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Materials and light


Chromogenic Materials and Devices

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This symposium provides a forum for discussion and presentation of fundamental and applied aspects of chromogenic materials (photochromism, gasochromism, electrochromism, thermochromism, and other chromisms) and their device applications, such as windows, displays. Novel materials, devices design, and modeling will receive specific attention. 



Chromogenic materials are able to change their optical properties in response to an external stimulus such as temperature (thermochromism), light (photochromism), electrical charge insertion (electrochromism), gas pressure and composition (gasochromism). Chromogenic materials are currently present in more and more products. Nowadays, self darkening electrochromic rear view mirrors operate on millions of cars, back in 2005 car roof electrochromic windows were installed on the Ferrari SuperAmerica, photochromic sunglasses are commonly used. Other applications are also related to the infrared region including thermal control for satellite or IR camouflage. In this symposium, particular attention will concern the architectural glazing and the various means to save energy using chromogenic coatings. Chromogenic materials concern numerous chemical systems, from organic to inorganic or even hybrids. In addition to continuing interest in traditional chromogenics materials particular attention will concern novel materials including doping systems, and original synthesis routes.  Specific attention will be devoted to device design including interfaces issues, and optimization of critical parameters such as durability, stability, switching time. Transparent electric and ionic conductors will be strongly covered. Strong emphasize will be directed towards modeling and theoretical work.


Hot topics to be covered by the symposium:

  • Electrochromic Materials and  Devices
  • Thermochromic Materials and Devices
  • Gasochromic Materials and Devices
  • Photochromic Materials and Devices
  • Other Chromic Materials and Devices
  • Transparent electric and ionic conductors
  • Inorganic, organic, hybrid Materials and Devices
  • Energy saving in building
  • Modeling and theory
  • Mechanisms of chromogenic materials

The proposed topics include, but will not be limited to:

  • Novel Materials for Chromogenics Applications
  • New Synthesis and Fabrication Methods
  • Thin Film Techniques for preparation of chromogenic devices (Sputtering, Sol-gel, Pulsed Laser Deposition, Electrodeposition....)
  • Combinatorial approach in search and optimization of chromogenic materials
  • Application of chemochromic devices



The proceedings will be published in Solar Energy Materials and Solar Cells.


Symposium organizers:


Aline Rougier
Institut de Chimie de la Matière Condensée de Bordeaux
87 av. Du Dr. Schweitzer
33600 Pessac
Phone: +33 5 40 00 62 63
Fax : +33 5 40 00 27 93


Claes G. Granqvist
Dept. of Engineering Sciences
The Angstrom Laboratory
Uppsala University
P.O. Box 534
SE-75121 Uppsala
Phone: +46 (0)18 4713067
Fax: +46 (0)18 4713270


Bernard Dam
Chemical Engineering, Faculty of Applied Sciences Address
Delft University of Technology
Building B12, Room 1.209
Julianalaan 136
NL-2628 BL Delft PO Box 5045
NL-2600 GA Delft
The Netherlands
Phone: +31152784342
Fax: +31152787412


Martyn Pemble
Tyndall National Institute and Department of Chemistry
University College Cork
Phone: +353 (0)21 490 4456
Fax: +353 (0)21 427 0271

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Authors : Shuyi Li, Gunnar A. Niklasson, Claes G. Granqvist
Affiliations : Department of Engineering Sciences, Solid State Physics, The Ångström Laboratory, Uppsala University, Uppsala, Sweden

Resume : Thermochromic VO2 is a promising material for energy-efficient window applications. It goes through a metal-to-insulator transition at a critical temperature Tc of ~68 °C. This phenomenon also enables transmittance modulation in the solar infrared region and lays a foundation for thermochromic VO2-based energy-efficient fenestration. Historically, high Tc, low luminous transmittance and low solar transmittance modulation have been the three challenges to the performance of VO2-based materials. Doping has been reported to offer a number of solutions: W-doping can reduce Tc effectively, and Mg-doping can reduce Tc and improve luminous transmittance. Furthermore, VO2 nanoparticle composites were found to offer so called nanothermochromic properties, which enable dramatic improvements in luminous transmittance and solar transmittance modulation simultaneously. The study to be presented is focused on undoped and Mg-doped VO2 films and nanoparticle composites. Optical constants were obtained for experimentally prepared VO2 films with Mg contents 0 < Mg/(Mg + V) < 0.21. Luminous transmittance and solar transmittance for films and nanoparticle composites were calculated for varied thickness and Mg-contents. The performance limits of undoped and Mg-doped VO2 films and nanoparticle composites were shown as a relation between luminous transmittance and solar transmittance modulation. Mg-doping was found to improve the optical performance of films but to impair that of the nanoparticle composites. A generally preferable degree of Mg-doping was found to be Mg/(Mg + V) < 0.06. The positive effect of antireflection treatment on Mg-doped VO2 films is discussed too.

