Charge-discharge kinetics of electric-paint displays

The charge-discharge kinetics of electrochromic displays, based on porous nanostructured viologen-derivatized TiO2 films, were investigated by std. electrochem. techniques. Various display compns. and geometries were studied. Chronocoulometry data were analyzed in terms of a simple approx. model for the display charging in optical switches. It was found that the charging speed of "std. displays" is limited mainly by the elec. resistance in the transparent conducting substrates and the capacitance due to the electrochem. active porous films. Support for the assumed voltage-dependence of the display resistance and capacitance in the charging model comes from cyclic voltammetry and impedance spectroscopy measurements. Based on observations of rapid current pulses following voltage steps, a modified charging model is suggested. In this model, the display capacitance is decompd. in contributions from the porous films and the transparent conductive substrates.