Charge transport and electric field-dependent exciton dissociation in organic semiconductors measured using accumulation at an insulator–semiconductor layer

Abstract

Knowledge of charge transport and exciton behavior in organic semiconductor materials is essential to develop high-performance devices. Experimental methods based on the photogeneration of charges offer the opportunity to probe both exciton dissociation and the subsequent charge transport in the same device under the same conditions. In this work, we study the common organic light-emitting diode material tris(2-phenylpyridine)iridium(III), Ir(ppy)3, and show that the yield of free charge carriers from photogenerated excitons is strongly dependent on the electric field in the semiconductor. We simultaneously measure the hole mobility in this material. Our experiments are based on the accumulation of charge carriers at a semiconductor–insulator interface, and we find that the dynamics of this charging process provide information about exciton dissociation and charge carrier mobility. This work illustrates the importance of considering the electric field dependence of exciton dissociation when interpreting charge transport experiments.