High coloration efficiency electrochromics and their application to multi-color devices

Electrochromic materials could be used to make very rapid, efficient displays and light modulators if they can be developed with sufficiently high coloration efficiency. Electrochemically active conjugated polymers such as poly(3,4-ethylenedioxythiophene-didodecyloxybenzene) (PEB) are identified that display unusually high coloration efficiencies in narrow wavelength ranges. Since WO, is a low coloration efficiency material in comparison, it can be used as a counter electrode in charge-balanced variable transmittance cells with FEB. A maximum coloration efficiency of similar to 1250 cm(2) C-1 at 552 nm is reported for a PEB-WO3 device. A conductive polymer with complementary colors to PEB, poly(3,6-bis(2-(3,4-ethylenedioxy)-thienyl)-N-eicosylcarbazole) (PBEDOT-Cz(C20H41)), was also assembled into a variable transmittance cell. The two cells in series and independently controlled were shown to cover a two-dimensional surface in color space. (C) 2001 Elsevier Science Ltd. All rights reserved.