Authors : C. Vinod Chandran(a), Herman Schreuders(b), Bernard Dam(b), Jakob Bart(a), J. W. G. Janssen(a), P. J. M. van Bentum(a), Arno P. M. Kentgens(a)
Affiliations : (a) Solid-state NMR, Institute for Molecules and Materials, Nijmegen, The Netherlands (b) Chemical Engineering, Delft University of technology, Delft, The Netherlands

Resume : The photochromic effect of oxygen doped yttrium hydride (YHxOy) thin films is studied by solid-state NMR. The photochromic effect causes changes in optical and conduction properties of the YHxOy film when irradiated with light. We have used the novel NMR strip-line probe technology to investigate this effect. In comparison with pure yttrium hydride (YHx) thin films, the 1H NMR study showed reversible changes for YHxOy before and after light irradiation. Mobility of some hydrogen species was found to be diminishing during the photochromic darkening. The high sensitivity of the strip-line NMR probe helped to observe these changes. With the help of 89Y{1H} Cross-polarization MAS experiment we found some of the yttrium species getting to a metallic state during the darkening process. The 89Y-1H 2D correlation spectrum shows a close proximity of those yttrium atoms with the hydrogen species near the oxygen atoms. Therefore, the static NMR experiments help to observe the dynamics of the system whereas the MAS NMR experiments show the chemical and structural information. With the help of observed NMR data the present work suggests a model for the structural transformation during the reversible photochromic changes in YHxOy thin-films, as a result of illumination.

Authors : Rémi Dessapt (a), Khadija Hakouk (a), Stéphane Jobic (a), Anne Dolbecq (b), Olivier Oms (b), Pierre Mialane (b)
Affiliations : (a) Institut des Matériaux Jean ROUXEL, Université de Nantes, CNRS, 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3, France (b) Institut Lavoisier de Versailles, UMR 8180, Université de Versailles Saint-Quentin en Yvelines, 45 Avenue des Etats-Unis, 78035 Versailles cedex, France

Resume : The combination of inorganic polyoxometalates (POMs) with photoswitchable organic molecules such as spiropyrans (SP) and spironaphthoxazines (SN) has recently opened up the way to new hybrid materials with highly tunable solid-state photochromic and electrochromic properties in ambient conditions. Two complementary strategies have been successfully conceived. The first approach consists in assembling POMs with a cationic spiropyran into supramolecular networks [1]. The nature of the POM units and the design of the frameworks impact both the initial color of these charge-transfer assemblies and the SP photoisomerization rates. Pertinent structure/property relationships have been evidenced from the combination of X-ray crystallographic and spectroscopic techniques. Some of these systems are remarkably bistable and are very promising for potential high density optical data recording. In the second approach, neutral SP and SN molecules have been covalently linked onto POM units in new photochromic and electrochromic dyads [2][3]. This grafting allows improving the photoisomerization of the SP and SN moieties, and solid materials with strong photoresponses can be elaborated from spiro-derivative molecules initially nonphotochromic in the crystalline state. [1] K. Hakouk, O. Oms, A. Dolbecq, J. Marrot, A. Saad, P. Mialane, H. El Bekkachi, S. Jobic, P. Deniard, R. Dessapt, J. Mater. Chem. C 2013, DOI:10.1039/C3TC31992J [2] O. Oms, K. Hakouk, R. Dessapt, P. Deniard, S. Jobic, A. Dolbecq, L. Nadjo, B. Keita, J. Marrot, P. Mialane, Chem. Commun. 2012, 48, 12103 [3] A. Parrot, G. Izzet, L.-M. Chamoreau, A. Proust, O. Oms, A. Dolbecq, K. Hakouk, H. El Bekkachi, P. Deniard, R. Dessapt, P. Mialane, Inorg. Chem. 2013, 52, 11156

