Charge carrier transport and recombination at the interface between disordered organic dielectrics

An analytic model of charge carrier hopping at the interface separating two disordered organic materials in organic light-emitting diodes (OLEDs) is formulated. It is shown that the rate of charge carrier injection across such an interface is much lower than the rate of first interfacial jumps, most of which are followed by return carrier jumps back into initially occupied sites. In OLEDs, the rate of injection across the interface determines the leakage current while the rate of radiative recombination is proportional to the first-jump rate. Therefore, the marked difference between the injection rate and the rate of first carrier jumps across the interface implies a much higher efficiency of carrier recombination at the interface than predicted by the conventional Langevin theory of recombination. (C) 2001 American Institute of Physics.