Tungsten Trioxide Electrochromic Thin Film
Tungsten trioxide(WO3) is one of the mostly studied cathode coloring electrochromic material, tungsten trioxide electrochromic thin film is a kind of inorganic electrochromic material which has advantages of low cost, cyclic reversibility, optical property and fast color-changing speed. WO3 electrochromic thin film is widely applied in smart window and car mirror.
Tungsten trioxide electrochromic thin film can be produced by physical vapor deposition, chemical vapor deposition, electron beam evaporation method and so on. The most widely used method is electronic beam evaporation method, the evaporation material can either be WO3 or WO3 target.
Tungsten Trioxide Electrochromism Mechanism
The most widely applied is valence transition theory came up by Faughnan. Under effect of applied extra electric field, electron and anions goes into WO3 from both side of thin film, electron is captured by W atom and forms into localized states. Metal ion M+ stays in this area and forms into dark blue tungsten bronze(MxWO3). W ion in MxWO3 with different valance state, electron transit between different valence state of W atom which leads to color change of WO3 thin film.
WO3(Colorless) +xM++xe→MxWO3（Dark Blue）
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