Authors : A. Kuzmin1, A. Anspoks1, A. Kalinko2, J. Timoshenko1, R. Kalendarev1
Affiliations : 1 Institute of Solid State Physics, University of Latvia, Kengaraga street 8, LV-1063 Riga, Latvia; 2 Synchrotron SOLEIL, l'Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette, France

Resume : Stannous tungstate SnWO4 is very interesting semiconducting material and is a promising candidate for sensing, photocatalytic and transparent conducting oxide applications. It has two polymorphs, the low-temperature orthorhombic alpha-phase and high-temperature cubic beta-phase, which transform into each other by a diffusion-controlled phase transition mechanism, whose details still require clarification. The crystalline structure of alpha-SnWO4 is composed of distorted SnO6 and WO6 octahedra, which are joined by vertices into 2D-sheets held together by Sn2+ ions. In beta-phase, which is metastable at room temperature, the structure is built up of slightly deformed WO4 tetrahedra interconnected with four strongly distorted SnO6 octahedra. The distortion of metal-oxygen octahedra in SnWO4 is caused by the second-order Jahn-Teller effect, and the type (n or p) of its conductivity can be controlled by changing the Sn:W ratio. In this study we will discuss the above mentioned issues based on the results of synchrotron radiation x-ray absorption spectroscopy, Raman scattering study and the first principles calculations.

Authors : K. P. O’Donnell, P. R. Edwards,M. J. Kappers, K. Lorenz, E. Alves and M. Boćkowski
Affiliations : Strathclyde U.; Cambridge U.; IST-CTN; Unipress

Resume : Rare-earth-doped III-N semiconductors have been studied for many years on account of their possible role in visible light-emitting diodes (LED) with built-in utility as red (e.g. Europium), green (Erbium) and blue (Thulium) monochromatic light sources [1]. However, to date, no commercial devices have been introduced on the basis of these materials. We have recently discovered photochromism and thermally activated luminescence hysteresis in the emission spectrum of p-type GaN thin films that were co-doped with Mg and Eu [2]. We have also reported an unexpected Zeeman splitting and xray-induced magnetic moment of Eu3+ ions in GaN [3,4]. These findings encourage speculation on taking the study of RE-doped III-N beyond the limited goal of im-proving LED efficiency into the realm of novel quantum-optical and magneto-optic devices, leaving aside their optoelectronic functionality. In this talk I will describe the spectroscopy of ion-implanted and annealed GaN(Mg): Eu samples and discuss the possible exploitation of the Mg acceptor in GaN as a qubit. [1] K. P. O’Donnell and V. Dierolf (eds), Topics in Applied Physics 124, (Springer, Dordrecht, 2010) [2] K. P. O'Donnell, P. R. Edwards, K. Lorenz, E. Alves, and M. Boćkowski, Proc. ICNS10, Washington, 2013, to be published in pss(c) (2014) [3] V. Kachkanov, K.P. O’Donnell, C. Rice, D. Wolverson, R.W. Martin, K. Lorenz, and E. Alves, MRS Proceedings 1290–i03–06 (2011) [4] V. Kachkanov, G. van der Laan, K. P. O’Donnell et al. Scientific Reports 2, 969 (2012)

Authors : Eric Daniel Głowacki, Dominik Farka, Elisa Tordin, Gundula Voss, Niyazi Serdar Sariciftci
Affiliations : Linz Institute for Organic Solar Cells (LIOS), Physical Chemistry, Johannes Kepler University Altenbergerstrasse 69, A-4040 Linz, Austria

Resume : We report on the photophysics of highly-soluble N,N’-di(t-butoxy carbonyl)indigos (BOC-indigos), finding that reversible photochemical trans-cis and cis-trans isomerization reactions proceed with high quantum yields (0.20 – 0.50). Absorption of wavelengths in the 550-600 nm region induces trans-cis isomerism, while blue light (~420 nm) leads to the reverse cis-trans process. We find that like their parent indigos, trans-BOC-indigos have low fluorescence yields (~1×10-3), while the cis isomers have no measurable emission. Electron donors and proton donors are both found to strongly quench photoisomerization. Observation of quenching by proton donors supports the model of ultrafast proton transfer deactivation of excited states in indigoid molecules. Dissolution of the dyes in glassy polymer matrices does not significantly impede photoisomerization – with this we demonstrate simple photochromic polymeric films. Reversible photoisomerism induced by relatively low-energy photons (~2 eV) is the dominant photophysical process in these materials, making BOC-indigo derivatives interesting for photomechanically-actuated materials.

