Tungsten Trioxide/Liquid Electrolyte Electrochromic Devices with Amorphous Iron Tungstate Counter Electrodes– Response Characteristics and Cell Reliability

Abstract

Tungsten trioxide electrochromic devices using amorphous iron tungstate-graphite mixtures as counter electrodes were investigasted with the aim of attaining high reliability in such devices. The display electrode was prepared by an improved process which preserves transparent conductive layers in direct contact with the electrolyte, preventing the latter from dissolving them. Spin-on-glass-coated soda-glass substrates were used to eliminate the cell degradation caused by Na diffusion from substrate glass into WO₃ films. Iron tungstate-graphite counter electrodes typically have a large capacity of 100 mC/V·cm², with the result that the counter electrode potential change during operation was very small. Cells could be operated at a constant voltage with preferable response and long cycle lives of over 10⁷.