection color is controlled from visible wavelength range (red, green, and blue colors) to infrared wavelength (transparent) of the PSCLCs. An electromechanical displacement mechanism involving ion transport leading to the deformation of the template polymer network will be discussed. Color and bandwidth stability, baseline optical properties, and response times are studied. Structural chirality, viscoelastic properties of the polymer network architecture and electro-optic responses will be discussed for the samples prepared in different 365 nm wavelength UV curing conditions and compositions. The electro-optic control of the reflection in these CLCs and PSCLCs could be potentially used in a variety of display technologies and smart windows.
4:15 PM - ES07.02.08
Opto-Nanomechanical Transduction in Photochromic Solid-State Photo-Isomers
Jacqueline Cole 1 2 3 Show Abstract
1 , University of Cambridge, Cambridge United Kingdom, 2 , STFC Rutherford Appleton Laboratory, Harwell United Kingdom, 3 , Argonne National Laboratory, Chicago, Illinois, United States
Crystalline materials that behave as optical actuators and proceed via some form of nano-optomechanical mechanism are of particular interest for optical data storage or quantum computing. Nonetheless, the field is facing a dearth of suitable functional materials for applications. One possible material option is a series of compounds based on the generic formula, [Ru(SO2)(NH3)4X]Y, whose SO2 group manifests solid-state linkage photo-isomerization (X is the trans-ligand to SO2; Y is a counterion). This light-induced phenomenon causes these materials to act as photo-induced molecular switches [3-5] or molecular transducers [6,7] whose nano-optomechanical properties exist in the single-crystal state: a high-quality solid-state medium for single-photon control.
This talk will present the development of this family of materials towards such applications, via a range of advanced ight-induced in situ lmaterials characterization experiments that capture the phenomenon in their light-induced state [8-10]. Results are enabling our understanding of the light-induced molecular structure and nano-optomechanical properties of these light-induced solid-state actuators. Establishing this knowledge-base of structure-to-function relationships leads to the ultimate goal of being able to molecularly engineer these materials for a given device application.
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 A. E. Phillips, J. M. Cole, T. d'Almeida, K. S. Low, Phys. Rev. B 82 (2010) 155118.
 A. E. Phillips, J. M. Cole, T. d'Almeida, K. S. Low, Inorg Chem 51 (2012) 1204.
 S. O. Sylvester, J. M. Cole, Advanced Materials 25 (2013) 3324.
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4:30 PM - ES07.02.09
Photoinduced Effects in Guest-Host Liquid Crystals Containing Naphthopyran Derivatives
Mariacristina Rumi 1 , Timothy White 1 , Timothy Bunning 1 Show Abstract
1 , Air Force Research Laboratory, Wright Patterson AFB, Ohio, United States
Applications of liquid crystals (LCs) often rely on the fact that the properties of a liquid crystalline device can be changed in response to external stimuli, such as temperature, electric field, and light. Guest molecules dispersed in a liquid crystalline material usually affect the order and stability of the system. If the guest molecules undergo a photoinduced transformation, their interactions with the LC environment can be different for the material in the dark and during exposure to light of appropriate wavelength. This can be used to achieve isothermal photoinduced phase transitions (phototropic transitions) and photoinduced changes in other materials properties.
When the guest molecules are naphthopyrans, isothermal phase transitions can occur in which the order in the LC system increases in the exposed state relative to the dark state, in contrast to the more well-known case of azobenzene-based guest molecules or mesogens. The photoinduced changes are attributable to a better compatibility of the naphthopyran photoproduct with the LC host relative to the equilibrium species in the dark. As a consequence, the mesophases are stabilized when the systems are exposed to light. For selected naphthopyran derivatives we have shown that the phase transitions in the LC host 5CB can be shifted to higher temperatures by up to 3 °C and the order parameter increases under exposure to light in the ordered phases of the mixed systems.
We are also investigating the properties of the naphthopyran photoproducts in the LC environment, specifically the efficiency of the photoreaction, the absorption cross sections for transitions into the lowest-lying exited states, and the rates for the thermal relaxation back to the initial species. The naphthopyran thermal relaxation typically follows a single exponential decay, with rates that increase with increasing temperature but that depend on the phase of the LC host. In particular, the activation energy for the thermal relaxation is larger in the ordered phases of the mesogenic solvents 5CB and 8CB relative to their isotropic phase, suggesting that the naphthopyran relaxation is hindered by the organization of the host environment. These results will be useful in building a more complete understanding of the mutual guest-host interactions in naphthopyran-containing LC systems and in the design of multifunctional LC devices triggered by light.
4:45 PM - ES07.02.10
A Complementary Electrochromic Device Composed of Fe(II)-Based Metallo-Supramolecular Polymer and Nanoparticulated Ruthenium Purple
Yen-Chun Wang 1 , Hsin-Che Lu 1 , Li-Yin Hsiao 1 , Kuo-Chuan Ho 1 2 Show Abstract
1 Department of Chemical Engineering, National Taiwan University, Taipei Taiwan, 2 Institute of Polymer Science and Engineering, National Taiwan University, Taipei Taiwan
A novel class of cathodically coloring electrochromic (EC) materials, Fe(II)-based mettallo-supramolecular polymers (Fe(II)-MEPEs) containing iron ions and bis(terpyridine) ligands, have attracted attention for their large optical contrast, fast response time, high coloration efficiency, and outstanding stability. However, due to the relatively high redox potential of the Fe(II)-MEPE thin film, it is essential to find a suitable counter electrode so as to lower the driving voltage of the complementary ECD. In this study, we introduce a nanoparticulated ruthenium purple (RP) thin film, which is purple at the oxidized state, as the counter electrode. Owing to the nanoparticulating process of RP materials, the diffusion resistance of the ionic species inside the RP nanoparticles would be significantly reduced. Therefore, the EC performance of the RP thin film can be enhanced. Since the maximum absorbance peak of RP (at 545 nm) is very close to that of Fe(II)-MEPE (at 580 nm), an complementary ECD based on Fe(II)-MEPE and RP with the synergistic optical change can be constructed. The proposed Fe(II)-MEPE/RP ECD gives a transmittance change of 50.7% at 580 nm when switched between 0 V and 1.3 V. Fast bleaching and coloring response times of 0.4 s were obtained for an ECD with an active area of 1.0 cm x 1.0 cm. Besides, this device remained 90.7% of its initial transmittance change after 1,500 cycles of switching.
Aline Rougier, Institut de Chimie de la Matière Condensée de Bordeaux
Smagul Karazhanov, Institute for Energy Technology (IFE)
John Reynolds, Georgia Institute of Technology
Kazuki Yoshimura, Advanced Industrial Science and Technology (AIST)
ES07.03: Thermochromic I
Tuesday AM, November 28, 2017
Hynes, Level 3, Room 301
8:30 AM - *ES07.03.01
Vanadium Dioxide and Samarium Nickelate Thin Films Synthesized by Pulsed Laser Deposition
Mohamed Chaker 1 Show Abstract
1 , INRS, Varennes, Quebec, Canada
In this presentation, we will focus on the synthesis of metal-insulator transition (IMT) materials using the Pulsed Laser Deposition (PLD) technique that allows an excellent control of material stoichiometry and density as well as of the material nanostructure. Vanadium dioxide (VO2) and samarium nickelate (SmNiO3) are particularly interesting IMT materials as their electrical resistivity as well as their infrared and terahertz (THz) reflectivity undergo significant changes across the thermo/photo-induced IMT, at transition temperatures TIMT ≈ 68°C for VO2 and 110-133°C for SmNiO3. In a series of investigations, our group has examined the physics governing the IMT of VO2 and SmNiO3 thin films and has explored new application opportunities including uncooled bolometers, and smart radiator devices for space applications.
The IMT properties of VO2, namely the transition temperature, the sharpness of the transition, the amplitude of the properties modification and the related hysteresis width, can efficiently be tailored through doping with an appropriate concentration of donors and/or acceptors and through a proper control of crystallinity, morphology and stoichiometry of the VO2 films. In order to fully exploit this material for IR and THz applications, we first studied the effect on the IMT characteristics of both W-doping and oxygen pressure (PO2) during the growth of VO2 thin films synthesized by pulsed laser deposition. In this way, we were able to develop a new type of energy-efficient, light-weight, and high-performance variable-emittance coatings based on VO2 thin films (smart radiator device) that can passively control the internal temperature of nano-satellites. Second, we propose a WxV1-xO2 multilayer structure (MLS), with a bottom-up gradient of tungsten content, which displays a combination of excellent electrical characteristics and presents a great potential for the development of highly responsive sensing layers in energy-efficient uncooled microbolometer. Finally, we demonstrate that the control of PO2 during the synthesis of VO2 films is one of the key parameter to tailor their IMT features for specific applications in the THz range, such as sensor-type and memory devices.
We also overview our recent studies on the synthesis of SmNiO3 thin films by PLD. We examine the influence of epitaxial strain on the structure, electronic transport and optical properties of epitaxial SmNiO3 thin films grown on LaAlO3 (LAO, compressive) and SrTiO3 (STO, tensile). As the strain changes from tensile to compressive, the transition temperature of the SmNiO3 samples shifts to lower temperatures. The optical conductivity reveals the strong dependence of the Drude spectral weight on the strain relaxation.
9:00 AM - ES07.03.02
Insulator–Metal Transition in Substrate-Independent VO2 Thin Film for Phase-Change Devices
Mohammad Taha 2 1 , Sumeet Walia 2 1 , Taimur Ahmed 2 1 , Daniel Headland 3 , Withawat Withayachumnankul 3 , Sharath Sriram 2 1 , Madhu Bhaskaran 2 1 Show Abstract
2 , Functional Materials and Microsystems Research Group and Micro Nano Research Facility, Melbourne, Victoria, Australia, 1 , RMIT University, Melbourne, Victoria, Australia, 3 School of Electrical and Electronic Engineering, The University of Adelaide, Adelaide, South Australia, Australia
Vanadium oxides display interesting switching properties such as their ability to undergo electrical switching from an insulator to a metal, which is accompanied by a shift in optical properties of the metal oxides. With the binary VO2 presenting stimuli-dependent phase transitions that manifest as switchable electronic and optical features. An elevated temperature induces an insulator–to–metal transition (IMT) as the crystal reorients from a monoclinic state (insulator) to a tetragonal arrangement (metallic). This transition is accompanied by a simultaneous change in optical properties making VO2 a versatile optoelectronic material. VO2 is favoured when it comes to the interest of many researchers due to its close to room temperature transition, which occurs at around ~68 degrees Celsius. However, its deployment in scalable devices suffers because of the requirement of specialised substrates to retain the functionality of the material. Here, we address this major challenge in harnessing the functionality in VO2 by demonstrating an approach that enables crystalline, switchable VO2 on any substrate. Glass, silicon, and quartz are used as model platforms to show the effectiveness of the process. Temperature-dependent electrical and optical characterisation is used demonstrating three to four orders of magnitude in resistive switching, >60% chromic discrimination at infrared wavelengths, and terahertz property extraction. This capability will significantly broaden the horizon of applications that have been envisioned but remained unrealised due to the lack of ability to realise VO2 on any substrate, thereby exploiting the untapped potential of this material This process allows incorporation of high-performance IMT in VO2 on any substrate, independent of the substrate crystallinity and orientation.
