WO3, or tungsten trioxide, is a cathode coloring material with a relatively low color contrast so that it needs to be assembled into a composite electrode complementary electrochromic device together with an anode coloring material such as nickel oxide. Wherein the tungsten oxide film acts as an electrochromic layer. And nickel oxide, as the anode coloring material preferred by researchers, can be used not only as an electrochromic layer, but as an ion storage layer of, to further enhance the light modulation range of the device.

Yellow tungsten oxide, or tungsten trioxide, is a cathode discoloration material. The color contrast of tungsten trioxide is still relatively low compared to a composite electrode complementary electrochromic device assembled using WO3 and nickel oxide. Wherein nickel oxide is the anode coloring material preferred by researchers, which includes nickel oxide of ideal ratio (light green) and nickel oxide of non-ideal ratio (gray black).

Tungsten trioxide is a cathode coloring material that can be assembled with an anode coloring material such as nickel oxide into a composite electrode complementary electrochromic device. In contrast to WO3, nickel oxide is such a type of material that carry out oxidization firstly and then discoloration. Nickel oxide can be used as a counter electrode to form a device together with a cathode coloring material such as tungsten oxide, thereby achieving the effect of storing ions and increasing the range of light modulation.

Tungsten oxide for producing composite electrode complementary electrochromic device is a typical cathode coloring material. However, in practical applications, the coloring contrast of tungsten oxide is still relatively low. How to solve this problem? In this regard, experts say that if an anode coloring material and a cathode coloring material are assembled into a complementary electrochromic device, the coloring contrast can be greatly improved.

WO3 for preparing large area electrochromic device is in an amorphous state (a-WO3) at 300 °C and in a crystalline state (c-WO3) at 400 °C and 500 °C. Experts say that the amorphous tungsten trioxide film has higher coloring efficiency and shorter response time than the crystalline tungsten trioxide film. It means that a-WO3 film has better electrochromic performance than c-WO3 film.

Yellow tungsten oxide, as an inorganic electrochromic material, is one of the key factors for the successful commercial application of large area electrochromic device. So, tungsten trioxide has received more and more attention from building field. In addition to electrochromic materials, polymer electrolyte is also a key to the successful commercial use of electrochromic devices.

Tungsten trioxide is assembled in a large area electrochromic device in the form of an electrochromic thin film to serve as a cathode coloring material. Experts said that for large-area electrochromic devices assembled with WO3 electrochromic film, in practical use, the cycle stability should also be taken into account in addition to factors such as light modulation range, coloring efficiency and response time.

Large area electrochromic device, with high thermal insulation and high heat preservation performance, is one of the main means to improve the energy-saving efficiency of buildings, wherein tungsten oxide is assembled in the form of an electrochromic film, playing the role of an electrochromic layer. While at present, large-area electrochromic devices have not been promoted. But why?

Tungsten oxide film may be applied for preparing an energy saving film. According to experts, the electrochromic phenomenon of such a tungsten trioxide electrochromic film for thermal insulating and energy-saving glass, that is, the conversion phenomenon between the colored state and the bleached state, can be explained by a double injection model.

What effect does the tungsten oxide electrochromic film for producing thermal insulating window glass have on the cycle stability of electrochromic devices? Through the XPS analysis of tungsten trioxide electrochromic thin film, the experts reached the following conclusions: