Smart glass electrochromic device fabrication of uniform tungsten oxide films from its powder synthesized by solution combustion method (original) (raw)
A simple method for chemical bath deposition of electrochromic tungsten oxide films
Materials Chemistry and Physics, 2007
A simple, economical, chemical bath method for depositing tungsten oxide films has been developed. The films have been prepared from aqueous solution containing Na2WO4·2H2O and diethyl sulfate in slightly acidic media at 90–95 °C on fluoride doped tin oxide substrates (FTO). The X-ray analysis clearly showed that the films do not correspond to any known tungsten oxide with its experimental d-values and in the text the composition is denoted as WOx. The thin films durability was tested in aqueous solution of LiClO4 (0.1 mol dm−3) for about 7000 cycles followed by cyclic voltammetry which confirmed that the coated material is highly stable. The optical transmittance spectra of colored and bleached states showed significant change in the transmittance, which make these films favorable for electrochromic devices.
Iranian Journal of Physics Research, 2019
Tungsten oxide (WO3) thin layers were prepared on Fluorine Tin Oxide glass using the electrodeposition method. WO3 layers were evaluated as a function of the deposition time (480 s, 600 s, 660 s and 720 s). SEM results showed that by increasing the deposition time, a gradual decrement in cracks on their surface occurred. The electrochromic properties of the WO3 thin layers were investigated in a nonaqueous LiClO4-PC electrolyte by means of optical transmittance, cyclic voltammogram (CV) measurements. The WO3 thin layer with the deposition of time 600 s exhibited a noticeable electrochromic performance with the variation of transmittance being up to 58.26% at 633nm. The CV measurements also revealed that the WO3 thin layer with the deposition time of 600 s had a high electrochemical reaction activity and reversibility due to its highly porous structure.
Model of electrochromic and related phenomena in tungsten oxide thin films
Journal of Solid State Electrochemistry, 2003
We have developed a model of electrochromic and related phenomena in tungsten oxide thin films based on the assumption that the constitution of such films is heterogeneous and built up of nanosized particles, pores and adsorbed substances (mainly water). It is discussed why a high-efficiency reversible blue colour is observed in amorphous tungsten oxide films (α-WO3 films) as well as why such porous thin films with polycrystalline or amorphous constitution and with a variety of particle properties can be easily obtained by a physical vapour deposition process in a low-pressure atmosphere in the presence of water. A substrate temperature in the range 450–550 K corresponds to some plateau on the water desorption curves which divided physically adsorbed water from chemically adsorbed water. Two types of structural units based on tetrahedrally and octahedrally coordinated tungsten ions have the main role in the formation of the film constitution. The tetrahedral structural units have a glass-forming function, but the octahedral ones have a modification function. From the electrochemistry point of view, the internal multiphase interfaces in such films are distributed multiphase electrodes. The adsorbed water together with defects of the oxide particles provide reagents for reversible coloration reactions in the film. The colour centres can be induced thermally (oxygen nonstoichiometry) or electrically (injected ions) or by radiation (photoinjected hydrogen). The electrochromism and related phenomenon of α-WO3 films can be directly related to ion insertion/extraction processes controlled by external forces.
Studies on electrochromic smart windows based on titanium doped WO3 thin films
Thin Solid Films, 2007
Titanium doped tungsten oxide thin films have been deposited by co-sputtering metallic titanium and tungsten in the presence of argon and oxygen. The oxygen chamber pressure was varied in the range 1 × 10 − 3-4 × 10 − 3 mbar keeping the sputtering power of titanium and tungsten constant at 2 W/cm 2 and 3 W/cm 2 respectively. The effect of oxygen chamber pressure on the electrochromic (EC) properties of titanium doped WO 3 has been investigated in three steps. First, the material properties of EC film were investigated by XRD, SEM, and UV-Vis spectrophotometer; the thickness and the optical constants were estimated from the reflectance measurements. Second, the electrochromic behavior of the EC films was characterized by cyclic voltammetry (CV) using 1.0 M HCl as electrolyte. The optical modulation (ΔT) and coloration efficiency (CE) of the titanium doped tungsten oxide thin film deposited at an O 2 pressure of 4 × 10 − 3 mbar was found to be better with typical values of ΔT = 70% and CE = 66 cm 2 /C (at λ = 550 nm). Finally, EC devices consisting of five layers (Glass/ITO/Ti:WO 3 /Ta 2 O 5 /NiO/ITO) have been fabricated and tested.
