Electrochromic properties of doped tungsten oxide electrochromic thin film are affected by the stability of the tungstic acid sol during the preparation process. Therefore, in order to improve the stability of the sol or to control the proper viscosity and film forming properties, experts have studied the effect of the addition of PEO on the tungstic acid sol. The figure below shows the viscosity curve of a member with the adding of PEO, that is, the effect of the amount of PEO added on the stability of a certain component sol. The composition of the sol is: WO3 is 0.0962mol; MoO3 is 0.0289mol; C2H5OH is 50mL; and isopropanol is 30mL.

Electrochromism can be referred to a phenomenon in which the reflectance, transmittance and absorptivity of doped WO3 film undergo a stable and reversible color change under the action of an applied electric field. Experts say that the electrochromic properties of tungsten trioxide will be effectively improved when the doping content is within a certain range.

Doped WO3 electrochromic thin film can be prepared by the following steps: preparation of a stable sol and preparation of a WO3 film by using the stable sol which has been subjected to aging treatment as a precursor liquid.

Electrochromism can be referred to the phenomenon that the optical properties of a doped tungsten oxide film undergo a stable and reversible color change under the action of an applied electric field, and its appearance is a reversible change in color and transparency. Wherein, the doped WO3 film is a kind of an inorganic oxide film that can causes electrochromic phenomenon.