Lifetime of Electrochromism of Amorphous  WO 3 ‐ TiO2 Thin Films

The degradation of the electrochromism of amorphous and films prepared by electron‐beam deposition have been studied. The lifetime of the films is five times longer than that of the films. SIMS and XPS analyses have revealed that lithium accumulates as OLi in the films, but that it cannot accumulate in the film. O1s electron energy loss spectroscopy (EELS) spectra have indicated that the change of the electronic structure for the film by coloration is smaller than that for the film. The increase of plasmon energy has been obtained in low loss EELS spectrum and the increase of the bond length in the film has been measured by Raman spectrum. From these results, the number of the defect bonds as a trapping site of lithium is reduced and the bond length of W‐O decreases in the films. We conclude that lithium cannot accumulate in the structure of the film and that the structure gives a prolonged lifetime to the electrochromism.