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Authors : Francesca Martina, Carlo Baldisserri, Marina Serantoni
Affiliations : TRE – Tozzi Renewable Energy, R&S Fotovoltaico, via Zuccherificio 10, 48123, Mezzano (RA), Italia

Resume : Electrochromic films, able to change their color upon application of small electrical potentials, are promising candidates for smart window systems. The latter are used for the dynamic control of the amount of solar radiation entering buildings, thus reducing heating from solar irradiation in the hot season while ensuring adequate levels of illumination. The active electrochromic layer usually consists of an inorganic transition metal oxide such as WO3. Our activity focuses on the fabrication of time-durable, fast-switching electrochromic devices produced by simple and low-cost manufacturing processes. In order to ensure low production costs and industry-standard durability, all materials were deposited by screen printing, and glass frit was used as sealing material. Tungsten hexachloride was used as the starting material in ain-house low-temperature ethanolysis process to obtain a stable, light-yellow and transparent screen-printable paste. 500 nm-thick transparent electrochromic layers were then obtained by annealing the screen printed layers. An in-house GF paste was screen-printed to obtain the sealing pattern of the devices, while platinum counter-electrodeswere screen-printed from a commercial platinum paste. An electrolyte containing lithium ions and the redox couple I-/I3-(ion storage layer) provides the necessary Li+ source for fast coloring/bleaching of the electrochromic layer. Changes in optical density were evaluated through time-drive spectrophotometric analysis, while coloring current and charge densities were recorded through chrono-amperometry and chrono-coulometry measurements. Our future activities will be focused on the integration ofdye-sensitized solar cells (DSSCs) and electrochromic cellsto produce self-powered smart windows.

Authors : Özlem Duyar Coşkun(1), Selen Demirel(1,2 ), Gizem Durak(1,3)
Affiliations : (1) Hacettepe University, Department of Physics Engineering, Thin Film Preparation and Characterization Laboratory, Ankara, Turkey (2) Hacettepe University,Nanotechnology and Nanomedicine Division, Ankara, Turkey (3) Ankara University, Department of Physics Engineering,Ankara, Turkey

Resume : Nb2O5thin films were prepared on the 1737F glass substrate and ITO coated glass substrate by RF magnetron sputtering using a Nb2O5circular disk target in an Ar atmosphere. The argon pressure was changed between 3 – 15 mTorr during the filmdeposition. The RF power was maintained at 75 W. The substrate temperature was 300 oC.Kim Oscillator Model was used to determine the wavelength dependence of refractive index n (λ) and extinction coefficient k (λ) andfilm thickness by fitting the optical transmission and reflection measurements of the films over the spectral range from 350 to 1100 nm at 30˚ of angle of incidence simultaneously.The electrochemical and optical absorption measurements of the films were done by an electrochemical analyzer equipped with three electrode cells (using Pt as counter electrode and Ag/AgClKOH as reference electrode in 0.1 M LiClO4/PC electrolyte) and a diode array spectrophotometer during the bleaching and coloration process concomitantly. All as-deposited Nb2O5 thin films were amorphous, transparent and had more than 90% transmission in the visible and near IR region of the spectrum. The refractive index of the films was decreasing from 2.29 to 1.99 with increasing deposition pressure as a result of loose-packing film density. The colouration efficiency of the films were recorded varying between 10.20 to 33.18 cm2/C. The film prepared at 6 mTorrAr pressure has the best electrochromic performance with a colouration efficiency of 33.18 cm2/C and an optical modulation of 59% between +2V (bleached state) and -2V (coloured state). Acknowledgement This work was supported by the Scientific and Technological Research Council of Turkey (Project Number: 111T252).

