Investigation of hole injection enhancement by MoO_3 buffer layer in organic light emitting diodes

摘要

An MoO_3 buffer layer prepared by thermal evaporation as hole injection layer was investigated in organic light emitting diodes. The MoO_3 film inserted between the anode and hole transport layer decreased the operating voltage and enhanced power efficiency. Introduction of 1 nm MoO_3 film, which was found to be the optimum layer thickness, resulted in 45% increase in efficiency compared with traditional ITO anode. Results from atomic force microscopy and photoemission spectroscopy showed that smooth surface morphology and suitable energy level alignment of ITO/MoO_3 interface facilitated hole injection and transport. The hole injection and transport mechanism at the ITO/MoO_3 interface in thin and thick buffer layers were analyzed.