Fabrication and electroluminescence of double-layered organic light-emitting diodes with the Al2O3/Al cathode

The effects of a controlled Al2O3 buffer layer on the behavior of highly efficient vacuum evaporated aqua-regia-treated indium tin oxide (ITO)/triphenyl diamine (TPD)/8-tris-hydroxyquino-line aluminum Alq(3)/Al2O3/Al light-emitting diodes are described. It is found that, with a buffer layer of suitable thickness, both current injection and electroluminescence output are significantly enhanced. The enhancement is believed to be due to increased charge carrier density near the TPD/Alq(3) interface that results from enhanced electron tunneling, and removal of exciton-quenching gap states that are intrinsic to the Alq(3)/Al interface. (C) 1997 American Institute of Physics.