| As an N-type semiconductor material, the structure of tungsten oxides isA+-deficient perovskite(ABO3) with an unit of WO6octahedron. WO3film can turnblue in color by applying suitable negative electrical voltage, which induces thecations to insert into the host material for forming color centers. The electrochromicperformance of WO3are greatly affected by the kind of crystal lattice andmicro-morphologies. Compared with the crystalline WO3with a denser structure,amorphous WO3demonstrates larger optical modulation, shorter switching time andhigher coloration efficiency due to its porous structure which can provide morechannel for ions diffusion. But the poor structural of amorphous WO3leads todissolution in electrolytes, resulting in poor electrochromatic stability.In this work, amorphous WO3thin films were deposited by thermal evaporation,and as-deposited films were proved by SEM. A favorable preparation condition of thefilms was investigated by changing evaporation time, pressure and current. Finally weprepared films with fine electrochromatic properties. To further improve theperformance, we pre-coated the FTO substrate with nano-silver particle by thermalevaporation.Our findings include:1. Our results show a modestly raised current can increase response timessignificantly, because higher current can decrease the WO3film resistance whileimproving the contact between particles.2. An modestly raised pressure can increase response times and opticalmodulation of WO3significantly.3. The WO3film prepared under the condition of pressure at30mpa and currentat120A exhibited a large optical modulation(83.4%), a fast response(tc=6.4s,tb=1.7s)and a high coloration efficiency(118.4cm2/C).4. Ag greatly improves the stability of amorphous WO3film, maintaining theadvantages of the optical modulation(82.8%) and fast response(tc=6.9s,tb=1.7s). However, the coloration efficiency is reduced, due to the composite structureimproving the film capacitance. |
PDF Full Text Request