High efficiency blue phosphorescent organic light emitting diodes using a simple device structure

High efficiency blue phosphorescent organic light emitting diodes have been developed by using a simple device structure. A derivative of spirobifluorene based phosphine oxide was used both as a host and an electron transport layer with an exciton blocking function. A maximum quantum efficiency of 19.2% and a current efficiency of 37.2 cd/A were obtained by using a simple device structure without a hole blocking layer.