The coloration of tungsten-oxide film by oxygen deficiency and its mechanism

The transmissivity and the optical absorption of a WO3 film with oxygen deficiencies introduced were characterized and compared with those of an electrochromically colored WO3 upon injecting a proton (H+). The WO3 film with oxygen deficiencies introduced was clearly colored blue. It was shown that the wavelength regions of optical absorption of both films almost overlapped each other.