Nanostructured metal oxides for printed electrochromic displays

Electrochromic devices are able to change their optical properties reversib ly under the action of applied voltages. The conventional method of fabrica ting electrochromic devices utilizes a 'sandwich' configuration of electrod es. We developed a `side-by-side' design for fabricating electrochromic dis play devices without the use of conductive, transparent electrodes. A simpl e printing technology can be used to produce commercial scale, flexible ele ctrochromic displays. We have also discovered that tin oxide nanocrystallit es heavily doped with antimony exhibit a high level of electrochromism. The high contrast ratio of nanostructured antimony-tin oxide (ATO) electrochro mic displays is attributed to an accessible antimony energy state in the ba nd 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 nanocrystallit es 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 commerc ial production of printed, flexible electrochromic displays will be discuss ed. (C) 2000 Elsevier Science S.A. All rights reserved.