Forward biasing of transparent nanocryst. TiO2 (anatase) films in lithium ion-contg. org. electrolytes leads to rapid and reversible coloration due to electron accumulation and Li+ intercalation in the anatase lattice. Absorption of >90% light throughout the visible and near IR can be switched on an off with a few seconds. The nanocryst. morphol. of the film plays role in enhancing the electrochromic process.