Role of hole playing in improving performance of organic light-emitting devices with an Al2O3 layer inserted at the cathode-organic interface

The role of hole playing in improving electron injection in the presence of an Al2O3 layer at the organic-cathode interface is discussed. It is deduced that, according to the model of tunneling barrier reduction and the carrier transporting mechanism in organic light-emitting devices, electron injection will be enhanced only if holes are injected and accumulated at the organic-buffer interface. The validity of this analysis is well confirmed by experimental results. The observed abnormal characteristic of operating voltage varying with the Al2O3 layer thickness and the efficiency improvement are also well explained by the model. (c) 2006 American Institute of Physics.