WO3 can be applied in electrochromic device. And it is mainly used as an inorganic electrochromic material or a cathode electrochromic material. According to experts, electrochromic devices have many of the same qualities as batteries so that they can be considered as thin film batteries that can be charged and discharged.

Mo-doping nanocrystalline WO3 electrochromic film can be prepared by spray pyrolysis. For example, some experts have prepared different concentrations of molybdenum doped nano crystalline tungsten trioxide electrochromic films by spray pyrolysis.

Tungsten trioxide powder, as an electrochromic material, can be applied to smart window, i.e., electrochromic device. Such electrochromic device is generally composed of five functional layers plated on the surface of the glass: a transparent conductive layer, a cathode discoloration layer, an electrolyte layer, an anode discoloration layer or ion storage layer and a transparent conductive layer.

Li-doped WO3 electrochromic film can be prepared by a sol-gel method. For example, some experts have prepared a Li doped tungsten trioxide electrochromic film by adding a LiCF3SO3 solution to a precursor solution using a sol-gel method.