Tungsten trioxide, or WO3, together with MoO3, TiO2, Nb2O5, is a typical representative of a cathode electrochromic material, i.e., cathode coloring material, which is more and more widely used in smart windows. So, what is a cathode coloring material?

Tungsten trioxide is a representative inorganic electrochromic material, which has also become the most researched inorganic electrochromic material. WO3 realized commercialization due to its high coloring efficiency, large light modulation range, good electrochemical reversibility and high chemical stability.

Mo doped WO3 nanowires film can be prepared by nanowire spraying. Experts amplified the preparation technology of this porous electrochromic film under laboratory conditions to prepare an electrochromic device of size of 10×10cm2. Experts also said that such spraying technology is expected to replace the vacuum coating process in the future, reducing the production cost of large-area electrochromic devices.

Nest-like WO3•0.33H2O film can be prepared by self-seeded hydrothermal method on an FTO conductive substrate. So, what are the advantages of using the self-seeded hydrothermal method to prepare tungsten trioxide electrochromic film?

WO3•0.33H2O nanosheet film can be prepared by seed-assisted hydrothermal method on FTO (SnO2: F) conductive glass. Expert found that:

Mo doped WO3 nanoparticles film can be prepared by a nanoparticle spraying method. The Mo doped tungsten trioxide electrochromic film has a light modulation range of 43%. The coloring time and response time are 10 and 7 seconds, respectively.

3D quasi-vertical WO3•0.33H2O nanosheet film can be prepared by electrodeposition method, that is, the hydrated tungsten trioxide nanosheet prepared by a simple green solution method is formed on the conductive substrate, which can solve the limitation of the hydrothermal method on the film substrate.

The discoloration mechanism of the crystalline tungsten oxide thin film conforms to the Drude-like free electron scattering model. And the free electrons play an important role in the optical properties of the electrochromic performance of the crystalline tungsten oxide film.

Crystalline tungsten oxide film can be prepared by a reactive magnetron sputtering method under different oxygen partial pressures. The experts analyzed the surface morphology and the density of the WO3 thin films under different oxygen partial pressures, and studied the effects of surface morphology and porosity on the electrochromic properties.

Ti-doped yellow tungsten oxide thin film has the same electrochromic properties as the tungsten trioxide thin film. Experts say that at present, the research on the electrochromic properties of Ti-doped tungsten trioxide film is mostly concentrated in chemical preparation methods, such as sol-gel method and hydrothermal method. And there are few reports on the preparation of Ti-doped WO3 thin film by reactive magnetron sputtering method.