Authors : C. Tchiffo-Tameko (1), C. Cachoncinlle (1), E. Millon (1), C. Boulmer-Leborgne (1), J. Perriere (2,3), M. Nistor (4)
Affiliations : 1) GREMI, UMR 7344 CNRS-Université Orléans, 45067 Orléans Cedex 2, France; 2) Sorbonne Universités, UPMC Université Paris 06, UMR 7588, INSP, 75005, Paris, France 3) CNRS, UMR 7588, INSP, 75005, Paris, France 4) NILPRP, L 22 P.O. Box. MG-36, 77125 Bucharest-Magurele, Romania

Resume : Titanium dioxide-based thin films find applications on a large number of devices and components: optical waveguides, piezoelectric transducers, gas sensors, transparent conductive electrodes. TiO2 can be doped by rare-earth elements such as Nd, that leads to intense emissions in IR domain under UV excitation making such films very promising candidates as optically active electrodes for photonic conversion by down-shifting process in silicon based solar cells. Nevertheless the electrical conductivity of Nd-doped TiO2 films has to be improved to be used as a transparent conductive electrode. In this work we attempt to increase the conductivity of Nd-doped TiO2 films by doping with a metal element (i.e. Nb). The Nb/Nd-codoped TiO2 films were grown by nanosecond pulsed-laser deposition. The doping concentration, composition, structure, microstructure and morphology of films were precisely studied. These results are correlated with optical (transparency, photoluminescence under UV excitation) and electrical (resistivity, concentration and mobility of charge carriers) properties.

Authors : M. Kodu, T. Arroval, T. Avarmaa, R. Jaaniso, I. Kink, S. Leinberg, K. Savi, M. Timusk
Affiliations : Institute of Physics, University of Tartu, Riia 142, 51014 Tartu, Estonia

Resume : Polycrystalline c-axis oriented ZnO:Al (AZO) thin films were deposited onto amorphous SiO2 substrates by pulsed laser deposition (PLD) method. Films were deposited at 300 oC in vacuum and oxygen environment using targets doped with 1-10 at% Al. The properties of thin films were studied from the standpoint of transparent electrode applications. According to XRD analysis, Al doping level and deposition atmosphere does not have considerable influence on crystalline quality of our AZO films. As determined by XRF analysis, Al concentration in the films was substantially lower than nominal Al concentration in ZnO:Al PLD targets. Compared to the films grown in oxygen, films deposited in vacuum environment had substantially lower resistivity (σ) and showed significantly different σ dependence on Al concentration – oxygen-deposited films had minimal σ at 0.6 % Al doping concentration, compared to 4.3 % for vacuum deposited films. Also, the carrier concentration (ne) and mobility (μ) dependence on Al doping level were considerably different – a) at all doping levels, ne of vacuum deposited films was higher than of films deposited in oxygen, b) carrier mobility of oxygen deposited films decreased steadily with the increase of Al doping from 0.6 to 5.2 % (μmax at 1% Al) but for vacuum deposited films, mobility was highest at 2.8 % doping level. The results can be explained by higher effective solubility of Al for the films deposited in vacuum conditions. Oxygen deposited films showed high optical transmittance in the visible and near-IR region while transmittance of the vacuum deposited films decreased in near-IR region due to increased reflectance caused by larger carrier concentrations in these films.

Authors : M. Nistor 1, E. Millon 2, C. Cachoncinlle 2, W. Seiler 3, N. Jedrecy 4,5, C. Hebert 4,5, J. Perrière 4,5
Affiliations : 1 National Institute for Lasers, Plasma and Radiation Physics (NILPRP), L22 P.O. Box. MG-36, 77125 Bucharest-Magurele, Romania; 2 GREMI, UMR 7344 CNRS-Université d’Orléans, 45067 Orléans Cedex 2, France; 3 PIMM, UMR CNRS 8006 Arts et Métiers ParisTech, 151 Boulevard de l’Hopital, 75013 Paris, France; 4 Sorbonne Universités, UPMC Univ Paris 06, UMR 7588, INSP, F-75005, Paris, France; 5 CNRS, UMR 7588, INSP, F-75005, Paris, France