9:30 AM - ES07.03.04
A Facile Top-Down Synthesis Method of VO2(M) Nanoparticles for Thermochromic Smart Window Application
Youngkwang Kim 1 , Sangbae Yu 1 , Jinsoo Ahn 2 , Junwoo Son 1 Show Abstract
1 MSE, Pohang University of Science and Technology, Pohang Korea (the Republic of), 2 , Research Institution of Industrial Science and Technology, Pohang Korea (the Republic of)
Youngkwang Kim1), Sangbae Yu1), Jinsu Ahn2) and Junwoo Son1)
1) Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Republic of Korea
2) Research Institute of Industrial Science and Technology (RIST), Pohang 37679, Republic of Korea
Thermochromic smart window have received extensive interests and demands for the application of current energy and environment applications. In particular, VO2(M) nanoparticles has been extensively studied and developed over the past ten years as thermochromic smart window application due to the tunable infrared absorption near metal-insulator transition(MIT) temperature at 68 C. However, most of the preparation methods for the synthesis of VO2(M) nanoparticles, such as hydrothermal, sol-gel etc. are not suitable for practical use because of their high cost, multiple steps reaction and small scale issues.
In this presentation, we report a facile, cost-effective but large-scale commercially available preparation method of VO2(M) nanoparticles by nano-bead milling and thermochromic films by tape-casting. First, bead milling technique was utilized for grinding micro-sized V2O5 powder down to ~ a few tens of nm. Due to the small size of V2O5, highly pure and uniform VO2(M) nanoparticles can be obtained without any compositional variation down to the size of ~38 nm by only one-step annealing reaction. The latent heat across the phase transition was measured to be ~28 J/g, which represents the high crystallinity of as-synthesized VO2(M) nanoparticles. Furthermore, the film prepared by tape-casting showed the IR reduction at 1992 nm across MIT was calculated to be ~33.23%, which is comparable to the best films prepared from hydrothermal methods. Our method will open up a facile way to efficiently produce thermochromic powder and films, leading to the commercialization of VO2-based thermochromic smart window.
9:45 AM - ES07.03.05
Thermochromic Multilayer Films of VO2/TiO2, VO2/ZnO VO2/SnO2 and VO2/WO3 for Energy Efficient Windows
Isil Top 3 , Russell Binions 3 4 , Isaac Abrahams 4 2 Show Abstract
3 School of Engineering and Materials Science, Queen Mary University of London, London United Kingdom, 4 Materials Research Institute, Queen Mary University of London, London United Kingdom, 2 School of Biological and Chemical Sciences, Queen Mary University of London, London United Kingdom
Vanadium dioxide (VO2) is a thermochromic material which changes its optical properties upon passing through a critical transition temperature (Tc) of 68 °C which is still too high and needs to be lowered to the proximity of room temperature.The strong yellow colour and low luminous and visible light transmittance is a significant obstacle to employ these films for windows coatings applications. During the deposition of VO2 thin films, electric fields are applied. It was observed that, when the field strength increased, the crystallite size of the VO2 samples were lowered, by reducing the Tc. However, the films became more prone to oxidization to non-thermochromic V2O5 upon the thermal cycling. Also, the plain VO2 films can be scratched by a scalpel. Therefore protective antireflective top layer films of TiO2, ZnO and SnO2 and WO3 were coated.
Nanostructured VO2 bottom layers were deposited by AACVD using DC and AC voltages, with field strengths varying from 200 V m-1 to 1500 V m-1 at 430 °C on fluorine doped tin oxide glasses. The plain VO2 films were yellow/brown in colour; while top layers introduced different colours which improved the aesthetic appearance of the films. Compared to plain VO2 films, multi-layered films had superior thermochromic properties and exhibited a stronger adherence to the substrate, compared to plain VO2 films as determined by the adhesive-tape peel test and could not be scratched by a scalpel. Introduction of additional layers resulted in a dramatic increase in the visible light transmission (Tvis) by up to 30 % compared to a plain VO2 sample. VO2/TiO2 bilayer films showed a higher transmittance modulation (DT) in the near infrared of up to 20 % compared to bare VO2 films upon the thermochromic transition. TiO2 top layers induced light pink colour. VO2/ZnO films were formed of nanoparticles, and exhibited an enhanced Tvis of 70% and DT of 25 % with narrower hysteresis loop width and lower Tc of ∼45 °C. Comparable results were obtained for production of SnO2 top layers which offered porous nanocrystalline nanostructure with Tvis of 65%, DT of 25% of Tc of ∼55 °C. VO2/WO3 exhibited the highest DT of 35 %, with Tc of ∼50 °C, and changed the film colour to light white. VO2/TiO2 bilayer films had multifunctional properties combining thermochromic properties and self-cleaning behaviour when exposed to UV light. After 30 min irradiation, 50 % of the stearic acid destroyed, while upon 120 min UV irradiation, the complete destruction of stearic acid was observed.
Keywords: Thermochromics, thin films, vanadium dioxide, aerosol assisted chemical vapour deposition, titanium dioxide, zinc oxide, tin dioxide, tungten trioxide, self-cleaning.
10:30 AM - *ES07.03.06
Thermo- and Piezo-Chromic AMoO4 Oxides
Manuel Gaudon 1 Show Abstract
1 , ICMCB CNRS, Pessac France
Without presuming of the reversible or irreversible character of the phenomenon, X-chromic materials may be defined as compounds whose color changes with an external stimulus. Namely, thermochromism and piezochromism refer to the ability of a material to change color with the temperature or the external pressure.
Our oral presentation will focus on the CuMoO4 [1-5] and CoMoO4 [6,7] X-chromic materials. These molybdates exhibit an abrupt color modification due to a severe structural rearrangement associated to a first order transition which can be produced by pressure, temperature or surface protonation . Indeed, for both oxide families, the high temperature / low pressure modifications exhibit [MoO4] tetrahedra while the low temperature / high pressure modifications exhibit [MoO6] octahedra.
Two ways can be used in order to tune the thermochromic transition temperature and or the piezochromic transition pressure: (i) the doping or substitution of the (Cu/Co)MoO4 oxide with various transition metals (Fe, Mg, Ni, Zn…) [1,4, 5,7], (ii) the control of the oxide morphology, especially its crystallite size . It can be also added, that for the piezochromism phenomenon, the application mode of the pressure (isostatic, uniaxial) significantly affects the pressure answer of these materials [5,6]. The results of the chemical/morphological impacts on the transition parameters will be discussed basing on the fundamentals of first-order phase transition thanks to X-Ray/Neutron diffraction, magnetic measurements, Mossbauer spectroscopy (on the FeMoO4 based compounds), in-situ optical characterizations, and microscopic observations...
Finally, it will be shown that nowadays, such materials receive attention due to their potential applications as convivial temperature/pressure indicators, especially in the areas of safety/security improvements, gadgets, packaging, motorization, autoclaves…and especially while the oxide powder is incorporated into a paint/varnish, for the shock detection on fragile substrates.
1. M. Gaudon et al, Advanced Materials, 19, 3517-3519, 2007.
2. M. Gaudon et al, Inorganic Chemistry, 48, 2136-2139, 2009.
3. A.-E. Thiry et al, Chemistry of Materials, 20, 2075-2077, 2008.
4. M. Gaudon et al, Inorganic Chemistry, 46, 10200-10207, 2007.
5. V. Blanco-Gutierrez et al, Dalton Trans., 42, 47-53, 2013.
6. L. Righetti et al, ACS Appl. Mater. Interfaces, 3, 1319-1324, 2011.
7. L. Robertson et al, Inorganic Chemistry, 50, 2878-2884, 2011.
8. M. Gaudon et al, Chemistry of Materials, 22, 5905-5911, 2010.
11:00 AM - ES07.03.07
Co-Doped Quarternary Thermochromic V1-x-ySrxWyO2 Thin Films and Their Properties in Optimized Multilayer Systems for Smart Windows
Florian Kuhl 1 2 , Angelika Polity 1 2 , Peter Klar 1 2 Show Abstract
1 Institute of Experimental Physics I, Justus Liebig University, Giessen Germany, 2 Center for Materials Research (LaMa), Justus Liebig University, Giessen Germany
For smart window applications the well known thermochromic transition of VO2 from semiconductor to metal is a promising candidate for active window glazings. The phase transition from a monoclinic to a tetragonal structure at about 68 °C in bulk material leads to a reduction of the optical transmittance in the near infrared, thus the incoming radiation heat could be blocked to passively control the temperature inside a building. Undoped VO2 does not fulfill the required parameters for application as window glazing such as transition temperatures in the range of Φc ≈ 25 °C, solar transmittance Tsol ≈ 40 % and luminous transmittance Tlum > 40 % as well as a sufficiently large band gap to yield a neutral color impression.
With the technique of co-doping during the sputter deposition we demonstrated that simultaneous presence of W or F and an alkaline earth metal like Sr decreases, on the one hand, the transition temperature down to values about 20 °C and lower. On the other hand, the optical properties could be improved, i.e. ΔTsol already is about 5% close to the required value of ΔTsol = 10%. The color impression is neutral.
We present multilayer systems with a buffer layer for better cristallinity of the functional quarternary layer and an antireflective layer for enhancing the optical properties. Samples were prepared by sputtering on different substrates. The thin films were characterized as single layers first and afterwards as whole multilayer system via UV-VIS-NIR transmittance measurements at different temperatures. Switching behavior at a distinct wavelength in the IR range can be determined by hysteresis measurements of the transmittance and the optical properties are calculated based on the transmittance measurements.
