Dopant-induced crossover from 1D to 3D charge transport in conjugated polymers

The interplay between inter- and intrachain charge transport in bulk polyth iophene in the hopping regime has been clarified by studying the conductivi ty sigma as a function of frequency w/2 pi (up to 3 THz), temperature T, an d doping level c. We present a model which quantitatively explains the obse rved crossover from quasi-one-dimensional transport to three-dimensional ho pping conduction with increasing doping level. At high frequencies the cond uctivity is dominated by charge transport on one-dimensional conducting cha ins.