Tungsten trioxide film can be used to assemble an all-solid-state smart window, in which WO3 film acts as an electrochromic layer. Some experts have studied the optical property of WO3 electrochromic film. The transmission spectrum of the all-solid-state electrochromic window in the colored state and the bleached state is shown in the figure below. Wherein, the working voltage is ±3.5V.
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Experts said that it can be seen from the figure that the smart window has a certain ability to adjust the visible light transmittance, but the transmittance in the bleached state is low as the transmittance of the last layer of ITO film is not high. Since the ITO film is deposited by DC magnetron sputtering using an InSn alloy target, to obtain high transmittance and electrical conductivity, the deposited ITO film is usually subjected to high-temperature heat treatment. However, the electrochromic properties of WO3 and NiO films are impaired after high temperature heat treatment. Therefore, in the preparation of the all solid state smart window device, the last ITO film was not heat treated. In addition, at present, some experts have mastered the technology of using ITO ceramic targets without annealing to prepare ITO films. Therefore, by adopting this new technology for preparing ITO films, it is expected to produce all-solid-state smart window devices with better performance.
