Nanostructured metal oxides for printed electrochromic displays

Electrochromic devices are able to change their optical properties reversibly under the action of applied voltages. The conventional method of fabricating electrochromic devices utilizes a 'sandwich' configuration of electrodes. We developed a `side-by-side' design for fabricating electrochromic display devices without the use of conductive, transparent electrodes. A simple printing technology can be used to produce commercial scale, flexible electrochromic displays. We have also discovered that tin oxide nanocrystallites heavily doped with antimony exhibit a high level of electrochromism. The high contrast ratio of nanostructured antimony-tin oxide (ATO) electrochromic displays is attributed to an accessible antimony energy state in the band gap of the mixed oxide. The fast switching rate can be attributed to the high surface area of, and high number density of grain boundaries in, the nanophase ATO materials. The interfacial regions between ATO nanocrystallites facilitate the transport of ions in and out of the electrochromic layer. The dynamics of the electrochromic displays is critically dependent on the nanostructure of the electrochromic layer. The design strategy for commercial production of printed, flexible electrochromic displays will be discussed. (C) 2000 Elsevier Science S.A. All rights reserved.