Mechanism of electrochromism in WO3

Abstract

X‐ray photoelectron spectra of colored WO₃ films, thermodynamic analysis of galvanic behavior of the tungstic oxide cathode, plus other new lines of evidence, clearly establish the previously uncertain mechanism of the electro‐optic effect in amorphous WO₃, viz., a simultaneous injection of electrons and positive ions into a film via an electrochemical process, with the consequent development of a low‐x tungsten bronze. The positive ion, in both the films and in tungsten bronzes, remains fully ionized even in the presence of high densities of injected electrons.