11:15 AM - ES07.03.08
Interdependence of Structure, Morphology and Phase Transitions in CVD Grown VO2 and V2O3 Nanostructures
David Graf 1 , Lisa Czympiel 1 , Sanjay Mathur 1 Show Abstract
1 , University of Cologne-Inorganic Chemistry, Cologne Germany
Phase selective chemical vapor deposition of nanostructured vanadium dioxide (VO2) and sesquioxide (V2O3) was achieved by deploying [V(OR)4]n (R = tBu, n = 1 (1), R = Et, n = 3 (2), R = Me, n = 4 (3)). Use of [V(OtBu)4] (1) produced thin films of monoclinic VO2 (M1) at 700 and 800 °C consisted of anisotropic nanostructures with high crystallinity and small hysteresis in the metal-to-semiconductor transition (MST). Film morphologies manifested strong dependence on growth temperatures and exhibited pronounced texturing effects at high temperatures (>700 °C). The microstructure of the films was found to significantly affect the MST behavior of VO2 films. DTA measurements of VO2 films showed MST at 63 °C (700 °C) and 65 °C (800 °C), much lower than the transition temperature observed in single crystal material (68°C). Variable-temperature transmission UV/vis spectroscopy displayed a strong interdependence between microstructure and light transmission. Precursors were characterized in the solid-state (XRD) and solution-state (temperature depended EPR, NMR) to reveal an association-dissociation equilibrium in solution (complex 2 and 3), involving monomeric, dimeric and oligomeric species. Use of 2 and 3 as single precursors produced thin films of crystalline V2O3 consisting of nanosheets (5 nm) with a flower-like morphology. Preliminary electrochemical performance investigation presents superior behavior for supercapacitors application.
11:30 AM - ES07.03.09
High Throughput Characterization of Transition Temperatures and Lattice Parameters in Thermochromic Lightly Substituted VO2
Sara Barron 1 , Nam Nguyen 1 , Winnie Wong-Ng 1 , Martin Green 1 Show Abstract
1 , National Institute of Standards and Technology, Gaithersburg, Maryland, United States
Vanadium dioxide exhibits a well-known metal to insulator transition as the material is cooled to 68 °C, with a concurrent thermochromic transition from near infrared (NIR) reflective to transparent. Building windows with a coating of VO2-based materials allow zero-power smart control of heat transfer. Namely, on cold days, when the ambient temperature is below the coating’s transition temperature, the window coating is transparent to NIR solar radiation; conversely on hot days, the window coating reflects the NIR solar radiation. Both effects reduce the energy load on the building’s heating and cooling systems. Dopants are thought to be required for VO2 viability for these applications. Large, electron-rich dopants, such as W6+, are needed to depress the thermochromic transition temperature to Earth ambient temperatures. Other dopants such as Mg2+ are shown to increase the transparency in the visible spectrum, thereby maintaining the aesthetic appeal of building windows. We report the results of a high throughput analysis of the thermochromic transition in lightly substituted VO2. High throughput tools are invaluable as a first screen of relevant materials properties to efficiently cover the broad materials composition space of VO2 with one or more other metal cations. Thin film libraries of V1-x M xO2, with 02O5 and one or more unary metal oxide targets. We have built a high throughput thermochromic measurement system, made up of an x-y translation stage, a thermoelectric heater/chiller with temperature control in the range of 5 °C to 90 °C, and a fiber optic-coupled NIR spectrometer. The results from a single wafer combinatorial library of, e.g., V1-x MoxO2, are 8085 NIR reflectance spectra, collected from 165 different V1-x MoxO2 compositions at 49 different temperatures. From this data, a thermochromic transition temperature can be determined for each of the 165 different compositions represented. To characterize the effects on the complex index of refraction in the visible spectrum, the spectrometer can be replaced with a fiber-optic coupled visible spectrometer. We couple the thermochromic optical results with interatomic spacings from x-ray diffraction. The d-spacing for the prominent (011) rutile-type VO2 is found to be indicative of the transition from the low temperature monoclinic phase to the high temperature tetragonal phase. Covering a wide swath of metal dopants, we find the depression of transition temperatures occurs with increasing substitution of electron rich atoms such as W or Mo, but also more generally occurs with increasing (011) d-spacing. Finally, we show that the high compositional density of our characterizations (reflectance, lattice parameter, composition), even when only at room temperature, allows the identification of material compositions exhibiting transitions near room temperature.
ES07.04: Conjugated Polymers
Ben Zhong Tang
Tuesday PM, November 28, 2017
Hynes, Level 3, Room 301
1:30 PM - *ES07.04.01
Bistable Electrochromism in Conjugated Polymer Based Electrochromic Devices
Eunkyoung Kim 1 Show Abstract
1 , Yonsei University, Seoul Korea (the Republic of)
The optical memory at voltage-off states (V-Off) is important for energy saving electrochromic windows and electrochemical displays. Optical memory at both colored and transparent states under V-Off, called bistability, should be compulsory for a large area electrochromic device (ECD), because no additional energy consumption is required to maintain the colored or transparent state. To achieve long bistability in an ECD, we attempt to control the spontaneous electron and ion transfer between the interfaces of conjugated polymer (CP) films. First, interfacial dopant ion transport (IDT) was controlled by using ionic liquids, which form ion blocking layers through electrochemical double layer. Next, the effect of the redox potential of polymers on optical memory was examined to control the interfacial electron transfer (IET) between an electrode and CP films, by using CPs of different HOMO energy levels. Finally charge balancing between the electrodes was boosted using a non-electrochromic charge balancing layer (CBL), to afford an electrochromic window with high color contrast, coloration efficiency, and long EC cyclability. Herein material combination based on IDT, IET, and CBL will be proposed to attain a bistable and autonomous ECD.
2:00 PM - ES07.04.02
Making a Big Difference through Small Changes—Tuning Electrochromic Properties of Conjugated Polymers through Subtle Structural Modifications
Anna Österholm 1 , Eric Shen 1 , James Ponder 1 , Michel de Keersmaecker 1 , John Reynolds 1 Show Abstract
1 , Georgia Institute of Technology, Atlanta, Georgia, United States
As color changing materials, conjugated polymers have the advantage that simple synthetic modifications can have a large impact on their optical and electrochemical properties. We have exploited this versatility to acquire a family of cathodically coloring electrochromic polymers that span the entire visible spectrum. Traditionally, color control in dioxythiophene-based polymers (XDOTs) was achieved through inducing large changes in dihedral angle between repeat units through steric interactions, while the substitution pattern beyond the oxygen atoms was believed to have little effect on the redox and electronic properties. Here, we will begin by showing how subtle differences in aromaticity, planarity, and electron density of the heterocycle can be used to tune the color, redox properties, and switching times in a family of XDOT-based copolymers. For instance, replacing the sulfur atom in the thiophene ring with a larger selenophene, gives rise to a much lower onset of oxidation and red-shifted absorbance profile for these copolymers. On the other hand, altering the electron density, but maintaining the steric bulk of the one of the copolymer repeat units affords a simple way to tune redox properties while maintaining the desired color. Finally, we will demonstrate how the functional groups located far from the conjugated backbone, long thought to only impact solubility, can also be used to tune electrochromic properties and how something as simple as adding a branching point or a few oxygen atoms to the side chain can drastically affect material performance.
2:15 PM - ES07.04.03
A General Method for Getting Gasochromic Phenomena from Electrochromic Polymers
Chih-Wei Hu 1 , Yasusei Yamada 1 , Kazuki Yoshimura 1 Show Abstract
1 , National Institute of Advanced Industrial Science and Technology (AIST), Nagoya Japan
We report the first observation of gasochromism for a material based on thin films of electrochromic polymers:polyaniline:polystyrene sulfonate/platinum nanoparticles (PANI:PSS/PtNPs) and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate/platinum nanoparticles (PEDOT:PSS/PtNPs). These novel materials display a significant colour change, PANI:PSS/PtNPs show from green to pale yellow and PEDOT:PSS/PtNPS show from transparent to blue, when they exposed to hydrogen gas. The color changes are similar to their electrochromic characters when undergo redox reactions. Our results show that the PtNPs trigger a reductive reaction on the polymer surface. This new mechanism dramatically expands the selection of available gasochromic materials.
2:30 PM - ES07.04.04
Color Control in Cathodically Coloring and Anodically Coloring Conjugated Organic Electrochromics
Dylan Christiansen 1 , John Reynolds 1 Show Abstract
1 , Georgia Institute of Technology, Atlanta, Georgia, United States
Electrochromism is the change of a material’s color upon the application of an electrochemical potential. These materials have prospective uses in full color passive displays, energy saving tinted windows, and dimmable visors for military and/or recreational use. Organic polymer electrochromes have the benefits of being solution processable, lightweight, and flexible. The absorbances of the neutral and oxidized states of these materials are synthetically straightforward to control through heterocycle choice, electron richness, steric strain, and copolymerization. This work compares and contrasts the methods of controlling absorption characteristics in both anodically coloring and cathodically coloring conjugated organic electrochromic materials.
Among cathodically coloring materials, conjugated polymers have been synthesized that cover the visible spectrum. While thousands of switches have been demonstrated for colors such as magenta and blue, the challenge in this family of materials is creating stable wide band gap systems (yellows, oranges, and reds). Here, we show that using sterically bulky phenylenes as comonomers with dioxythiophenes (DOTs) give the ability to incorporate larger portions of electron rich DOTs while maintaining wide band gaps. We also show that reducing the electron density along the conjugated backbone by replacing the alkoxy substituents with an alkyl chain allows for widening the band gap. Both of these approaches have led to yellow, orange, and red electrochromic polymers that have significantly improved switching stabilities over the previous generations.
In contrast, anodically coloring organic electrochromic materials are discrete chromophores that are UV absorbing in the neutral state which upon oxidation form broadly absorbing, colored radical species. While efforts in cathodically coloring systems have been focused on tuning the neutral state absorbance, in anodically coloring systems color control is achieved by controlling the singly occupied molecular orbitals (SOMO). Here we introduce novel UV absorbing discrete chromophores based on a 2-thiomethyl-dioxythiophene coupled to a 4-methoxyphenylene. We show that SOMO control is achieved by readily tuning the substitution pattern on the phenylene moiety, leading to radical cations that absorb across the visible spectrum.
ES07.05: Thermochromic II
Tuesday PM, November 28, 2017
Hynes, Level 3, Room 301
3:30 PM - *ES07.05.01
Sunlight Responsive, Continuously Variable Thermochromic Materials for Dynamic Windows
Harlan Byker 1 , Christopher Anderson 1 , Samuel DeJong 1 Show Abstract
1 , Pleotint, LLC, West Olive, Michigan, United States
Ligand exchange thermochromic, (LETC), materials incorporated into a polyvinylbutyral interlayer are finding wide spread use in self-tinting, dynamic windows. These windows maximize daylighting while minimizing solar heat gain by tinting to a level dependent on the intensity of sunlight directly on the window. The heat of the sun is used to darken the window and block the heat of the sun when there is direct sun and the windows clear up to provide daylighting when sunlight is indirect. No wires, power supplies or controls are required. The addition of near infrared absorbing nanoparticles to the thermochromic interlayers provides enhanced sunlight repsonsiveness to the point where monolithic windows for buildings and transporation markets are being considered.
