Optical constants of electrochromic films and contrast ratio of reflective electrochromic devices.

This study investigates the optical constants of WO3 electrochromic films and NiO ion-storage films in bleached and colored states and that of a Ta2O5 film used as an ion conductor. These thin films were all prepared by electron-beam evaporation and characterized using a spectroscopic ellipsometer. The spectra obtained using a spectrophotometer and those calculated from the optical constants agreed closely. An all-solid thin-film reflective electrochromic device was fabricated and discussed. Its mean contrast ratio of reflectance in the range of 400-700 nm was 37.91.