Electrochromic properties of aqueous sol-gel derived vanadium oxide films with different thickness

Vanadium oxide films were spin-coated on ITO-coated glass substrates with a coating solution prepared by dissolving V2O5 powder in H2O2 solution. The cycling behaviors of the films annealed at 150°C for 1 h with different thickness were studied using cyclic voltammetry (CV) in propylene carbonate solution containing 1 mol/l LiClO4. Electrochromism of the films upon lithium intercalation was investigated by in-situ transmittance measurements during the CV process. The vanadium oxide films showed reversible multichromism (yellow↔green↔blue) upon Li+ ion insertion/extraction. Transmittance modulation range can be varied by adjusting the film thickness. Vanadium oxide films with proper thickness could be used in realization of multicolored electrochromic devices.