Efficiency and humidity dependence of WO3-insulator electrochromic display structures

Abstract

Contrast ratio, optical density, efficiencies, coloration, and bleaching times of WO₃‐insulator (LiF, MgF₂) sandwich display structures have been measured and are compared to the characteristics of WO₃‐liquid electrochromic cells. The efficiencies of the two are comparable, but it is harder to achieve sufficient contrast in the solid‐state structures. Measurements in a controlled‐humidity environment demonstrate clearly the crucial role of the presence of water vapor in the operation of these sandwich structures. Transport of protons through the insulator is indicated as the rate‐limiting mechanism.