Solid state electrochromic device: behaviour of different salts on its performance

Optical and electrical properties of transmissive solid state electrochromi c devices based on a sandwich structure of conductive K-glass(R)(1) /WO3/po lymeric electrolyte/conductive K-glass(R), have been investigated in correl ation with the type of salt added to the polymer in order to increase its i onic conductivity. Lithium, sodium and ammonium triflate salts have been us ed with poly (ethylene glycol) ethylethermethacrylate (pPEGMA) to obtain tr ansparent and conductive semi-solid solutions. The physical properties of t he three different types of electrolytes and the operational performances e xhibited by devices in terms of colour contrast, response time and stabilit y are discussed. The colouring and bleaching mechanism and the electrochrom ic behaviour appear to be very similar in the three cases, but a rapid opti cal degradation is present for devices made up with the ammonium triflate s alt when they are operated under cyclic biasing condition. (C) 2000 Elsevie r Science BN. All rights reserved.