Testing and control issues in large area electrochromic films and devices

It is well known that the switching time for a large electrochromic window is much longer than for a small window. The dependence of switching time with size is not linear. This work is concerned with the switching characteristics of a large device. This issue is addressed from three perspectives: considering the equivalent circuit of an electrochromic device; the arrangement of the external connections and optimization of switching procedure. A one dimensional device model and a one dimensional electrode setup is considered in the Micro Cap V lumped element circuit analysis. The analysis is performed using passive resistors and voltage dependent capacitors. Simulations of transient response to voltage and current are presented, and the implications of the results for coloration kinetics of large devices are discussed. Initial recommendations on device design and optimum switching procedure are presented. (C) 1999 Elsevier Science Ltd. All rights reserved.