Tungsten oxide film synthesis by spray pyrolysis of peroxotungstic acid and its electrochromic characterization

摘要

Peroxotungstic acid precursor solution was sprayed on indium-doped tin oxide (ITO) glass substrates to synthesize amorphous and crystalline phase tungsten oxide thin films by changing heating temperature. We could synthesize the amorphous phase at below 400 °C and the monoclinic crystalline tungsten oxide at above 400 °C. Electrochemical and in-situ optical transmittance analysis showed that amorphous phase tungsten oxide at 250 °C had a good electrochromic property with a large optical transmittance change between its bleached and colored states. The coloration mechanisms are due to polaron generation by inserting ions and electrons to change W~(+6) state to W~(+5) or W~(+4) state.