Hole mobility on isolated chains of poly(3-hexylthiophene) by microwave conductivity measurement

We demonstrate a facile method to investigate intrinsic charge mobility on isolated chains of conjugated polymers by use of microwave absorption method. Hole carriers are generated on conjugated polymer chains in dilute solution by doping with the p-type dopants NOSbF(6), instead of using excitation sources of pulsed laser and electron beam as reported in the literature. The number of hole carriers can be easily estimated by doping level. Measurements on poly(3-hexylthiophene) in benzene with various doping levels from 0.1% to 3% indicate that the hole mobility can be divided into two ranges. In the doping level 0.1%-0.3%, the hole mobility maintains at the constant level 0.03 cm(2)/V s, which can be regarded as that on an isolated chain since the average number of hole carriers per chain is only around one. As the doping level is higher than 0.3%, a presence of multiple hole carriers on a chain occurs, which results in a repulsion of hole carriers and leads to a reduced hole mobility.