Yellow tungsten oxide, which is also referred to as tungsten trioxide or WO3, has excellent electrochromic property. It is excellent electrochromic property that makes yellow tungsten oxide become a typical cathode electrochromic material. And the amorphous WO3 film is considered to be one of the most promising electrochromic materials. And therefore, WO3 is often seen in researches on electrochromic devices such as smart windows.
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That is because the amorphous WO3 film has the advantages of high coloring efficiency, good reversibility, short response time, long life, low cost, wide optical change range during coloring and fading, etc.
The electrochromic process of yellow tungsten oxide film: when electrons and ions are injected into the transparent WO3 film, the film turns blue, and when the ions and electrons are extracted, the film changes back to its original state - transparent. This is due to the reduction of part of W6+ to W5+ to produce tungsten bronze - MxWO3.
