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.

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.

Tungsten trioxide (WO₃) is an important n-type semiconductor oxide with a variety of crystal structures. It has been extensively studied due to its unique physical and chemical properties, and has been used in electrochromism, photochromism, catalysts, and sensing materials. In order to further utilize the excellent properties of WO₃ and broaden its application fields, one technical approach is to reduce its grain size, namely nanostructured tungsten oxide.