ELECTROCHROMISM OF ELECTRODEPOSITED TUNGSTEN TRIOXIDE FILMS .1. ELECTROCHEMICAL CHARACTERIZATION

Electrodeposited tungsten trioxide films show fast electrochromic resp onse both in aqueous and in nonaqueous solutions. The values of x in t he tungsten bronzes, MxWO3, were determined by using a chronopotentiom etric technique combined with UV/Vis spectroscopic analysis. The effec t of double-layer charging was discussed. A finite diffusion control m odel was used to analyze the insertion behavior of M+ ions into the fi lms. The apparent diffusion coefficient of Li+ through the electrodepo sited WO3 film is about two orders of magnitude higher than that of va cuum-evaporated WO3 films, indicating that electrodeposited films are more suitable for use as display devices than vacuum-evaporated films. The higher porosity of the electrodeposited WO3 films may be a main r eason for the fast electrochromic response.