Prolonged lifetime of electrochromism of amorphous WO3–TiO2 thin films

Abstract

AbstractThe lifetime of the electrochromism of the WO3–TiO2 films prepared by vacuum evaporation is found to exceed that of WO3 films by a factor of five. X‐ray diffraction has revealed that the crystal structure of WO3–TiO2 films stays amorphous, while crystalline compounds are formed in amorphous WO3 films after colouring and bleaching. WO3–TiO2 films stay amorphous after they are annealed at 400°C, although WO3 films crystallize. SIMS and XPS analyses have revealed that half the amount of lithium injected during a colouring cycle is stored as OLi bonds in the bleached film. In WO3–TiO2 films the number of bonds such as WOH and WO in which lithium ions accumulate is reduced. We conclude that the lifetime of the electrochromism is prolonged for amorphous WO3–TiO2 films, because lithium does not accumulate and the WO3–TiO2 films stay amorphous.