4:00 PM - ES07.05.02
Thermochromic Coatings and Nanocomposites for Smart Adaptive Glazing
Luc Leufkens 1 2 , Ryan van Zandvoort 1 2 , Ralph Stevens 1 2 , Zeger Vroon 1 2 , Pascal Buskens 1 2 , Aike Wypkema 1 2 , Jessica Rodríguez-Fernández 1 2 Show Abstract
1 , Brightlands Materials Center, Geleen Netherlands, 2 Materials Solutions Department, TNO (Netherlands Organization for Applied Scientific Research), Geleen Netherlands
The ambitious energy goals of the ‘Paris Agreement’ to reduce global warming are driving cities and regions to become energy neutral. The building sector is one of the most energy-demanding sectors, both in the US and Europe and, therefore, addressing energy-saving approaches in this area is a major need in order to accomplish energy neutral human settlements. At the Brightlands Materials Center, a new R&D and innovation center located at the Chemelot Campus in Geleen (The Netherlands), we are working toward increasing the energy efficiency of buildings by reducing their energy consumption through materials solutions that address the building envelope, which is the primary thermal barrier between the interior and the exterior of a building. We carry out this work in close collaboration with industrial partners in the framework of our Sustainable Buildings Program, where we target both the transparent (glass windows) and non-transparent (façades) components of building envelopes.
In this presentation I will focus on the transparent building envelope. Specifically, I will give an overview on our latest developments on coatings and nanocomposites based on thermochromic materials. For instance, state-of-the-art thermochromic coatings are typically multilayer coatings prepared by sputtering methods, characterized by a ca. 40% transmission in the visible range, and by a significant yellowing as well. These latter two aspects significantly limit their applicability in glazing. In contrast, the thermochromic coatings that will be featured in this presentation are single layer coatings that are obtained by wet-chemical methods and that feature a transmission in the visible of up to 70% along with color neutrality. It will be discussed how a thermal stimulus can trigger changes in the optical response of such coatings and related nanocomposites and how those optical changes translate into an energy-saving benefit upon deployment in glass windows. Overall, this presentation will showcase the added value of our thermochromic coatings and nanocomposites, thus illustrating the competitive advantage of static vs. smart, adaptive, glazing.
 U.S. Energy Information Administration (EIA), 2012.
 Eurostat, 2014.
4:15 PM - ES07.05.03
A TiOx-Based, Visible-to-Infrared Broadband Electrochromic Material for Thermal and Optical Management
Jyotirmoy Mandal 1 , Yuan Yang 1 Show Abstract
1 , Columbia University, New York, New York, United States
Visible-to-infrared electrochromic materials have a great potential for use in a wide array of applications, which range from smart windows and flexible displays, to visible-to-infrared optical camouflaging and thermal management. However, compared to visibly electrochromic materials, relatively few materials that exhibit such broadband electrochromism are known, and their potential applications related to optical and thermal management remains to be investigated in detail. [1-2]
Here, we report a TiOx-based, fast-switching electrochromic material that exhibits tunable, broadband emissivity from the visible to the infrared wavelengths. Multilayer architectures based on the material have emissivities that are electrochemically tunable by ~ 0.74 in the solar wavelengths (0.35-2.5 μm), and ~0.68 and ~0.30 in the mid-wave infrared (MWIR, 3-5 μm) and long-wave infrared (LWIR, 8-13 μm) wavelengths. Furthermore, the TiOx based material is shown to be highly stable, and retains its optical performance over a large number of electrochemical cycles.
We further show experimentally that the large optical tuneability of the TiOx-based material can be used for thermal camouflaging and switchable radiative heat-management. Given the material's stability over large number of cycles, the demonstrated uses make the material highly promising for optical and thermal management applications.
 H. Li, K. Xie, Y. Pan, M. Yao, C. Xin, Synthetic Metals 2009, 159, 1386.
 A. Rougier, K. Sauvet, L. Sauques, Ionics 2008, 14, 99.
4:30 PM - *ES07.05.04
Chromogenic Materials and Devices with Aggregation-Induced Emission Characteristics
Benzhong Tang 1 Show Abstract
1 , Hong Kong University of Science and Technology, Hong Kong Hong Kong
Aggregation-induced emission (AIE) has attracted continuously growing attention for its great potential in material science and biological techniques to conquer the notorious aggregation-caused quenching (ACQ) effect. Our recent studies have demonstrated that it is feasible to construct the solid-state chromogenic materials with high photoluminescence efficiency up to unity by melting AIEgens with conventional luminescent materials that suffer from ACQ problem at the molecular levels. On the other hand, organic electronic devices, such as organic light-emitting diodes (OLEDs) with tunable electroluminescence colors from blue to red and excellent efficiencies approaching theoretical limit can also be easily-fabricated without complicated doping method when using AIEgens as the light-emitting materials. Additionally, rational modifications on AIEgens with carrier-transporting functional groups can endow the luminescent materials with good hole- or electron-transporting abilities. By utilizing these multifunctional materials as light-emitting and hole-transporting (electron-transporting) simultaneously, the non-doped bilayer OLEDs can afford remarkably high efficiencies. These results clearly manifest the practical utility of the AIE effect in the development of chromogenic materials and devices.
ES07.06: Poster Session
Wednesday AM, November 29, 2017
Hynes, Level 1, Hall B
8:00 PM - ES07.06.02
Photo-Controllable Reflection Band Tuning and Broadening in Polymer Stabilized Cholesteric Liquid Crystals
Kyung Min Lee 1 , Vincent Tondiglia 1 , Timothy Bunning 1 , Timothy White 1 Show Abstract
1 , Air Force Research Laboratory, Wpafb, Ohio, United States
We have recently reported on dynamic electro-optic (EO) responses in the polymer stabilized cholesteric liquid crystals (PSCLCs) including bandwidth broadening, switchable scattering, and red-shifting tuning of the reflection band. The position or bandwidth of the selective reflection of PSCLCs prepared from negative dielectric anisotropy liquid crystalline hosts can be controlled by the application of a direct current (DC) voltage. Here, we report that these EO responses of PSCLCs can be further controlled by 365nm wavelength UV light (photosensitive). The photosensitivity is explained by the increased ion density during irradiation with UV light of a series of control liquid crystal (LC) compositions. The ion density in the LC mixtures depends upon type and the concentration of the photoinitiators (Irgacure 369 vs. Irgacure 651). Thus, the magnitude of the electrically tuned or broadened reflection band of PSCLC of certain compositions is further increased in the presence of UV light when subjected to constantly applied DC voltage.
8:00 PM - ES07.06.03
Rapid and Facile Detection of Hydrogen Sulfide Gas Using Silver Nanorods Array
Shashank Gahlaut 1 , Kavita Yadav 1 , J P Singh 1 Show Abstract
1 , Indian Institute of Technology Delhi, Delhi India
Here, we have demonstrated a novel approach for fast and selective detection of H2S gas using silver nanorods at room temperature under ambient conditions. The silver nanorods were prepared by using glancing angle deposition system. We have found that the water wetting properties of silver nanorods sample and its color were highly sensitive towards the silver sulfurization in presence of H2S gas with a gas concentration in parts per million (ppm) range. The reaction on the silver nanorods surface in presence of H2S gas proceeded very quickly as indicated by the change in contact angle and colorimetric results. The observations reveals that the initial chemical reaction rate on silver nanorods surface in presence of H2S gas was proportion to gas concentration and exposure time. The performance of silver nanorods as H2S gas sensor in ambient condition is represented by its sensing ability of 5ppm of H2S gas with exposure time of only 30 seconds. It was found that the contact angle method is superior to colorimetric method because after 30s exposure of H2S gas, we have observed a remarkable change in contact angle however there was no significant change in color of sample observed. We have also compared these results on silver thin film and proved the nanorods highly sensitive over thin film. In this report, we have also demonstrated the detection of H2S emission from aged wool fabric by silver nanorods in air ambient without any exposure of ultraviolet light. The high sensing ability of silver nanorods may have potential application in art conservation.
8:00 PM - ES07.06.04
Effects of Applied Voltage on the Long-Term Stability of Electrochromic P3HT Films
Tae-Ho Kim 1 , Yoon-Chae Nah 1 Show Abstract
1 , Korea University of Technology and Education, Cheonan Korea (the Republic of)
Electrochromism refers to a reversible optical change of materials during electrochemical reactions. As an active system to control the intensity of color or opacity by working purpose of users, electrochromic (EC) devices are distinguishable from other passive chromogenic devices such as thermochromic, photochromi, and gasochromic devices, etc. In principle, EC devices can be operated by applying only a few volts compared to other optoelectronic devices and in particular, they can maintain their colors for some time under open circuit conditions (so-called memory effect). Because of these advantages, EC devices has been studied for applications in smart window, switchable mirrors, information displays, and optical shutters.
Among EC materials, electrochemically active conjugated polymers such as polythiophene, polyaniline, polypyrrole, and their derivatives have received much attention due to their high switching speed, multiple coloration, and lower working voltage. However, a cycle stability of these materials under electrochemical conditions has been a challenging issue to develop the next generation of EC devices. Efforts to prolong EC cyclability have intensively been exploited via incorporation of functional materials in electrodes or electrolytes. However, it is most important to adjust a driving voltage carefully to attain a sufficient stability during electrochromic reactions. Unreasonable applications of voltage can cause an irreversible electrochemical reaction which leads to poor stability of EC materials. In this paper, the effects of voltage range and retention time on EC reactions were investigated using poly (3-hexyl thiophene) (P3HT). We observed that a stable long-term cyclability of P3HT films was achieved by optimization of these voltage conditions. Furthermore, due to a stable optical memory, voltage retention time could be controlled during EC reactions, which results in a reduction of power consumption by about 10 %.
8:00 PM - ES07.06.05
A Complementarity Type Electrochromic Device with Prussian Blue and WO3 Using Wet Processes
Kazuki Tajima 1 , Hiroshi Watanabe 1 , Mizuka Nishino 1 , Tohru Kawamoto 1 Show Abstract
1 , AIST, Tsukuba Japan
Electrochromic materials are expected to be implemented into color-switchable smart windows for energy saving. Electrochromic thin film in the smart windows are often made by a batch process using magnetron sputtering. Recently, United States Department of Energy (DOE) said that promising research using novel materials with low cost manufacturing processes such as solution-based process may also have potential to dramatically reduce costs of the smart window fabrication. DOE also expects high-contrast ECDs, e.g high transmission probability > 60 % in fully transparent state and a very low transmission in the darken state .
Previously, we developed electrochromic device (ECD) with water-dispersible nanoparticles of Prussian Blue (PB) analogues with wet process, where the zinc hexacyanoferrate (ZnHCF), which keeps colorless during its redox reaction, has been used for the counter electrode. In the PB/ZnHCF type ECD, the film becomes thicker to raise the contrast, although thinner film is preferable to improve the device stability and response speed. For the high contrast ECD with thinner film, we developed the wet-processed complementary type ECD with the combination of water dispersible nanoparticles of PB and WO3, where the oxidation-reduction reaction between PB and WO3 is inverse reaction.
