ELECTROCHROMIC DISPLAY DEVICES OF TUNGSTIC OXIDE CONTAINING VANADIUM-OXIDE OR CADMIUM-SULFIDE AS A LIGHT-SENSITIVE LAYER

Solid-state electrochromic display devices (ECDs) have been prepared u sing vacuum deposited tungstic oxide as the primary electrochromic mat erial. Such devices form colour during irradiation from a fluorescent- tube as light source. Initial experiments incorporated (evaporated) Cd S films and the proton-conducting poly(ethylene oxide)-phosphoric acid electrolyte (1:1) plasticised with acetonitrile. Successful photoelec trochromic devices were prepared in this way provided the electrolyte was anhydrous, since films of CdS are sensitive to water-attack. Anoth er device to evince photoelectrochromism was one containing layers of WO3 and V2O5. This combination of oxides was the most promising respon ding to a 1/20s flash of intense white light. As yet, the colour forme d in this way cannot be electro-bleached. These displays may also be u sed as normal-electrolytically driven-devices in the absence of irradi ation.