Evolution of Polaron States Into Bipolarons In Polypyrrole

Abstract

The kinetics of polaron recombination into bipolarons in polypyrroie have been studied using optical absorption spectroscopy on films doped in situ in an electrochemical cell. ESR studies confirm that the metastable states possess spin, while the stable states do not. We also report the development of a new electrochemical technique which indicates charge is stored at two localized energy levels in the gap. The optical and ESR data both reveal a slow evolution, consistent with polaron diffusion rates limited by the mobility of the accompanying counterion.