The PB and WO3 thin films were coated on ITO/glass substrate using aqueous nanoparticle ink. The final structure of the ECD was a glass / ITO / PB / electrolyte / WO3 / ITO / glass. Although the thickness of the PB thin film was as very thin as about 150 nm, the ECD showed the absorbance of 2 at the wavelength of around 700 nm in the colored state.
 QUADRENNIAL TECHNOLOGY REVIEW, DOE, 2015
8:00 PM - ES07.06.06
Highly Flexible Electrochromic Devices Using Transparent Polyimide Film
Youngseok Kim 1 , Jieun Lee 1 2 , Kuk Young Cho 2 Show Abstract
1 , KETI, Seongnam-si Korea (the Republic of), 2 , Hanyang University, Ansan-si Korea (the Republic of)
Electrochromic (EC) materials reversibly alter their optical properties such as absorbance and transmittance. Due to the light control and energy-saving properties, electrochromic devices have been employed for numerous applications, including car-mirror, reflective display, and sensors. The structure of electrochromic device is composed of two substrate, two transparent conductive layer and electrochromic mixture. This electrochromic mixture is composed of all the electroactive materials (electrolyte, electrochromic and ion storage material) needed for acts as an electrical contact between the electrode and EC materials. Recently, interest in flexible devices has increased, but there is a problem of substrate contact during bending, so it is important to maintain a gap between substrates during bending. However, solid based EC materials such as tungsten oxide are inconsistent for flexible device due to high processing temperature and brittleness.
Herein, viologens-based electrochromic devices (ECDs) were fabricated utilizing ferrocene (Fc) as a redox mediator and ethylene/propylene carbonate as organic solvent. Colorless polyimide film was used as separator to minimize the leakage problems and maintain the gaps during bending. In addition, highly flexible characteristics were obtained with flexible electrodes based on a percolated network of silver nanowires (AgNWs). Flexible electrochromic devices fabricated from polyimide separator with absorbable electrochromic materials and silver nanowires exhibit stable performance under mechanical and thermal stresses.
8:00 PM - ES07.06.07
Comparison of Two Cost-Effective Synthesis Routes to Prepare Highly Crystallized VO2 (M) and Its Doping
Shian Guan 1 , Issam Mjejri 1 , Nicolas Penin 1 , Aline Rougier 1 , Manuel Gaudon 1 Show Abstract
1 , CNRS ICMCB, Pessac France
Among thermochromic materials for energy efficient applications, vanadium dioxide (VO2) has sparked immense interest all over the world, due to its low metal-insulator transition (MIT) temperature (Tc = 68 °C) associated with a structural change in-between monoclinic VO2 (M) and rutile phase VO2 (R). While the many oxidation states of vanadium (from +2 as VO to +5 as V2O5) have resulted in various uncontrollable results, a single-step with low annealing temperature synthesis of VO2 (M) remains a challenging issue.
Specially in our work, we focus our attention on the synthesis of VO2 (M) comparing two cost-effective methods: the polyol process  and the hydrothermal one . Our ultimate goal is the synthesis of highly crystallized VO2(M) in a single step.
In the polyol synthesis route, vanadyl ethylene glycolate (VEG) precursor was annealed to prepare VO2 (M) nano powder using various treatments, modifying parameters such as temperature, time and atmosphere. Below 500 °C, X-ray diffraction analysis confirmed the synthesis of highly crystallized VO2(M) with the presence of few impurities such as V6O13 and of an amorphous phase, of which proportion was quantified using the Full-Prof program. For improving the powder’s thermochromic performances, the obtained VO2 (M) was annealed at higher temperature in an inert atmosphere leading as expected to an increase of the quantity of crystallized VO2 (M), and decrease of the amorphous part at the same time while no more impurities were detectable. As shown by Transmission Electron Microscopy whatever the temperature, the particle size of VO2 (M) remained below 50 nm.
In the hydrothermal route, VO2 (B) could be prepared in the microwave oven, and then transformed to VO2 (M) after a further heat treatment. TEM measurements showed that the platelet shape of VO2(B) is maintained for VO2(M) after annealing.
In this presentation, the detailed effectof various conditions in the preparation process and mechanisms of phase transition will be fully investigated and discussed. After the preparation of pure VO2 (M) with highly crystallinity, the influence of doping on the phase transition temperature and hysteresis, will be reported.
. Issam Mjejri, Aline Rougier, and Manuel Gaudon, Low-Cost and Facile Synthesis of the Vanadium Oxides V2O3, VO2, and V2O5 and Their Magnetic, Thermochromic and Electrochromic Properties, Inorg. Chem. 2017, 56, 1734−1741.
. Srinivasa Rao Popuri, Marinela Miclau, Alla Artemenko, Christine Labrugere, Antoine Villesuzanne, and Michael Pollet*. Rapid Hydrothermal Synthesis of VO2 (B) and Its Conversion to Thermochromic VO2 (M1). Inorg. Chem. 2013, 52, 4780-4785.
8:00 PM - ES07.06.08
Multi-Color Electrochromism in RF-Sputtered Vanadium Oxide Thin Films
Gil Joo Song 1 , Aline Rougier 1 Show Abstract
1 , CNRS ICMCB, Pessac France
Vanadium oxide thin films were fabricated by reactive RF magnetron sputtering from two different targets, namely metallic V and V2O5. RF sputtered films deposited in gas mixture of argon and oxygen at room temperature on ITO substrates crystallized in an orthorhombic structure when using a metallic V target while they were amorphous from V2O5 target. Depending on the deposition conditions, the film morphology was layer or needle type. The electrochromic properties of vanadium oxide thin films showed multi steps electrochromism, namely yellow to green, green to blue, and blue to grey, in lithium and sodium based electrolytes. The optical transmittance characterized by UV-visible spectrophotometer showed a maximum difference of 44%, 36% using a metallic V and 30%, 39% using a V2O5 target in Li and Na based electrolytes at 430 nm, respectively. The influence of lithium and sodium insertion/extraction on the structure was investigated using GIXD analysis showing no strong structural change upon cycling. Post-mortem analysis performed after 250 cycles, in particular using scanning electron microscopy, confirmed a better adhesion for amorphous V2O5 thin films (RF sputtered from V2O5 target) cycled in Na based electrolyte as compared to lithium electrolyte. In this presentation, the relationship between the film structure, morphology, thickness, correlated with their deposition conditions and the EC mechanism will be discussed. In conclusion, the EC behaviour of complete devices based on the association of V2O5 and WO3 thin films separated by a lithium based PMMA membrane will be reported.
8:00 PM - ES07.06.09
Optically Tunable, Rewritable Media from Organic Charge-Transfer Liquid Crystalline Films
Joseph Reczek 1 , Bryan Kaehr 2 Show Abstract
1 , Denison University , Granville, Ohio, United States, 2 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Since the development of the first LCD’s almost 50 years ago, liquid crystals have been ubiquitous in media applications as tunable, stimuli-responsive chromogenic materials. Optically rewritable (ORW) liquid crystal alignment is a promising emerging technology with potential advantages in versatility, stability, and cost-efficiency for optical media production. Here, we present a new type of ORW liquid crystal alignment technology based on the tunable laser writing, and rewriting, of novel donor-acceptor columnar liquid crystalline materials (DACLCs). DACLCs are formed from the self-assembly of complimentary electron-rich and electron-poor aromatic components, resulting in alternating mixed-stack columns. These materials exhibit intense charge-transfer (CT) absorbance in the visible-NIR, and are easily processed into ordered thin-films that are strongly dichroic due the directional nature of the CT band. These highly anisotropic films can then be “written” using a moderately powered NIR laser. Due to the strong CT absorption of the film, the laser flash-melts only the irradiated area, and, depending on the speed of writing, either eliminates (fast rate) or completely re-orients (slow rate) film anisotropy in the direction of laser movement. The traverse speed affects the cooling rate; slower movement generates a thermal gradient that redirects film orientation in the vector of dichroic orientation, while fast movement leads to a quick-cooled amorphous state that is isotropic. The films can easily be “erased” and/or rewritten over many cycles. This unique system for ORW can be used to directly write optically active messages and complex patterns for applications in communication and optics, including photomask and e-paper production.
8:00 PM - ES07.06.10
Fabrication and Characterization of Oxygen-Containing Yttrium Hydride Thin Films with Gradient Chemical Composition
Chang Chuan You 1 , Jose Montero 1 , Trygve Mongstad 1 , Erik Marstein 1 , Smagul Karazhanov 1 Show Abstract
1 Department for Solar Energy, Institute for Energy Technology, Kjeller Norway
Oxygen-containing yttrium hydride (YHO) thin films are photochromic under ambient conditions . The optical transmission in such materials can be strongly modulated by exposure to illumination. From a photodarkened state, YHO can be restored to the original highly transparent color state after being stored in darkness for a short time. This switchable optical property is attractive for technological applications such as smart windows and sensors . In this work, we show how reactive magnetron sputtering deposition can be used to prepare YHO thin films with a lateral gradient in oxygen and hydrogen concentrations. This allows us to efficiently study the impact of changes in the chemical composition of the films on their structural, optical and electrical properties. We report a gradual increase in the lattice constant with increasing oxygen content in the film, as revealed by grazing incidence X-ray diffraction measurements. Moreover, the electrical resistivity, measured after 24 h illumination, was found to be ~ 6 orders of magnitude larger in the oxygen-rich photochromic region as compared to the oxygen-poor non-photochromic region in the film. The dependence of the refractive index and the optical density on the varying oxygen content in the film was determined by variable angle spectroscopic ellipsometry.
 T. Mongstad, C. Platzer-Björkman, J.P. Maehlen, L.P.A. Mooij, Y. Pivak, B. Dam, E.S. Marstein, B.C. Hauback, S.Z. Karazhanov, A new thin film photochromic material: Oxygen-containing yttrium hydride, Sol. Energy Mater. Sol. Cells. 95 (2011) 3596–3599.
 K. Yoshimura, C. Langhammer, B. Dam, Metal hydrides for smart window and sensor applications, MRS Bull. 38 (2013) 495–503.
