Electrochromism of Electrodeposited Tungsten Trioxide Films: I . Electrochemical Characterization

Electrodeposited tungsten trioxide films show fast electrochromic response both in aqueous and in nonaqueous solutions. The values of in the tungsten bronzes, , were determined by using a chronopotentiometric technique combined with UV/Vis spectroscopic analysis. The effect of double‐layer charging was discussed. A finite diffusion control model was used to analyze the insertion behavior of M + ions into the films. The apparent diffusion coefficient of Li + through the electrodeposited film is about two orders of magnitude higher than that of vacuum‐evaporated films, indicating that electrodeposited films are more suitable for use as display devices than vacuum‐evaporated films. The higher porosity of the electrodeposited films may be a main reason for the fast electrochromic response.