The electrochromic film of Ta doped tungsten trioxide nanoparticles has an amorphous structure, just like tungsten trioxide electrochromic film. Experts said that the tungsten trioxide film deposited at room temperature is an amorphous electrochromic film with a smooth surface, uniform texture and porosity.
When the amount of Ta doping is within a certain range, the surface of the film is smooth and uniform. As the doping amount of Ta increases, larger particles begin to be embedded inside the film. These particles are denser, which destroys the porosity and uniformity of the film. When the Ta doping amount reached 35%, even micron-sized particles appeared on the surface of the film.
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In addition, experts also said that the doped tungsten oxide film after coloring does not absorb blue light, so the color of the film appears blue, which is the electrochromic effect of WO3 film from transparent to blue. On the other hand, the doped tungsten oxide film has a higher absorption of the red to green light band, which is advantageous for the energy application of the WO3 film. Because the light near the red light is the main source of thermal energy, the absorption of this spectrum is beneficial to the application of smart windows.
