Mobilities of charge carriers hopping between π-conjugated polymer chains

Abstract

Mobilities of charge carriers in a copolymer film where a possible charge transport is restricted to an interchain path are measured by electrochemical means with doping level as a parameter. The mobility in the low doping regime, corresponding to that of polarons, is 10−6 cm2 V−1 s−1, comparable with polaron mobilities in polythiophene films where hopping transports via interchain and intrachain routes are both feasible. The coincidence suggests strongly a potential role of the interchain hopping transport in the conduction mechanism of common conducting polymers. As the doping level increases, the mobility falls down to 0.4 × 10−6 cm2 V−1 s−1 and then rises up to 6 × 10−6 cm2 V−1 s−1. Based on spectroelectrochemical measurements of the copolymer film, the decrease of the mobility is interpreted in terms of the generation of cation radical π-dimers that are inactive in charge transport. The mobility increase in a high doping region is ascribed to some structural change of a polymer network, leading to enhancement of the interchain hopping probability.