A semi-empirical model for the charging and discharging of electric-paint displays

Electrochromic displays based on porous nanostructured films, "electric-paint displays", are promising for electronic-paper applications due to their prominent paint-on-paper qualities. We have investigated the charge-discharge kinetics of electric-paint displays by chronocoulometry experiments. Whereas the charging curves are exponential, A(1 - e(-t)/tau), up to about 1 s, the discharging (when bleaching the display) cannot be described properly by a single exponential expression in the 0-1 s time regime. A semi-empirical model, in which the display is treated like a serial RC-circuit with a capacity step function, was developed and fitted to the experimental chronocoulometry curves with successful results. The general features of both the charging and discharging curves, as well as their dependences on the applied voltage, are reproduced in the 0-1 s regime by the suggested model. (C) 2002 Elsevier Science B.V. All rights reserved.