Ta doped tungsten oxide can be used to prepare electrochromic film. And the Ta doping tungsten oxide electrochromic films can be prepared by magnetron sputtering method to improve the electrochemical cycle stability of tungsten oxide electrochromic films.

Crystalline tungsten trioxide film can be prepared by magnetron sputtering deposition method and then by heat treatment. By magnetron sputtering deposition, an amorphous tungsten trioxide film is obtained, which is heated in air at 200°C, 250°C, 300°C, 350°C and 400°C and held for 30min for heat treatment. As the heat treatment temperature increases, the electrochromic properties of the amorphous tungsten trioxide film decrease. When the heat treatment temperature is higher than 350°C, the amorphous state is converted into a crystalline state.

WO3, or tungsten trioxide, can be used to prepare electrochromic film, and finally applied to architectural glass in the form of electrochromic glass, that is, smart window, to shield heat and save energy. Besides, as it has the characteristic of environmental protection, tungsten trioxide nano powder is more and more widely used in the production of electrochromic films.

MoO3 doping WO3 electrochromic film is darker in colored state and in bleached state than the pure tungsten trioxide film. This is because MoO3 itself is an electrochromic material with a color change similar to WO3. The colored state of MoO3 film is blue-violet and the bleached state is yellow. And the colored state of the pure tungsten oxide film is blue, and the bleached state is almost colorless or transparent.