Applications of metal oxides in the contact systems of organic electronic devices

Abstract

Metal oxides are a group of materials that have shown great promise in improving the efficiency of devices based on organic materials through inclusion in the contact structures of such devices. In this work, the deposition technique of spray pyrolysis is developed for use for the deposition of doped zinc oxide films and molybdenum oxide films. Spray pyrolysis is of great interest as a technique for use in the organic electronics field due to its cost, scalability and compatibility with other solution processing techniques. This makes the technique particularly interesting for use in devices intended for large scale applications such as lighting The study of doped zinc oxide focuses on its application as an alternative transparent conducting layer to the standard indium tin oxide layer. The zinc oxide layer was doped with aluminium to increase its conductivity, and the effect of lithium doping was investigated with the intent of improving the conductivity of the layers further. Annealing of the layers in a nitrogen environment was found to produce layers of a similar conductivity to that of indium tin oxide and the lithium doping was found to result in higher conductivities in annealed layers. The study of molybdenum oxide focuses on its application as a hole injection layer included in the anode contact of organic light emitting diodes. The deposition temperature was found to have a large effect on the resulting device efficiencies. This effect was determined to be due to variation of the work function and ion ratios present in the molybdenum oxide layer with deposition temperature. This work resulted in the fabrication of devices with efficiencies double that of the standard solution processed hole injection layer.