An Electrochromic Window Based on Li x WO 3 / ( PEO ) 8LiClO4 / NiO

Abstract

Electrochromic materials are characterized by reversible but persistent changes of the optical properties when subjected to suitable electrochemical reactions. Electrochromism can be utilized in windows, most conveniently by exploiting all-solid-state multilayer coating backed by glass. The multilayer coating should comprise the following sequence of layers: a transparent and electrically conducting base layer, an electrochromic layer, and electrolyte, a conterelectrode, and a transparent conducting top layer. For window applications, the electrolyte should be transparent, and the conterelectrode must be either optically passive (colorless irrespective of its ionic content) or electrochromic in a sense that is complementary to the electrochromism of the electrochromic layer. The latter condition implies that if the electrochromic layer is cathodic (anodic), the counterelectrode must be anodic (cathodic). This paper reports preliminary data taken on samples with electrochromic layers based on tungsten oxide, WO{sub 3}, and nickel oxide, NiO, and an intermediate solid electrolyte of poly(ethylene oxide) doped with lithium perchlorate, (PEO){sub 8}LiClO{sub 4}, where 8 signifies the number of oxygen heteroatoms per lithium ion.