Peroxotungstic Acid Coated Films for Electrochromic Display Devices

Abstract

Peroxotungstic acid coated films were investigated for applications to electrochromic display devices. Films coated with peroxotungstic acid aqueous solutions exhibited electrochromism in non-aqueous electrolyte solutions containing Li-salts. A good reversibility for the electrochromic reaction was attained after several writing-erasing cycles involving linear sweeps when the films had been heat-treated at about 120°C for 1 h. Cathodic polarization of the coated films irreversibly reduced the peroxotungstic acid to tungsten trioxide in the electrolyte. This resulted in the devices having poor initial response characteristics. After several aging cycles, however, the coloring efficiency and response rate of the coated films were favorable and comparable to those of tungsten trioxide evaporated films.