Charge–discharge kinetics of electric-paint displays

The charge–discharge kinetics of electrochromic displays, based on porous nanostructured viologen-derivatized TiO 2 films, were investigated by standard electrochemical techniques. Various display compositions and geometries were studied. Chronocoulometry data were analyzed in terms of a simple approximate model for the display charging in optical switches. It was found that the charging speed of “standard displays” is limited mainly by the electrical resistance in the transparent conducting substrates and the capacitance due to the electrochemically 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 decomposed in contributions from the porous films and the transparent conductive substrates.