Yellow tungsten oxide powder, also known as tungsten trioxide powder, can be first prepared into a WO3 film and used to produce an electrochromic device. Wherein, for the electrochromic mechanism of the WO3 electrochromic film, Deb was explained by a color center model. He believed that the discoloration mechanism is:
More details, please visit:
http://www.tungsten-powder.com/tungsten-oxide.html
In the process of vacuum evaporation to form an amorphous film, tungsten trioxide forms a large number of defects of positively charged structure (similar to F core) due to the loss of oxygen ion volatilization. These defects are likely to be oxygen ion vacancies. When electrons injected from the cathode enter the WO3 film, they are locally formed in these oxygen vacancies, forming F or F+ center, but these trapped electrons are unstable. They readily absorb visible photons and are excited to the conduction band, making the WO3 film showing a color. At the same time, the water in the a-WO3 film is decomposed into H+ and OH- by the electric field, and the protons migrate toward the cathode to compensate for the injected electrons, maintaining electrical neutrality.