Resume : The ZnO films properties can be enhanced or new properties can be obtained by the use of well adapted dopants. For example Nd can be used to increase the ZnO conductivity (Nd3+ in substitution of Zn2+) and to convert the solar spectrum (down conversion of UV photons in near IR photons), or to induce magnetic properties. Transparent Nd doped ZnO (ZnO:Nd) thin films were grown either by pulsed-laser deposition (PLD) or pulsed-electron beam deposition (PED) on Si and c-cut sapphire single crystal substrates at various oxygen pressures and substrate temperatures. The composition, surface morphology and structure of Nd doped ZnO thin films were investigated by means of Rutherford Backscattering Spectrometry, SEM and X-ray diffraction analyses. The ZnO:Nd films are smooth, dense, with the wurtzite phase. Epitaxial relationships between films and c-cut sapphire substrates were evidenced by asymmetric X-ray diffraction measurements. These results have been correlated with optical and electrical measurements. A dielectric model including band gap transitions and free electron excitations was used to simulate the transmittance spectra of ZnO:Nd films in 300-2500 nm range. The resulting optical parameters were compared with those obtained by Hall effect measurements for different growth conditions and Nd doping concentrations.

Authors : N. Law, H. Schreuders, B. Dam
Affiliations : MECS, Chemical Engineering, TU Delft, Netherlands

Resume : In a recent study the photochromic properties in reactively sputtered yttrium hydride thin films were reported [1]. The incorporation of a substantial amount of oxygen appeared vital for the observation of this effect. Exposure to visible and ultraviolet (UV) light at moderate intensity triggers a uniform decrease in the optical transmission of visible and infrared (IR) light. The reaction is reversible and samples that are left in the dark return to the initial transparent state. Potential applications range from smart windows to sunglasses. The effect observed in YOyHx is unique, since it shows reversible photochromism induced by light from the visible part of the optical spectrum and displays colour neutrality: The transmission decreases for all wavelengths with energies E < Egap. This suggests some opto-electronic phase segregation of metallic entities in a dielectric matrix. Here, we investigate the wavelength dependence of the photochromism on samples with slightly varying bandgaps. We observe in all case a substantial darkening at wavelengths below the gap. References 1. T. Mongstad, C. P. Bjorkman, J. P. Maehlen, L. P. A. Mooij, Y. Pivak, B. Dam, E. S. Marstein, B. C. Houback, S. Zh. Karazhanov, Sol. Energy Mater. Sol. Cells 95 (2011) 3596.

Authors : Y. Wang1, J. Ghanbaja1, S. Migot1, P. Boulet1, P. Miska1, D. Horwat1, F. Soldera2, F. Mücklich2, J.F. Pierson1
Affiliations : 1 Institut Jean Lamour, Université de Lorraine, Nancy, France 2 Department of Materials Science, Saarland University, Saarbrücken, Germany

Resume : The binary Cu-O system contains two stable phases (Cu2O and CuO) and one metastable phase (Cu4O3) that may be suitable as p-type TCO. These three copper oxides can be deposited by adjusting the oxygen flow rate introduced into the sputtering chamber. Although some of the properties of the Cu4O3 phase have been described, the relationship between the film microstructure and their properties is scarcely described. This presentation aims to study the effect of the deposition conditions on the films microstructure and on films properties. As a function of the oxygen flow rate and the total pressure, 3 main deposition zones corresponding to the 3 oxides have been evidenced by X-ray diffraction and Raman spectrometry. Within these domains, the films exhibit a columnar microstructure. Pole figure analyses show that the texture of the 3 oxides can be tuned by adjusting the deposition parameters. For Cu2O films, the preferred orientation changes from [100] to [111] by increasing the total pressure. At the border of the 3 zones, a biphased domain has been systematically evidenced by Raman spectrometry (Cu2O + Cu4O3 or Cu4O3 + CuO). The relationship between the microstructure and the electrical and optical properties of the films is discussed. Finally, a homoepitaxial growth of Cu2O has been evidenced by transmission electron microscopy observations in cross section.

Authors : Seung Ho Han1, So Hee Kang1,2, Sang Jiun Lee1,3, Hyeongkeun Kim1, Dae Ho Yoon2, Sahn Nahm3, Woo Seok Yang1
Affiliations : 1Electronic Materials & Device Research Center, Korea Electronics Technology Institute, Korea 2School of Advanced Materials Science and Engineering, Sungkyunkwan University, Korea 3Department of Materials Science and Engineering, Korea University, Korea

