Basic Electrochromics of CPs

Abstract

Electrochromism, i.e. change of color or spectral signature with applied voltage (or equilibrium potential or chemical potential), is one of the most prominent and fundamental properties of CPs. It is one of those which aroused the most interest for practical applications initially. CPs possess the unique property that their color changes with redox state,which in turn is nearly always related to doping level of the CP. This doping level is altered in varied ways: electrochemically, by applying a suitable potential to the polymer; chemically, subjecting the CP to chemical oxidation or reduction, and usually involving a dopant ion; and by secondary, indirect chemical means, such as alteration of the pH, which again affects the redox state of the polymer. Doping can, it must be remembered, be oxidative (‘p-type’, with the CP undergoing oxidation and the dopant being an anion) or reductive (‘n-type“, CP undergoing reduction, dopant cation), with the former far more common.