Infrared switching electroemissive devices based on highly conducting polymers

The use of highly conducting polyaniline films as active layers in electroc hromic devices operating in the mid-infrared, IR, range (8-12 mu m) has bee n investigated. Upon reversible electrochemical doping, the specular reflec tance of thin films deposited on an IR transparent window and electrode swi tches from 0.2 to 0.65 around 12 mu m. The complex refractive index of the conducting polymer has been determined by ellipsometry in the range 0.3 to 16 mu m. Optical calculations of the multilayer structure demonstrate that the active layer thickness to maximum contrast should be close to 300 nm. D evices incorporating a lithium or protonic gel ionic conductor and WO3 as i on storage layer have been built. Optical performance in the infrared is si milar to that of the layer in contact with a liquid electrolyte. The respon se time (t(90)) determined from optical density changes at 633 nm is of a f ew seconds. Moreover, devices incorporating the Li+ conductor retained 81% of the original reflectance contrast after 900 cycles. (C) 1999 Elsevier Sc ience S.A. All rights reserved.