INTERPRETATION OF SURFACE-POTENTIAL KINETICS IN POLY(N-VINYLCARBAZOLE) BY A MODEL OF TRAP-CONTROLLED HOPPING TRANSPORT

We report room temperature measurements of the surface potential dark decay in amorphous poly(N-vinylcarbazole) films over the field strength range 0.6-2.6 x 10(8) V m-1. A model of trap-controlled hopping is used to describe the experimental curves. The decay curves are influenced, not only by shallow, but also by deep traps. The model parameters such as the effective hole mobility (congruent-to 10(-16) m2 V-1 s-1 corresponding to the mobility of charge carriers controlled by shallow traps deeper than 0.55 eV), the hopping distance (congruent-to 0.6 nm) and the capture and release rates of charge carriers in a deep hole trap were determined by curve fitting. The effective hole mobility as well as the trapping time were found to be weak functions of field strength. The depth of the deep trap was estimated to be 0.9 eV.