Transient Photocurrents in Pyrene-TCNE Single Crystals. I. Currents Controlled by Surface Layers

Abstract

Transient hole-photocurrents were measured in the direction perpendicular to bc-plane of a pyrene-TCNE single crystal. In order to interpret behaviours of photoresponses to the applied voltage and the series resistance, a model, that the crystal has surface layers, where the density of carrier trapping- or recombination-centers is higher than that in a bulk, was proposed.
This model explained satisfactorily the experimental results. Life times in the bulk, that in the surface layer and mobility of carriers were estimated to be about 10⁻⁶ sec, 10⁻⁷ sec and 10⁻² cm² V⁻¹ sec⁻¹ respectively.