Transition from dispersive to nondispersive transport: Photoconduction of polyvinylcarbarzole

Abstract

Photocurrents in polyvinylcarbarzole were studied over 10 decades in time. An analytical approach is proposed for extracting rate distributions from the measured photocurrents. We find that the trapping-rate distribution is not exponential but ‘‘flat’’ and that it shows a cutoff at low rates. This distribution gives rise to the novel feature of a gradual transition from dispersive to nondispersive charge transport during a single transit. The temperature and field dependence of the cutoff rate $r_c$ was studied in the framework of a Poole-Frenkel model.