Bibliography; and ‘electrochromism’

Brief histories of electrochromism have been delineated by Chang (in 1976), Faughnan and Crandall (in 1980), Byker (in 1994) and Granqvist (in 1995). Other published histories rely very heavily on these sources. The additional histories of Agnihotry and Chandra (in 1994) and Granqvist et al. (in 1998) chronicle further advances in making electrochromic devices for windows. The first books on electrochromism were those of Granqvist, and Monk, Mortimer and Rosseinsky, which were both published in 1995.

Platt coined the term ‘electrochromism’ in 1961 to indicate a colour generated via a molecular Stark effect (see page 4) in which orbital energies are shifted by an electric field. His work follows earlier studies by Franz and Keldysh in 1958, who applied huge electric fields to a film of solid oxide causing spectral bands to shift. These effects are not the main content of this book.

Early redox-coloration chemistry

In fact, redox generation of colour is not new – twentieth-century redox titration indicators come to the chemist's mind (‘redox’, Section 1.1, implying electron transfer). However, as early as 1815 Berzelius showed that pure WO3 (which is pale yellow) changed colour on reduction when warmed under a flow of dry hydrogen gas, and in 1824, Wöhler effected a similar chemical reduction with sodium metal. Section 1.4 and Eq. (1.5), and Eq. (2.5) below, indicate the extensive role of WO3 in electrochromism, amplified further in Section 6.2.1.