8:00 PM - ES07.06.11
Hydrothermal Synthesis of Monoclinic Phase VO2 Nanowire Array with Highly Ordered
Liang Zhang 1 , Pengcheng Chen 1 Show Abstract
1 Materials Science and Engineering and Shenzhen Key Laboratory of Nanoimprint Technology, South University of Science and Technology, Shenzhen, Guangdong, China
The monoclinic phase vanadium dioxide VO2 (M) has attracted a lot of attention for its special phase transition at a temperature of about 68 degrees. And this transition from an insulator low-temperature phase (M) to a metallic high-temperature phase (R) is followed by amazing changes in electrical and mechanical properties. The synthesis of pure VO2 (M) nanowires via hydrothermal reaction has been reported . Meanwhile, the transition temperature also can be adjusted by doping like tungsten which could further increase the possibility of application achievement. However, the synthesis of VO2 (M) nanowires with high orientation has been considered for a long time. We come up with a new method to fabricate pure VO2 (M) nanowires (in 10 μm lengths, 100nm diameters) vertically with highly ordered on the rough surface of quartz via hydrothermal reaction. Obviously, this achievement enlarges and perfect its intrinsic application. For instant, we could assemble an actuator with large scale as long as we can get our nanowires longer in further research.
 D. Alie, L. Gedvilas, Z.W Wang, R. Tenent, C. Engtrakul, Y.F Yan, S.E. Shaheen, A.C. Dillon, C.M Ban. Direct synthesis of thermochromic VO2 through hydrothermal reaction. Journal of Solid State Chemistry 212 (2014) 237–241.
 Y.F. Zhang, J.C. Zhang, X.Z. Zhang, Y. Deng, Y.L. Zhong, C. Huang, X. Liu, X.H. Liu, S.B. Mo. Influence of different additives on the synthesis of VO 2 polymorphs. Ceramics International 39 (2013) 8363–8376.
Aline Rougier, Institut de Chimie de la Matière Condensée de Bordeaux
Smagul Karazhanov, Institute for Energy Technology (IFE)
John Reynolds, Georgia Institute of Technology
Kazuki Yoshimura, Advanced Industrial Science and Technology (AIST)
Wednesday AM, November 29, 2017
Hynes, Level 3, Room 301
8:30 AM - *ES07.07.01
Photochromism in Yttrium and Rare Earth Based Oxyhydrides
Bernard Dam 1 , Fahimeh Nafezarefi 1 , Herman Schreuders 1 , Steffen Cornelius 1 Show Abstract
1 , TU Delft, Delft Netherlands
Photochromism in yttrium oxyhydride has the benefit that it does not depend on UV excitation. This is a promising feature for the use of this material at the inner glass surface of a double glazed window pane. Such pane would automatically darken on irradiation by sunlight. For such an application a sizeable change (e.g. >50%) in optical transmission is required. In addition, the speed of switching should be fast enough (minute scale). In YHx it was shown that such a transition can be induced by optically creating charge carriers, which are long-lived at temperatures below 200 K. Oxyhydride films show a similar behaviour with a concurrent photodarkening at room temperature. These films are reactively sputtered dihydride films, which oxidize on exposure to air. The oxidation is self-limiting and - depending on the nature of the as-deposited films - results in a bandgap of about 2.6 eV. Typical photodarkening time constants are around 10 min while the photo-darkening contrast saturates at values around 45% at a film thickness of around 1 micron. Bleaching is much slower, showing typical time constants above 100 min. Bleaching times are considerably shortened by long-wavelength illumination. The largest contrast change is observed between 400 and 900 nm and therefore nicely covers the visual wavelength range.
The mechanism for this photochromic effect is still debated. Two lines of reasoning are being explored. The first one considers a band gap excitation followed by the capture of the excited carrier by a defect. Assuming multiple defect levels, the absorption of light will be due to excitations within these levels. The second model assumes again a bandgap excitation which is followed by clustering of point defects and formation of nanoparticles, in much the same way as in the classical, photochromic AgCl based glasses. The latter mechanism seems most likely, since the slow point defect mobility involved would explain the relatively slow kinetics of the photochromic effect.
To enhance the point defect mobility we investigated the photochromic behaviour in some rare earth oxyhydrides. We found that the rare earth oxyhydrides investigated so far (Er, Dy, Gd) showed photochromic behaviour. The optical bandgap in these materials tends to be smaller as compared to Y. However, no systematic dependency of the switching speed in relation to the lattice constant was found. All rare earths showed signatures of a large amount of in-bandgap states. Remarkably, the Gd based samples showed the largest photochromic optical contrast observed so far. Additionally, the contrast extends over a much larger wavelength range which is advantageous in terms of heat management when used in double glazed window panes. While the reason for these differences have yet to be discovered our findings show that further exploration of the different oxyhydride materials may be used to further optimize their photochromic properties.
9:00 AM - ES07.07.02
The Photochromic Effect in Rare-Earth Oxy-Hydride Thin Films
Steffen Cornelius 1 , Fahimeh Nafezarefi 1 , Bernard Dam 1 Show Abstract
1 , Delft University of Technology, Delft Netherlands
Inorganic photochromic materials (PCM) are promising for applications such as energy saving smart windows, because of their higher stability vs. oxygen, moisture and elevated temperatures in comparison to organic PCMs. However, only a few inorganic photochromic materials are known so far. With the exemption of photochromic silver halide dopes glasses, the photochromic mechanisms and performance limits of inorganic PCMs are generally not very well understood. Recently, an interesting photochromic effect was discovered in oxygen containing yttrium hydride (YOH) thin films. This is a transparent semiconductor with a bandgap of about 2.6 eV. The photo-darkening of YOH is triggered by UV light, occurs in a wide spectral range and is nearly colour-neutral - giving darkened films a greyish appearance. The photochromic effect is reversible at room temperature (in the dark) and bleaching is accelerated by illumination with long wavelength light.
Currently, the nature of the photochromic mechanism in YOH is under debate. Moreover, photochromic parameters like maximum optical contrast and speed of darkening and bleaching are of high relevance for practical applications. Therefore, we set out to search for more materials that show YOH-like photochromism and to investigate systematically their photochromic properties.
We discovered that also the rare earth metal oxy-hydrides, in particular Gd, Dy and Er are photochromic. This enables us to study structural and chemical effects of the cation on the photochromism in this material group. The observed similarities in photo-darkening and bleaching with respect to YOH indicate that the photochromic effect is governed by the same physical mechanism. On the other hand, we find that the optical band gap, photochromic contrast and wavelength range of photochromic response depend on the type of cation. Remarkably, GdOH thin films show the strongest photochromic contrast (up to 45% transmittance variation at only 300nm film thickness) in a very wide spectral range. These results suggest that cation alloying is an interesting approach to tailor the photochromic properties of oxy-hydrides for specific applications. Additionally, further exploration of the photochromic properties of rare-earth oxy-hydrides might lead to a better understanding of the photochromic mechanism in this group of materials.
9:15 AM - ES07.07.03
Flux Dependence of Photochromic Effect in Oxygen-Containing Yttrium Hydride
Tang Ye 1 , Jose Montero 2 , Yong Zhang 1 3 , Smagul Karazhanov 2 Show Abstract
1 Nanoscale Science Program, University of North Carolina at Charlotte, Charlotte, North Carolina, United States, 2 Department for Solar Energy, Institute for Energy Technology, Kjeller Norway, 3 Department of Electrical and Computer Engineering, University of North Carolina at Charlotte, Charlotte, North Carolina, United States
Oxygen-containing Yttrium Hydride (YHO) is a new type of photochromic material . YHO thin films have been deposited by magnetron sputtering at different hydrogen/argon pressures in in a Leybold Optics A550V7 sputter unit. Reversible color change has been observed in YHO films prepared under different conditions with the illumination of a focused 442 nm laser (illumination beam) and probed by non-focused white light (probe beam). The measurements were carried out on a Horiba LabRam HR800 Raman microscope using a 50x microscope lens with NA = 0.5. After the illumination beam is turned on, visually the illuminated region changes its color from yellowish transparent to a darkened black-like color within a few minutes, depending on the illumination density. The color change can be reversed after shutting off the illumination beam. On the other hand, the color change is not observed under 532 nm illuminations at comparable power density.
Time-resolved reflectance of the material, monitored in the visible spectral range near 535 nm, shows an exponential decay of the reflectance while the material is under continued illumination of the focused 442 nm beam. Comparing the reflectance changes at different power densities, varied in 5 orders in magnitude from approximately 4.4 W cm-2 (D4) to 4.4 x 105 W cm-2 (D0), one sees faster decay at higher power density, i.e., the time necessary to reach a certain level of reflectance change is shorter if provided with a higher power density. Quantitatively, to reach 10% reduction in reflectance for one particular sample, the D3 power density needs ~1280 sec, while the D2 needs ~110 sec, and the D1 only needs ~10 sec. However, to reach the maximum possible reduction about 50%, ~1000 sec is required under D0. The results indicate that the reflectance drop depends mostly only on the photon flux, multiplication of power density and illumination time. Although the maximum reduction in reflectance varies from sample to sample, the flux dependence is found to be universal in all the samples that have been studied. This finding provides an important hint on the mechanism of the photochromic effect. Since it has been proposed that the change in the state of oxygen atoms in the film is responsible for the photochromic effect , we speculate that the constant number of photons are required to interact with certain number of oxygen atoms in order to yield the same amount of the optical property change, and the variation from sample to sample reflects the variation in the amount of oxygen. Further correlative property – elementary analysis investigation will be carried out to understand the underlying mechanism of the finding.
 T. Mongstad et al. Solar Energy Materials and Solar Cells 95, 3596 (2011).
 C. C. You, et al. Appl. Phys. Lett. 105, 031910 (2014).
9:30 AM - ES07.07.04
The Connection Between Photochromic Properties and Chemical Composition of Oxygen-Containing Yttrium Hydride Thin Films
Dmitrii Moldarev 1 2 3 , Daniel Primetzhofer 2 , Chang Chuan You 3 , Smagul Karazhanov 3 , Jose Montero 3 , Fredrik Martinsen 3 , Trygve Mongstad 3 , Erik Marstein 3 , Max Wolff 2 Show Abstract
1 Department of Materials Science, NRNU MEPhI, Moscow Russian Federation, 2 Department of Physics and Astronomy, Uppsala University, Uppsala Sweden, 3 Department for Solar Energy, Institute for Energy Technology, Kjeller Norway
Oxygen-containing yttrium hydride is a promising photochromic material for application in smart windows and sensors as it exhibits reversible coloring at ambient conditions. In the previous works, it was established that the photochromic response (the change in optical transmittance between the bleached state and the photodarkened state) strongly depends on the deposition. In the current work, we focus on a detailed investigation of the chemical composition by ion-beams techniques. We establish the correlation between the composition of the film and the optical and electrical properties. Our results are consistent with oxygen-containing gadolinium hydride films reported earlier. In addition, repeated measurements of the uncapped films reveal a gradual oxidation upon exposure to air and a degradation of the photochromic properties. This result demonstrates the necessity coatings to encapsulate the layer. Finally, by investigation of films with a lateral gradient of oxygen and hydrogen concentration, we observe a transition from a non-photochromic state to a photochromic behavior induced by a continuous oxidation process. We report the photochromism being most pronounced in the transformed region. These findings demonstrate the possibility of producing films with tunable photochromic properties by changing the chemical composition of the oxygen-containing yttrium hydride.
