Organic heterostructure LEDs: numerical simulation of transport and recombination

Summary form only given. We present a numerical study of current-voltage characteristics and charge accumulation effects in multilayer organic light emitting diodes. The bipolar charge transport and recombination problem with field dependent mobilities is solved self-consistently and heterointerfaces are treated by assuming transport at discontinuities in the chemical potential to be governed by Boltzmann statistics. We show that the increased efficiency found in multilayer LEDs can be explained within the framework of our model by charge and recombination zone confinement at heterointerfaces and a resulting increase in the current balance factor. We reproduce current-voltage characteristics of single layer monopolar and bipolar polymer LEDs made of MEH-PPV by using mobility parameters previously obtained from a temperature and field dependent analysis of monopolar diodes.