Ta doped tungsten oxide nanopowder can be applied for producing electrochromic film. The Ta doping tungsten oxide electrochromic film has better electrochemical stability and proton conductivity than the tungsten trioxide electrochromic film. This is because Ta2O5 has excellent ion and proton conductivity properties and can be used as an electrolyte layer or a protective layer material in an electrochromic device to solve the problem that the tungsten trioxide is easy to dissolve in the proton electrolyte to limit its application in electrochromic device – a device using proton-type electrolyte as a conductive layer.
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However, although Ta2O5 has excellent proton conductivity, its electronic conductivity is poor. So, excessive Ta doping will greatly reduce the electronic conductivity of tungsten oxide. The coloring/color fading performance of the tungsten oxide film is achieved by co-injection/extraction of electrons and protons. If the electronic conductivity is greatly reduced, the proton transfer performance will be impeded. Therefore, the proton transporting ability of the tungsten oxide film doped with excess Ta is weakened, and the coloring efficiency is also lowered.
