Tungsten Trioxide Electrochromic Properties

In order to meet the current needs of people in different seasons and different periods of indoor lighting on the amount of light, the smart window that can dynamically adjust the solar light intensity and heat radiation has become the focus of recent research.

Tungsten trioxide is not only a n type semiconductor material, is also a kind of "d⁰" oxide, this dual identity has many characteristics, the main frame is composed of tungsten oxide tungsten oxygen eight face end to end. In the space skeleton, the pores of the tungsten oxide eight - hedron can be embedded in the smaller cations to form tungsten bronze, the reversible transformation process of tungsten oxide and tungsten bronze is always accompanied by internal electron transfer and tungsten valence change, causing discoloration reaction of light through the control and adjustment.

At present, the best electrochromic property of tungsten trioxide is blue tungsten oxide, while the colored tungsten oxide is dark blue. Since the color is relatively soft and the light-shielding property is good, it is suitable for daily home use. In addition, crystalline blue tungsten oxide also has a higher reflectivity for infrared after discoloration. Achieve similar insulation with low-e glass insulation, thereby helping to reduce indoor energy consumption.

Doping is an effective way to enhance the photoinduced properties of blue tungsten oxide. Most of the doping of blue tungsten oxide is mostly metal elements with lower electronegativity than W or weaker oxidation capacity, such as titanium, molybdenum, vanadium and cesium. The incorporation of these elements will change the crystallinity, grain size and surface contact area of the film. On the one hand, it can form a porous and large channel structure with uniform distribution and easy to transport ions on the one hand, so as to reduce the migration barrier and increase the diffusion coefficient. On the other hand, the surface roughness increases the contact area of ion conducting layer and a tungsten oxide layer, and provides a transmission channel for more ion insertion and extraction, and then improve the ion in unit time and injection volume. The tungsten oxide doped cesium is the best known properties of photochromic thermal insulating materials.

The photoluminescence of tungsten oxide can be widely used in electrochromic fields, such as intelligent window, auto rearview mirror, large area information display screen and so on. In the future, tungsten oxide based materials for smart windows will pay more attention to the near infrared band, and separate regulation of solar cells, through the effective combination of intelligent circuit of system control, building the photoelectric and photothermal conversion, and a virtuous cycle in the future is also used in a popular trend.

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