Advanced electrochromic devices based on WO 3 thin films (original) (raw)
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Study of WO3 films with textured surfaces for improved electrochromic performance
Solid State Ionics, 2001
We present a study of electrochromic (EC) devices based on WO thin films with textured surfaces. Surface patterns were 3 generated by electron gun deposition of WO stripes (173-mm wide and 150-nm high) on a previously grown 'flat' WO 3 3 film, 150-nm thick. The films were characterized by SEM, XPS and FTIR. They are amorphous and near-stoichiometric and have a packing density of 0.8. The textured films were used for the fabrication of EC devices of the configuration: K-glass / WO / 1 M LiClO in PC / K-glass. These devices were characterized by optical and electrochemical techniques such 3 4
Comparative study of the electrochromic properties of WO3 thin films
Displays, 1988
This paper deals with a comparison between the electrochromic properties of tungsten oxide obtained by vacuum evaporation of WO 3 powder, anodic oxidation of W sheets and thermal oxidation of tungsten oxides obtained by chemical vapour deposited (CVD) onto SnO 2 substrate. Good electrochromic performances have been obtained with CVD layers despite their polycryst~llirte morphology and also with anodic oxidized W sheets despite the stoichiometry of the material. The results are compared with those obtained with amorphous tungsten oxide films prepared by vacuum evaporation. Moreover, we have shown that the electrochromic properties of the oxide (colouring efficiency, switching speed) depend on the nature of the substrate used. An AC complex impedance measurement was used to show the influence of this substrate on the behaviour of the electrical interfaces.
Efficient electrochromic performance of nanoparticulate WO3 thin films
Journal of Materials Chemistry C, 2013
This report highlights the suitability of electrodeposited nanoparticulate-WO 3 (NP-WO 3 ) electrodes for transmissive electrochromic devices (ECDs). The WO 3 electrodes in the form of thin films are composed of 10-20 nm nanoparticles. An electrochromic (EC) device of dimensions 5 Â 4 cm 2 fabricated using NP-WO 3 showed an Li insertion coefficient (x) of 0.43, which resulted in highest photopic transmittance modulation (88.51%), better Li-ion diffusion coefficient ($3.16 Â 10 À9 cm 2 s À1 ), fast electrochromic response time (5.2 s for coloration and 3.7 for bleaching) and excellent coloration efficiency ($137 cm 2 C À1 ). On reduction of WO 3 , the CIELAB 1931 2 color space coordinates show the transition from colorless to the deep blue state (Y ¼ 97, a* ¼ À1.93, b* ¼ 0.46 and Y ¼ 10, a* ¼ 1.57, b* ¼ À41.01) with steady decrease in relative luminance. † Electronic supplementary information (ESI) available: Cross-sectional view of SEM, EDS spectra, and L*a*b* system of colorimetric analysis. See
Materials Chemistry and Physics, 2010
The phenomenon of electrochromism in tungsten trioxide (WO 3 ) thin films has recently attained considerable interest due to their enormous applications in inorganic thin film electrochromic devices. We have investigated the compositional, optical, and electrochromic properties of the WO 3 thin films grown at different substrate temperatures by the thermal evaporation of WO 3 powder. The thin films were characterized using X-ray diffraction (XRD), X-ray photo-emission spectroscopy (XPS), and electrochemical techniques. The XPS analysis suggested that the oxygen to tungsten (O/W) ratio decreases, i.e., the oxygen deficiency increases, on increasing the substrate temperature up to 500 • C. The electrochemical analysis provided a comparative study of the coloration efficiency (CE) of the WO 3 thin films intercalated with three different ions viz. H + , Na + , and K + . The effect of the variation of the substrate temperature on the CE and the switching time have also been investigated for the WO 3 thin films intercalated with H + ions; the thin films deposited at RT and intercalated with H + ions are found to possess adequate electrochromic properties viz. CE and switching time from device point of view.
Review on electrochromic property for WO3 thin films using different deposition techniques
Materials Today: Proceedings, 2016
Thin film technology plays an important role in technological development and recent research in engineering. Recent developments in the synthesis of transition metal oxides in the form of porous thin films have opened up opportunities in the construction of electrochromic devices with enhanced properties. The general applications of thin films are in the field of optoelectronics, microelectronics, etc. There are numbers of different techniques used for the deposition of stable thin films of oxide materials. The transition metal oxides like WO 3 and MoO 3 have good electrochromic properties and these oxides can also change their optical properties when the voltage pulse applied. These electrochromic materials are used for displays, rear-view mirrors and smart windows for energy saving and gas sensors. Tungsten Oxide (WO 3) is the best suited material for energy conservation applications due to its better coloration efficiency. Thin films of WO 3 are deposited by various techniques like physical vapour deposition, chemical vapour deposition, sol-gel method, magnetron sputtering methods. Out of this some methods like magnetron sputtering method offers good flexibility for deposition and allow to fabricate required topographical, physical, crystallographic, desired geometrical and metallurgical structures. This paper is aimed to summarize applications of WO3 thin films as electrochromic material and the effect of various deposition techniques on electrochromic and optical properties of WO3 thin films.
Journal of Electronic Materials, 2018
In the current study, composites of tungsten trioxide (W0 3) and silver (Ag) are deposited in a layer-by-layer electrochromic (EC) arrangement onto a fluorinedoped tin oxide coated glass substrate. Tungsten oxide nanoparticles are an ntype semiconductor that can be used as EC cathode material. Nano-sized silver is a metal that can serve as an electron trap center that facilitates charge departure. In this method, the WO 3 and Ag nanoparticle powder were deposited by physical vapor deposition onto the glass substrate. The fabricated electrochromic devices (ECD) were post-annealed to examine the effect of temperature on their EC properties. The morphology of the thin film was characterized by scanning electron microscopy and atomic force microscopy. Structural analysis showed that the addition of silver dopant increased the size of the aggregation of the film. The film had an average approximate roughness of about 17.8 nm. The electro-optical properties of the thin film were investigated using cyclic voltammetry and UV-visible spectroscopy to compare the effects of different post-annealing temperatures. The ECD showed that annealing at 200°C provided better conductivity (maximum current of about 90 mA in the oxidation state) and change of transmittance (DT = 90% at the continuous switching step) than did the other thin films. The optical band gaps of the thin film showed that it allowed direct transition at 3.85 eV. The EC properties of these combinations of coloration efficiency and response time indicate that the WO 3-Ag-WO 3-Ag arrangement is a promising candidate for use in such ECDs.
Journal of The Electrochemical Society, 2006
In this investigation, the effect of coloring voltage and thickness on optical and also electrochromical properties of WO 3 thin films has been studied. The WO 3 thin films were grown on glass and indium tin oxide coated conducting glass substrates by e-beam evaporation at different thicknesses of 200, 400, and 700 nm. Optical properties of the deposited samples were characterized in the ultraviolet-visible range ͑300-1100 nm͒. The optical bandgap energy of the WO 3 was obtained in a range of 3.3-3.5 eV showing its increase by decreasing the film thickness. The refractive index of the WO 3 films was measured around 2 in the visible range. Surface chemical states of the films were studied by X-ray photoelectron spectroscopy, which showed the stoichiometry of our deposited tungsten oxide thin films is acceptable. Atomic force microscopy was used for studying surface morphology of the deposited films. The electrochromic properties of the WO 3 films were characterized using a lithium-based electrolyte. It was shown that there is an optimum coloring voltage for each film thickness, which maximizes the change in optical density during electrochromic process. The coloration efficiency of the samples at the optimum voltage was linearly improved by increasing the film thickness at a constant wavelength ͑500 nm͒.
Thin Solid Films, 2019
The development of an uncomplicated process for the preparation of tungsten oxide (WO 3) nanorods (NRs) using hydrothermal method is still underway. Thus, this study demonstrated the growth of WO 3 NRs on indium tin oxide (ITO) coated glass substrates in aqueous solution using single synthesis step hydrothermally. The surface area and size of the NRs which should be tunable for electrochromic (EC) applications were controlled by adjusting the concentration of surfactants such as propylene glycol (PG). The synthesized NRs were illustrated using crystal structure study, surface morphology, chemical analysis, and the measure of the luminance of a color. The results manifested that increasing the PG content increased the size of the crystallite with a nanoparticle-like morphology on the ITO substrate, indicating the direct deposition of a stable WO 3 thin film. In addition, the synthesized WO 3 NRs exhibited fast switching speed and high contrast ratio implying superior EC properties for smart window application. Furthermore, an EC device with the dimensions of 2×4 cm 2 was assembled using the synthesized WO 3 NRs with the ITO/WO 3 /Lithium perchloratepropylene carbonate-poly(methyl methacrylate)-acetonitrile/nickel oxide/ITO configuration. The device had an average optical modulation in the visible region, a fast EC response time (1.2 s for coloration and 1.5 s for decoloration), excellent coloration efficiency (243 cm 2 C-1) and a superior EC stability (over 20000 color/decolor cycles).
Study of electrochromic cells incorporating WO, MoO, WO-MoO and VO coatings
Thin Solid Films, 1999
We studied eiectrochromic ceils incorporating evaporated W03, X1003 and mixed W00+lo03 thin films as electrochrwnic layers. Lil doped V20s films served as an ion siorage layer. The devices exhibit good optical properties with very low luminous iransmittance values in the colored state, which make them suitable for Iarge-area window applications. Addition of F'201 films as an ion storage Iayer was found to improve the cell coloration performance up to 74%. Q 1999 Elsevier Science S,k iv1 rights reserved.
Preparation and characterization of WO3-based electrochromic cell system
Chemical Vapor Deposition (CVD) technique has been used for fabrication of tungsten oxide (W03) films. An electrochromic device (ECD), using CVD-W03 as an electrochromic electrode has been prepared in combination with ion conductive polymer thin films, properly charged with H+ or tr, by using H3P04 or LiCI04. Optical modulation of about 50% at 600 nm in transmittance mode and time response of30 sec. are obtained.