10:30 AM - *ES07.07.06
Switchable Mirrors Using Mg-Y Alloys for Smart Windows
Yasusei Yamada 1 , Kazuki Yoshimura 1 Show Abstract
1 , AIST, Nagoya Japan
“Switchable mirrors” can change their optical properties reversibly between reflective and transparent states owing to hydrogenation and dehydrogenation. The mirror is composed of two thin metallic layers, which are switchable Mg or rear-earth alloy and catalytic Pd layers with their thickness of ~50 nm and ~5 nm, respectively. These layers are deposited by direct current magnetron sputtering on a transparent substrate, such as glasses and plastics. As deposited film shows a shiny metallic appearance, that is reflective state, and when the mirror is exposed to hydrogen containing gas, the optical property changes to transparent state owing to reaction of alloy layer with hydrogen to form the hydride in the atmosphere through the effect of Pd catalysis. When the hydrogenated transparent mirror is exposed to the air, the hydrogen in the mirror reacts with oxygen in the air and removes from the mirror as water vapor. As a result, the optical property returns to metallic state.
The mirrors can change the optical transmittance by changing the optical reflectance. Therefore, when they use as the switchable glazing in smart windows, they can control the solar irradiation getting into rooms through windows, leading to saving energy for air-conditioning. The mirrors are required the following properties for the application to window glazings: high visible transmittance and high achromatic property in the transparent state, large modulation in the region of solar radiation and high switching durability between the reflective and transparent states.
We have developed a switchable mirror using Mg-Y alloy to satisfy the above all requests. The developed mirror has high switching durability of over 10,000 cycles and the mirror coated with antireflective layer on the Pd layer has high visible transmittance of ~70% in the transparent state and large modulation of ~60% and ~50% on the visible and near infrared region, respectively.
We have focused on “gasochromic” instead of electrochromic from the following viewpoints. 1) cost: 1-a) no transparent conducting electrodes, such as ITO, 1-b) high manufactured throughput due to very thin metallic layer and high sputtering yield of metal targets, 1-c) no mask fabrication due to no terminals. 2) large modulation: 2-a) no transparent conducting electrodes, which reflect near infrared, 2-b) transform between metal and insulator.
Thus, we believe that switchable mirrors using gasochromic phenomenon are one of the most promising materials for smart window applications.
In this presentation, we will also show the gasochromic switching system for practical use.
11:00 AM - ES07.07.07
Oxygen-Containing Yttrium Hydride as a Photochromic Material
Jose Montero 1 , Chang Chuan You 1 , Smagul Karazhanov 1 , Erik Marstein 1 Show Abstract
1 , Institute for Energy Technology (IFE), Kjeller Norway
Oxygen-containing yttrium hydride (YHO) is a wide band semiconductor which exhibits photochromic behaviour: transparent YHO thin films reversibly switch from a transparent state to a photodarkened state after being illuminated with UV or blue light. This photochromic behaviour in YHO was observed for the first time by T. Mongstad et al. in 2011, and since then YHO was included in the family of the inorganic and photochromic materials. Due to its novelty, and despite its multitude of potential technological applications -which include smart fenestration, ophthalmic lenses, agricultural films, security markings and many more- very little is known about YHO. The present work is intended to shed some light on the physical properties of YHO thin films keeping in mind the possible technological applications. This includes exploring practical aspects such as the band gap of the thin films and band gap engineering, the luminous transmittance modulation and the study of the electrical properties (in the clear and photodarkened state). Other aspects, such as the influence of the deposition conditions on the aforementioned physical properties, the influence of the substrate on the growth and crystalline structure of the films and the physical origin of the photochromic effect, will also be discussed.
T. Mongstad, C. Platzer-Björkman, J.P. Mæhlen, L.P.A. Mooij, Y. Pivak, B. Dam, E.S. Marstein, B.C. Hauback, S.Zh. Karazhanov, A new thin film photochromic material: Oxygen-containing yttrium hydride, Sol. Energy Mater. Sol. Cells. 95 (2011) 3596–3599.
J. Montero, F. A. Martinsen, M. García-Tecedor, S. Zh. Karazhanov, D. Maestre, B. Hauback, and E. S. Marstein, Photochromic mechanism in oxygen-containing yttrium hydride thin films: An optical perspective. Phys. Rev. B 95, 201301(R).
J. Montero, F. A. Martinsen, M. Lelis, S. Zh. Karazhanov, B. C. Hauback, E. S. Marstein, Preparation of yttrium hydride-based photochromic films by reactive magnetron sputtering, Sol. Energy Mater. Sol. Cells, in press. https://doi.org/10.1016/j.solmat.2017.02.001.
11:15 AM - ES07.07.08
Comparing the Optical Properties of Ordered and Disordered Perylene Dyes inside the Silica Nanoparticles
Suresh Valiyaveettil 1 , Deepa Sriramulu 1 , Prashant Turaga 2 , Andrew Bettiol 2 Show Abstract
1 Department of Chemistry, National University of Singapore, Singapore Singapore, 2 Department of Physics, National Unviersty of Singapore, Singapore Singapore
Optically active silica nanoparticles are interesting owing to high stability and easy accessibility. Unlike previous reports on dye loaded silica particles, here we investigate the correlation between the molecular arrangement of perylenes with changes in optical properties of silica nanoparticles. Three differentially functionalized fluorescent perylene - silica hybrid nanoparticles were prepared from appropriate ratios of perylene derivatives and tetraethyl orthosilicate (TEOS) and investigated the structure property correlation. The particles differ from each other on the distribution, organization and intermolecular interaction of perylene inside or outside the silica matrix. Structure and morphology of all hybrid nanoparticles were characterized using a range of techniques such as electron microscope, optical spectroscopic measurements and thermal analysis. The organizations of perylene in three different silica nanoparticles were explored using steady-state fluorescence, fluorescence anisotropy, lifetime measurements and solid state polarized spectroscopic studies. The interactions and changes in optical properties of the silica nanoparticles in presence of different amines were tested and quantified both in solution and in vapor phase using fluorescence quenching studies.
11:30 AM - *ES07.07.09
Photochromic Diarylethenes for Light-Triggered Optical Elements and Optoelectronic Devices
Chiara Bertarelli 1 Show Abstract
1 , Politecnico di Milano, Milan Italy
Materials which reversibly modify their physical and chemical properties upon light exposure have found in photochromic switches promising candidates. The colour change in photochromic systems is the eye-sighted consequence of a molecular isomerization, and it has been successfully applied in transition sunglasses and inks.
In 1,2-diarylethenes, both the coloration and bleaching processes are controlled by light. We show that this thermally irreversible photochromism can open to active optics, and metrology of aspheric and free-form optical lenses and mirrors.1,2 Examples focus on focal plane masks for astronomical instrumentation, amplitude holograms and masks for optical nanolithography. To demonstrate working devices, photochromic switches have been designed and materials engineered to meet the requirements of i) film flatness, homogeneity and low scattering, ii) intense and fast response and iii) thermal and shape stability. We also developed a kinetic model, which allows for a control over the writing process of the optical devices.3
Moreover, the light-trigger isomerization can be accompanied by non negligible modifications of polarizability, dipole moment, refractive index, conductivity, luminescence, wettability, etc. In this framework, some cases have been faced by our group to develop new concept devices.4,5
For any application device lifetime has to be considered, and a new insight to understand the fatigue resistance of photochromic diarylethenes is shown.6
1. C. Bertarelli et al., J. Photochem. Photobiol. C, Photochem. Rev. 2011, 12, 106.
2. R. Alata et al., Optics Express, 2017, 25, 6945.
3. G. Pariani et al. Opt. Lett., 2013, 38, 3024.
4. A. Bianco et al. Phys. Chem. Chem. Phys., 2016, 18, 31154.
5. R. Castagna et al. J. Phys Chem. Lett., 2012, 3, 51.
6. G. Pariani et al., J. Phys Chem. C, submitted.
ES07.08: Electrochromic III
Wednesday PM, November 29, 2017
Hynes, Level 3, Room 301
1:30 PM - *ES07.08.01
LSPR Band Tunable Ag Electrodeposition Based Electrochromic Cell Enabling Multicolor Representation
Norihisa Kobayashi 1 Show Abstract
1 , Chiba University, Chiba Japan
Electrochromism (EC) is defined as a reversible color change by electrochemical redox reaction and has several features such as color variation, memory property and so on. Multifunctional electrochromic materials which control multiple colors, various color density, and specular reflection are expected to be potential candidate for energy-saving light-modulation device such as smart window and novel reflective display device such as e-paper.
We reported silver (Ag) deposition–based EC device achieving three optical states-transparent, silver-mirror, and black-in a single cell1). Its underlying mechanism was based on the electrodeposition of Ag nanoparticles on two facing transparent electrodes, a flat indium thin oxide (ITO) electrode and an ITO particle modified electrode. The EC material, gel electrolyte containing Ag+ ion, was sandwiched by the two electrodes. The device’s default state was transparent, whereas, applying a negative voltage to one or the other electrode causes the electrodeposition of Ag on its surface. When Ag was deposited on the flat ITO electrode, the device turns mirror. On the other hand, when Ag was deposited on the rough ITO particle modified electrode, the device turns black.
Electrodeposition is also an attractive method to create colors because Ag nanoparticles exhibit various optical states based on their localized surface plasmon resonance (LSPR). LSPR bands of Ag nanoparticles are affected by the size and shape2). The control of LSPR, therefore, must enable dramatic changes in color for the surface where nanoparticles are deposited. We successfully demonstrate the first LSPR based multicolor EC device enabling reversible control of six optical states such as transparent, silver mirror, cyan, magenta, yellow and black, which is attractive for smart window as well as color e-paper application3,4). We will discuss the mechanism of electrodeposition and a wide range of its applications.
1) S. Araki, K. Nakamura, K. Kobayashi, A. Tsuboi and N. Kobayashi, Adv. Mater. 2012, 24, OP122.
2) T. Huang and X. H. Nancy Xu, J. Mater. Chem. 2010, 20, 9867.
3) A. Tsuboi, K. Nakamura and N. Kobayashi, Adv. Mater. 2013, 25, 3197.
4) A. Tsuboi, K. Nakamura and N. Kobayashi, Chem. Mater., 2014, 26, 6477.
