Electronic and chemical properties of molybdenum oxide doped hole injection layers in organic light emitting diodes

The origins of barrier lowering leading to high efficient organic light emitting devices with incorporation of molybdenum oxide (MoOx) in anode structures are investigated. Ultraviolet and x-ray photoemission spectra reveal that p-type doping effects in the organic films and carrier concentration increase at the anode interfaces cause the hole injection barrier lowering. The gap states, which help carrier injection from the anodes, resulted from the oxygen deficiency in MoOx due to the interaction of organic materials and MoOx.