Spectroscopic Characterization of the Mixed Film TiO2-V2O5, Used as Counter Electrode in Electrochromic Devices and in Liquid Crystal Cells'

Mixed systems TiO2-V2O5 are promising candidates for the improvement of counterelectrodes in electrochromic cells. In principle, they must give a good compromise between the performances of the separate components, in terms of transparency, chemical stability and charge capacity. The sol-gel method assures a better homogeneity of the starting precursors, thus a greater stability of the deposited films. The chemical and structural homogeneity of these films has been analysed by using a micro-Raman mapping, on as grown samples, as well as on samples undergoing annealing at increasing temperatures. We have indications that most of the samples are in amorphous state, with the remarkable occurrence of polyvanadate chains, even after annealing at 400 °C but a separate crystallization can be observed for some point, and an inhomogeneous distribution, consisting of stripes of amorphous material is observed, for samples grown under specific pH condition during the sol-gel route.