ELECTROCHROMIC OXIDES - A BAND-STRUCTURE APPROACH

This paper attempts to lay down a foundation for a comprehensive theory of electrochromism among oxides. It is pointed out that crystals of all the well known electrochromic metal (Me) oxides are composed of MeO6 octahedra in various corner-sharing and edge-sharing arrangements. In electrochromic thin films there are cluster-type and columnar microstructures based on the MeO6 units. The coordination of the ions leads to electronic bands that are able to explain the presence or absence of cathodic and anodic electrochromism in numerous defect perovskites, rutiles, and layer structures. Optical absorption can be due to intraband effects, interband transitions, and polaron hopping.