Tungsten trioxide can be used to prepare electrochromic film and therefore be applied in the production of electrochromic device. The prepared nano film is the core of an electrochromic device with a "sandwich" structure. Tungsten trioxide nano powder is a representative of inorganic electrochromic materials, which has been studied most and has been commercialized as it has the advantages of high coloring efficiency, high chemical stability, large light modulation range and good electrochemical reversibility.

As an important functional material, tungsten trioxide has attracted much attention in research fields such as electrochromic devices, microsensors, surface acoustic wave devices, and microfluidic devices. And as an electrochromic device, tungsten trioxide has been more and more widely used in smart windows.

Hydrated tungsten trioxide can be used to prepare electrochromic film as the hydrated WO3 tends to have a two-dimensional structure that provides additional permeation channels for ion transport and a high specific surface area. In addition, it is also because the crystal water in the hydrated WO3 can accelerate the ion transport efficiency, thus improving the electrochromic performance. Therefore, not only the tungsten trioxide of hexagonal phase, but also the hydrated tungsten trioxide attracts the attention of researchers.

Hexagonal tungsten trioxide nanosheet film is a type of electrochromic film that can be prepared by hydrothermal method. In order to improve the electrochromism of tungsten trioxide, researchers usually construct a porous structural film using hexagonal phase tungsten trioxide of ions and electron conductivity, as the schematic illustration shown below.

Tungsten trioxide can be used to prepare functional film such as electrochromic films and the like. Recently, as electrochromic technology research has become hotter, the electrochromic film of tungsten trioxide nano particles has also become the focus of research. In addition, thin films of WO3 nano powder have received extensive attention in many applications such as sensors, photolysis of water, and solar cells.

Mo doped tungsten trioxide nanoparticles film is a new type of electrochromic film, which can be prepared by a spray coating method. Some experts used spray coating technology to prepare 10×10cm2 molybdenum doped tungsten trioxide electrochromic devices under laboratory conditions, and evaluated their electrochromic properties. They found that Mo doping has an effect on the response speed, cycle stability and other performance of the tungsten trioxide electrochromic film.

3D quasi-vertical WO3 nanosheet film can be prepared by electrodeposition method. First, some experts used a simple solution method to prepare a WO3∙2H2O nanosheet sol with positive charges on the surface.

Amorphous tungsten trioxide is a type of tungsten trioxide, namely ɑ-WO3, which is an electrochromic material that can be used to prepare electrochromic film.

Tungsten trioxide can be applied for the preparation of smart window as WO3 has the advantages of high electrochromic color contrast, good cycle stability and good thermal stability. And therefore tungsten trioxide nano particles have become the most researched and commercialized inorganic electrochromic material in recent years.

Tungsten oxide smart window has excellent energy saving effect. According to statistics, if such new type of smart glass is used in glass curtain wall, it can reduce the operating cost of the building by 20%, including reducing its peak demand for electricity by 24%, reducing the load on the HVAC system by 25%, and reducing the lighting cost by 60%.