Cs doped tungsten oxide may be applied for producing near infrared shielding material. And the prepared material not only possesses photochromic property (photochromism), but also has electrochromic property (electrochromism). Then, what do photochromism and electrochromism mean?
Photochromism refers to the tendency of the obtained cesium doped tungsten oxide heat-insulating material to exhibit good shielding performance to ultraviolet and near-infrared in the ultraviolet region and the short-wave near-infrared region. And the near-infrared shielding trend is deepened after ultraviolet irradiation. Moreover, after the irradiation of ultraviolet light, the color is deepened, indicating that photochromism has occurred.
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Electrochromism is the change in some optical properties of cesium doped tungsten oxide thermal-insulation material under the action of an electric field. And such changes are reversible, such as transparency (colorless) and apparent color of the material (blue). The color center model can be used to explain electrochromism. The lattice defects of holes and electrons are trapped, forming a color center that absorbs light of a specific wavelength. In other words, the lattice defects generated by the Cs doped tungsten oxide powder under the action of an electric field combine with free electrons to form a color center, exhibiting electrochromic property.
