Large-scale electrochromic devices for smart windows and absorbers

Abstract

Application of smart windows and absorbers demand electrochromic (EC) devices with long term stability and a large scale production technology. The paper presents recent results on preparation of rigid and flexible EC devices with 0.3 X 0.3 m 2 active area in a three layer arrangement (polyaniline/polymeric electrolyte/tungsten trioxide). The main items and risks of processing an EC element are discussed. It is shown, that highly conductive, chemical resistant electrodes (sheet resistance 5 (Omega) /sq., transparency 85%) on flexible PMMA and PC substrates can be prepared by low temperature sputtering of indium tin oxide (ITO). Deposition apparatus and parameters are described. Well known standard techniques for the synthesis of EC films like polyaniline and tungsten trioxide are adapted for large surfaces: polyaniline and tungsten trioxide based EC films on ITO glass have been prepared with chemical and electrochemical preparation techniques. Electrode geometry plays an important role for the homogeneity of the grown film. We succeed in minimizing tolerances in optical density over 0.3 X 0.3 m 2 down to 2%. The solid polymer electrolyte essentially determines the performance of the EC device. High transmittance, proper conductivity, and strong adhesion, are the main attributes.