Surface and Coatings Technology, 2005
A change of water vapour partial pressure from 0 to 4 Pa was carried out in order to prepare sputtered tungsten oxide compounds with various oxygen and hydrogen concentrations. Oxygen, tungsten and hydrogen concentrations were determined by Rutherford Backscattering Spectroscopy (RBS) and by Elastic Recoil Detection (ERD) analysis. Structure of tungsten oxide films was analyzed by X-ray diffraction. At low water vapour partial pressure, the films are crystallized and WO 2 and W 3 O phases were observed. The electrochromic performances of such film/SnO 2 /glass substrate system were measured and discussed taking into account the influence of the water vapour partial pressure injected into the deposition process on the structure, chemical composition and optical properties of the films. D
Influence of Dopant Concentration on the Electrochromic Properties of Tungsten Oxide Thin Films
Electrochimica Acta, 2015
In order to achieve neutral coloration suitable for smart window applications WO 3 thin films modified by V 2 O 5 doping were deposited using RF magnetron sputtering method with 100 W RF power at room temperature (RT). The influence of dopant concentration on the structural and electrochromic performance have been investigated. Amorphous structure as revealed by the surface characteristics facilitates electrochromic process. Uniformly distributed channels between the aggregated grains provide shorter path ways to enhance coloration efficiency. PL emission presented higher photonic efficiency for 2% of V 2 O 5 doped WO 3 film. Reversible color change between transparent oxidized and deep blue colored reduced state depicted faster ion intercalation / deintercalation kinetics and faster switching responses with the bleaching time of 3.3 s and coloration time of 4.1 s. Better reversibility of 59.10 %, larger photopic contrast ratio of 2.29 and greater coloration efficiency of 66.75 cm 2 C-1 at 630 nm unveiled by 2% of V 2 O 5 doping, makes the film promising for practical applications.
Investigation of electrochromic properties of nanocrystalline tungsten oxide thin film
Thin Solid Films, 2002
Thin films of tungsten oxide were grown by organometallic chemical vapor deposition (OMCVD) using tetra(allyl)tungsten, W(h -C H ) . X-Ray diffraction (XRD) analyses showed amorphous films at substrate temperatures (T ) -3508C and 3 3 5 4 s polycrystalline films at T )3508C. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) revealed grain s sizes in the range 20-40 nm. In situ electrochemical reduction of WO yITO (2.0 M HCl) produced a faint blue color in less 3.2 than 1 s. The maximum coloration efficiency (CE) was found to be 22 cm ymC at 630 nm. The density of the films decreases 2 from 4.53 to 4.29 gycm after annealing. An optical bandgap (E ) of ;3.2 eV was estimated for both as-deposited and annealed 3 g films. ᮊ
Electrochromic properties of nanocrystalline tungsten oxide thin films
Thin Solid Films, 1998
Tungsten trioxide films formed of aggregates in the nanometric range have been deposited by thermal evaporation and condensation method. From the atomic force microscopy study, the aggregate dimensions were found to be in the range between 350 nm and 450 nm. The optical, structural and electrochromic performance of these films under lithium intercalation is studied in detail and their properties are compared to those of continuous films of tungsten trioxide. The films show a slightly elevated diffuse reflectance in the lower wavelength range and a very high transmission in the solar and visible wavelengths. Under lithium intercalation, the films exhibit a very good degree of electrochromic optical modulation in both these spectral ranges and hence, are very suitable for electrochromic device application. The high degree of change between the clear state and the colored state render such nanocrystalline films more efficient in their electrochromic performance than the conventional continuous films. q 1998 Published by Elsevier Science S.A. All rights reserved.
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).