Resume : Electrochromic materials, which can reversibly change their optical properties under an applied electric field, have attracted in various applications such as smart windows, optical displays and rear-view mirrors. Electrochromic devices (ECDs) contain an electrochromic film in contact with an electrolyte adjacent to an ion storage layer, and these three layers are sandwiched between the two transparent conducting films. For the simple and large-scale fabrication, ECDs which consist of all solid-state materials are advantageous. In this study, monolithic solid-state form of ECDs was fabricated on single glass substrate by magnetron sputtering. The ECDs exhibited the multilayer structure of ITO/WO3/Ta2O5/NiO/ITO on glass substrate. The WO3, Ta2O5 and NiO were used as electrochromic, solid electrolyte and ion storage layer, respectively. Sputtering conditions, such as DC/AC power, Ar/O2 gas flow rate and deposition time were optimized for the enhanced performance of ECDs. The cyclic voltammetry was performed using a potentiostat with a standard three-electrode configuration. The WO3 and NiO films were deposited on ITO glasses served as the working electrodes, respectively. Pt was used as the counter electrode, Ag/AgCl was the reference electrode and the electrolyte was 1M LiPF6/PC. The transmittance spectrum of as prepared and after colored ECDs was characterized by a UV/VIS/NIR spectrophotometer.

Authors : Isil Top1, Halime S. Kocadag, Elif Kilic, and Mehmet A. Gulgun
Affiliations : 1Isil Top, Faculty of Engineering and Natural Sciences, Sabanci University, Tuzla, Istanbul, 34956, TURKEY. Halime S. Kocadag,Faculty of Engineering and Natural Sciences, Sabanci University, Tuzla, Istanbul, 34956, TURKEY. Elif Kilic, Faculty of Engineering and Natural Sciences, Sabanci University, Tuzla, Istanbul, 34956, TURKEY. Mehmet A. Gulgun, Faculty of Engineering and Natural Sciences, Sabanci University, Tuzla, Istanbul, 34956, TURKEY. Halime S.Kocadag,Elif Kilic, Mehmet A. Gulgun,

Resume : Oxides of certain transition metals show reversible colour change as a function of temperature. The so-called thermochromism was observed in CoAl2O4-Bi2O3 blends, in TiO2- V2O5 and V2O5-Nb2O5 systems. The three separate systems studied in this work show reversible thermochromism in the temperature range of 150 °C to 500 °C. All three systems exhibited hysteresis behaviour in their transition temperature. CoAl2O4-Bi2O3 blends allowed a certain degree of tuning for the transition temperature. As the ratio of the CoAl2O4:Bi2O3 was increased, the temperature of perceived colour change shifted to higher temperature from 200 °C to 400 °C. The V0.48Ti0.52O2 oxide system show reversible colour change (yellow to deep orange) in the temperature range 150-160 °C with the smallest hysteresis in the transition temperature. The phase analysis of the oxide powders were done by using XRD and electron diffraction studies. The origin of thermochromism was investigated with the help of the UV-VIS Spectroscopy and electron microscopy.

Authors : Vytautas Astasauskas, Aleksandras Iljinas, Vytautas Stankus, Brigita Abakeviciene
Affiliations : Department of Physics, Kaunas University of Technology, Studentu str. 50, LT-51368 Kaunas, Lithuania

Resume : Nickel oxides thin films and especially one form NiO (bunsenite) are very promising and useful material due it interesting properties which allow to use it in such applications as antiferromagnetic films, chemical and gas sensors, cathodes of batteries, catalyst, varistors and electrochromic devices, called “smart glass”. Our work is focused on synthesis NiO thin films, which could be useful for one of these devices elements. Problems to get quality NiO films using magnetron sputtering are lying in some aspects. The main is that Ni cathode is ferromagnetic. It complicates sputtering process due to shortening magnetic field lines on magnetron surface and causes instabilities in plasma processes. The synthesis of nickel oxide thin films using reactive magnetron sputtering technique and post annealing in atmosphere as deposited films were analyzed in this work. Nickel oxide electrical, optical, crystallographic and surface morphology properties before annealing and after were measured and analyzed. Comparing as deposited properties of films before annealing and after the conclusions were made, that nanocrystal Ni2O3 phase grows during deposition, but after annealing in 550oC temperature (50 min) this phase transforms to quality nanocrystal NiO films.

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Thermochromism II : Harlan Byker, Bernard Dam
Authors : Michael E.A. Warwick, Russell Binions
Affiliations : Warwick Department of Chemistry, University College London, Christopher Ingold Laboratories, 20 Gordon Street, London, WC1H OAJ, United Kingdom. & UCL Energy Institute, Central House, 14 Upper Woburn Place, London, WC1H 0HY, UnitedKingdom. Binions School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London, E1 4NS, United Kingdom.

