Highly Efficient Phosphorescent Organic Light-Emitting Diodes Using Alkyl-Substituted Iridium Complexes as a Solution-Processible Host Material

We fabricated highly efficient organic light-emitting diodes (OLEDs) using the solution processible iridium complexes which have long alkyl or cycloalkyl substituents in an ancillary ligand as a host material and a red phosphorescent iridium complex as an emitting guest by spin coating method. The OLEDs emitted red phosphorescence from the guest and the luminance reached around 10,000 cd/m2. The efficiency of the OLED improved after we added an electron transport material (ETM) to the emitting layer. The OLED using a mixture of the alkyl substituted iridium complex and ETM as the host showed an external quantum efficiency of 10%.