<title>Electrochromic switching with nanocrystalline TiO<formula><inf><roman>2</roman></inf></formula> semiconductor films</title>

Forward biasing of transparent nanocrystalline TiO<SUB>2</SUB> (anatase) films in lithium ion containing organic electrolytes leads to rapid and reversible coloration due to electron accumulation and Li<SUP>+</SUP> intercalation in the anantase lattice. Absorption of > 90 percent light throughout the visible and near IR can be switched on and off within a few seconds. The nanocrystalline morphology of the film plays a primordial role in enhancing the electrochromic process. Preliminary results from the reduction of a surface attached viologen molecule leading to a blue coloration of the film are reported.