Inter-chain and intra-chain hopping transport in conducting polymers

Abstract

The d.c. conductivity σdc and the a.c. electric response of poly(3-decylpyrrole) prepared with different dopants and synthesis conditions were studied over a broad temperature (75-300 K) and frequency (100 Hz-40 MHz) range, both in bulk state (films) and in solution. Concerning films, the temperature dependence of σdc followed Mott's law, with the hopping parameters strongly doping dependent. A.c. conductivity σac was strictly coupled to d.c. transport, so that a master curve resulted from a plot of normalised complex permittivity versus a critical frequency proportional to σdc. Similar results to the bulk case were observed for non-dilute solutions, whereas for very dilute solutions σdc scaled with temperature as the reciprocal of solvent viscosity. Moreover, a steeper bilogarithmic slope of σac versus frequency was found. Inter-chain charge transport in dilute solutions can be attributed to dissociated counterions diffusing through the solvent, whereas intra-chain hopping can eventually contribute only at high frequencies. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.