2:00 PM - ES07.08.02
A Novel AIEgen-Based Mechanochromic Multi-Color Switching Material
Changqing Chen 1 , Xiao Meng 2 , Xue Li 2 , Yuguo Ma 2 Show Abstract
1 Department of Chemistry and Physics, Salem State University, Salem, Massachusetts, United States, 2 Beijing National Laboratory for Molecular Sciences, Center for Soft Matter Science and Engineering, Key Lab of Polymer Chemistry & Physics of Ministry of Education, College of Chemistry, Peking University, Beijing China
A novel multi-color switching mechanochromic AIEgen material was synthesized and characterized. The fluorescence of this material nearly covers the entire visible spectrum under different pressures. The molecule was designed to attach spiropyran (SP) moiety on tetraphenylethylene (TPE). The covalent bonding attachment of SP to TPE is crucial, which enables the tuning of the fluorescence from no color change, two-color switch to three-color switch under grinding due to the amorphization of TPE moiety and the isomerization of spiropyran moiety. Under quantifiable hydrostatic pressures, multi-color switching with a wide spectral response region was achieved, resulting from distinct pressure thresholds for supramolecular and chemical structural changes. The attached spiropyran moiety helped to enhance the response of the mechanochromic AIEgen to show more remarkable color changes. The development of this molecule showcases a successful strategy of utilizing the molecular design to tune the mechanochromic responses of a material triggered by grinding or high pressures. The multi-color changes, excellent responses in a wider visible region and the enhanced fluorescence intensity offer this molecule great potentials for applications in areas such as visual pressure sensors, pressure calibration, mechanoprobes, security inks, etc.
2:15 PM - ES07.08.03
Robust Dynamic Windows Based on the Reversible Electrodeposition of Bi and Cu
Tyler Hernandez 1 , Christopher Barile 3 2 , Michael Strand 3 , Daniel Slotcavage 3 , Michael McGehee 3 Show Abstract
1 Chemistry, Stanford University, Menlo Park, California, United States, 3 Materials Science and Engineering, Stanford University, Stanford, California, United States, 2 Chemistry, University of Nevada, Reno, Reno, Nevada, United States
Optoelectronically tunable dynamic windows based on reversible metal electrodeposition are exciting alternatives to static lighting controls such as blinds and shades. We study the electrodeposition and stripping of Bi and Cu on transparent conducting electrodes modified with Pt nanoparticles for use in dynamic windows. Spectroelectrochemical measurements combined with scanning electrode microscopy (SEM) images indicate that the ratio of Bi to Cu in the electrolyte drastically affects electrode switching speed and electrodeposit morphology. From these results, we propose a mechanism that accounts for the chemical and electrochemical reactions that occur during metal electrodeposition and stripping in Bi-Cu electrolytes. These findings allow us to construct dynamic windows on a 25 cm2 scale that possess reversibly tunable transmission between transparent and color neutral opaque states. Specifically, these devices exhibit a >60% contrast ratio after 30 s of metal electrodeposition and return to their transparent state within <5 s. This rapid cycling can be maintained over the course of at least 1,000 cycles without any degradation of contrast ratio or uniformity. Finally, the Bi-Cu windows do not consume power to maintain either their transparent or opaque states. Their combination of fast switching kinetics, durable cycle lives, and excellent resting stability make dynamic windows based on Bi-Cu reversible electrodeposition promising candidates for next generation energy-efficient dynamic windows.
3:30 PM - ES07.08.04
Norbornadiene Derivatives for Molecular Solar Thermal Applications
Anne Petersen 1 , Martyn Jevric 1 , Mads Mansø 1 , Zhihang Wang 1 , Ambra Dreos 1 , Kasper Moth-Poulsen 1 Show Abstract
1 , Chalmers University of Technology, Gothenburg Sweden
Energy consumption has been steadily rising, yet on the other hand, the need for cleaner and sustainable sources is necessary to minimalize global impact. Nature provides us many alternatives, such as wind, water and sunlight and much work has gone into harnessing these resources towards cleaner generation of electricity. Less scientific progress has been made into storing this energy, which is also an important aspect as the sun does not shine continuously and one cannot count on wind in the weather forecast every day. Molecular Solar Thermal storage (MOST) is a technology that utilizes the sun’s energy to convert a chromophoric molecular to its high energy isomer .1 The concept involves that the energy is stored in a metastable photoisomer until required, where it can be released upon the application of a stimulus. In this context, one of the more promising molecular candidates are norbornadiene (NBD) derivatives, which can form quadricyclane (QC) upon irradiation. The stored energy can be released as heat by promoting the reverse reaction to NBD by use of a catalyst.2 One key challenge of this system is the absorbance overlap of the norbornadiene derivative with the solar spectrum. We have previously shown that the onset of absorbance for these simple organic molecules can be can be red shifted to as high as 462 nm, by employing a donor/acceptor system combination over one of the double bonds of the NBD.3 Another desirable quality for MOST is a high energy density, where low molecular weight materials are important. NBD, itself, is small motif but the addition of donor/acceptor units moderately increase the molecular weight, where an enthalpic release as high as 396 kJ/kg has been achieved.4 Moreover, hybrid energy storage devices has been fabricated converting up to 1.1% of the incoming sunlight into stored chemical energy and at the same time 80% of incoming light in heated water.2a Here we present the synthesis and characterization of a new array of donor/acceptor containing NBDs, where the molecular weight has intentionally been kept low in order to identify the best possible molecules with even higher energy densities and improved solar spectrum match for future MOST applications.
1 a) Lennartson, A., Roffey, A., Moth-Poulsen, K., Tet. Lett. 2015, 56, 1457. b) Moth-Poulsen, K., Coso, D., Börjesson, K., Vinokurov, N., Meier, S. K., Majumdar, A., Vollhardt, K. P. C., Segalman, R. A. Energy Environ. Sci. 2012, 5, 8534. 2 a) Dreos, A., Börjesson, K., Wang, Z., Roffey, A., Norwood, Z., Kushnir, D., Moth-Poulsen, K. Energy Environ. Sci. 2017, 10, 728. b) Miki, S., Asako, Y., Morimoto, M., Ohno, T., Yoshida, Z., Maruyama, T., Fukuoka, M., Takada, T., Bull. Chem. Soc. Jpn. 1988, 61, 973. 3 Gray, V., Lennartson, A., Ratanalert, P., Börjesson, K., Moth-Poulsen, K. Chem. Commun. 2014, 50, 5330. 4 Quant, M., Lennartson, A. Dreos, A. Kuisma, M. Erhart, P. Börjesson, K. Moth-Poulsen, K. Chem. Eur. J. 2016, 22, 13265.
3:45 PM - *ES07.08.05
The Use of Organometallic Complexes to Squeeze Every Last Photon out of Organic LEDs
Mark Thompson 1 , Patrick Saris 1 , Rasha Hamze 1 , Shuyang Shi 1 , Peter Djurovich 1 Show Abstract
1 , University of Southern California, Los Angeles, California, United States
We have developed a great deal of chemistry around phosphorescent Iridium and Platinum complexes for monochromatic and white OLEDs. These materials give LEDs with efficiencies nearing the theoretical limits. In this talk will discuss the evolution of organometallic emitters for OLEDs, highlighting our results with Iridium and platinum based materials, with particular emphasis on materials for blue phosphorescent OLEDs. The issues with blue electrophosphorescence center on both color purity and device lifetime, both of which wil be discussed. Time permitting I will discuss our recent work with Copper based phosphors for electroluminescence. Copper based materials offer the possibility of using lower cost materials, but are typically less stable than their Ir counterparts and have longer excited state lifetimes.
4:15 PM - ES07.08.06
A Complementary Electrochromic Device Composed of Co(II)-Based Metallo-Supramolecular Polymer, Prussian Blue and Ferrocene
Li-Yin Hsiao 1 , Hsin-Che Lu 1 , Sheng-Yuan Kao 1 , Ting-Hsiang Chang 1 , Yen-Chun Wang 1 , Kuo-Chuan Ho 1 2 Show Abstract
1 Department of Chemical Engineering, National Taiwan University, Taipei Taiwan, 2 Institute of Polymer Science and Engineering, National Taiwan University, Taipei Taiwan
Among all electrochromic materials, Co(II)-based metallo-supramolecular polymer (PolyCo) draws much attention for its black-to-transmissive color changing feature, which provides a panchromatic hue upon coloring and therefore could serve as a potential candidate for electrochromic display. Despite of its appealing advantages including dramatic color change, fast response, and outstanding stability, PolyCo is rarely applied in the field of electrochromic device (ECD). In order to fabricate a high-contrast complementary ECD with good stability, we proposed an ECD composed of a cathodically coloring thin film (PolyCo), an anodically coloring thin film (Prussian blue, PB), and a redox mediator (ferrocene, Fc). The addition of Fc in the proposed ECD could accelerate electron transfer so as to shorten the response time and enhance the cycling stability. The PolyCo/Fc/PB ECD exhibits a reversible transmittance change of 60.5% at 690 nm when switched between 1.2 V and -1.9 V. During potential switching, the fabricated ECD exhibits the unique multi-color characteristic, which shows four different colored states at 1.2, 0.2, -0.6, and -1.9 V, respectively. In addition, the device (active area = 2.0 cm x 2.0 cm) shows fast bleaching and coloring response times of 1.5 and 0.9 s, respectively. Moreover, the proposed PolyCo/Fc/PB ECD reveals good long-term stability with a 96.9% retention of its original transmittance change after 2,500 cycles.
4:30 PM - ES07.08.07
Cobalt Hexacyanoferrate Nanoparticles for Wet-Processed Brown–Bleached Electrochromic Devices with Hybridization of High-Spin/Low-Spin Phases
Kazuki Tajima 1 , Elghool Kholoud 2 1 , Hiroshi Watanabe 1 , Akira Takahashi 1 , Mahmoud Emara 2 , Bashir A. Abd-El-Nabey 2 , Masato Kurihara 3 1 , Tohru Kawamoto 1 Show Abstract
1 , AIST, Tsukuba Japan, 2 , Alexandria University, Alexandria Egypt, 3 , Yamagata University, Yamagata Japan
To prepare electrically colour-switching brown and bleached devices, we investigated the electrochromism of electrodes with cobalt hexacyanoferrate (CoHCF) fabricated by the coating of ink composed of water-dispersible CoHCF nanoparticles (CoHCF-NP). The CoHCF-NP with surface modification by hexacyanoferrate anion was well dispersed into aqueous solution. A film shows clear brown or bleached colour change by applied potential switching between + 1.4 V and -0.4 V. To exhibit the brown colour during electrochromism, the co-existence of the Co(III)-Fe(II) blue low spin and the Co(II)-Fe(III) red high spin state are expected to be crucially important. Hybridization of the spin states was confirmed by the shift of the infrared spectrum corresponding to the CN-vibration mode. CoHCF-NP implemented electrochromic devices exhibiting the brown–bleached colour change were also demonstrated in a combination with a counter-electrode of zinc hexacyanoferrate nanoparticles having no colour in either redox state.