Resume : Thin films of thermochromic vanadium dioxide were deposited using a novel electric field assisted chemical vapor deposition methodology at atmospheric pressure onto glass substrates. Electric fields were generated during the deposition reaction by applying a potential difference across the inter-digitated electrodes of the gas sensor substrate or buy applying an electric field between two transparent conducting oxide coated glass substrates. The deposited films were analyzed and characterized using scanning electron microscopy, Raman spectroscopy, X-ray diffraction, atomic force microscopy, variable temperature optical spectroscopy and contact angle measurements. It was found that applying an electric field led to large changes in film microstructure, preferential orientation and changes in the film growth rate. This led to significant changes in materials properties such as decreased crystallite size, nano-structuring, increased surface roughness and enhanced wetting behavior. The deposited films were evaluated using Energy Plus for their energy demand reduction characteristics in a variety of architectural settings and compared against existing glazing products. It was found that thermochromic thin films can offer significant energy demand reduction benefits.

Authors : A. Corvisier, F. Capon, J.F. Pierson
Affiliations : Institut Jean Lamour, Université de Lorraine, Nancy, France

Resume : Vanadium dioxide (VO2) is a thermochromic material that presents an abrupt first order phase transition at the critical temperature (Tc) of 68 °C. VO2 thin films have been deposited using reactive sputtering on silicon substrates using three kinds of processes. In the first one, the films have been deposited at high temperature as usually encountered in the literature. In the second process, the VO2 coatings have been synthesised in a two steps method: deposition at room temperature followed by an ex situ annealing in air. Finally, the last process studied can be described as the deposition at room temperature of a VO2 layer covered by a thin film of silica and the air annealing of this bilayer. High temperature deposited films are well crystallized and exhibited a pronounced metal insulator transition at 68°C. On the other hand, the films deposited at room temperature are X-ray amorphous and do not exhibit a thermochromic effect. Furthermore, an oxidation of the films occurs during the air annealing of the vanadium oxide layer. Such oxidation step is avoided by the use of the silica layer that acts as a barrier for oxygen diffusion. The monitoring of the bilayer crystallization by X-ray diffraction shows that the crystallisation occurs at temperature as low as 330 °C and that the crystallisation is governed by a two dimensional growth mechanism. The crystalline bilayer films clearly exhibit switching properties in the infrared domain at a temperature close to 68 °C.

Authors : D. Vernardou 1, D. Louloudakis 1 2, N. Katsarakis 1 3 4, E. Koudoumas 1 3, I. I. Kazadojev 5, S. O’Brien 5, I. M. Povey 5, M.E. Pemble 5
Affiliations : 1 Center of Materials Technology and Photonics, School of Applied Technology, Technological Educational Institute of Crete, 710 04 Heraklion, Crete, Greece; 2 Department of Physics, University of Crete, 710 03 Heraklion, Crete, Greece; 3 Electrical Engineering Department, Technological Educational Institute of Crete, 710 04 Heraklion, Crete, Greece; 4 Institute of Electronic Structure and Laser, Foundation for Research & Technology-Hellas, P.O. Box 1527, Vassilika Vouton, 711 10 Heraklion, Crete, Greece; 5 Tyndall National Ιnstitute, University College Cork, Lee Maltings, Prospect Row, Cork, Ireland.

Resume : The interest in electrochromic vanadium oxide coatings has increased during the last few years, because of their use in windows that can control the solar light transmission, contributing therefore significantly to energy saving in buildings. Large area uniformity, low production cost and durability of the coatings can play a very important role in the fabrication of such “smart” windows. In that respect, an aerosol assisted chemical vapor deposition process is more advantageous over the other conventional techniques, which are already used in industry for the fabrication of these coatings. Since, it is easily integrated to float glass plants, no expensive vacuum systems are required and high production rates may be realised. In this paper, the effect of the growth parameters and coating thickness on the structural and morphological characteristics of vanadium pentoxide are considered. Finally, their electrochemical activity, comprising charge storage capability and corresponding specific capacitance, reversibility and repeatability of the charge transfer through the as-deposited and annealed vanadium oxides are investigated.

L.L XI.4

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