Simulation of charge injection enhancements in organic light-emitting diodes

We have investigated by numerical simulation of real devices the reasons for electron injection enhancement due to lithium fluoride (LiF) and for hole injection enhancement due to copper phtalocyanine (CuPc) in organic light-emitting diodes (OLEDs). The reference data introduced in the code were obtained from Kelvin probe and charge transport measurements. In the case of LiF, the reduction of the injection barrier is mainly due to a static dipolar charge distribution across the ionic layer, while in CuPc the space charge which lowers the barrier results from a large hole accumulation at the CuPc/hole-transmitting layer interface, during injection.