Electrochromism refers to the reversible change in light transmittance and/or reflectance associated with an electrochemical redox reaction after the material is applied with an appropriate voltage. Applications of electrochromic devices include: smart windows for cars and buildings, controllable light reflection or light transmissive display devices (for optical information and storage), controllable aircraft canopies, reusable price tags, spacecraft Thermal control and more.

Tungsten bronze has photochromic properties and can be applied to building windows films and automotive insulation films (smart glass). However, there are currently few studies on this.

The tungsten trioxide film can be colored by irradiation of light of an appropriate energy. When the tungsten trioxide film is irradiated by light, electrons e- and electron holes h+ are generated, and photogenerated electrons enter the conduction band of the tungsten trioxide. The photo-generated electron holes react with the adsorbed water on the surface of the film to form H+, and then diffuse to the center of tungsten trioxide, thus leads to a difficulty in color change.

Tungsten trioxide is an inorganic electrochromic material with excellent electrochromic properties. Electrochromism refers to the phenomenon that the optical properties of a material undergo a reversible change under the action of an applied electric field, and the appearance is a reversible change in color and transparency.