Effects of interlayers on phosphorescent blue organic light-emitting diodes

We demonstrate that the electroluminescence efficiencies of blue organic light-emitting diodes can be significantly enhanced by the incorporation of interlayers at the hole transporting layer (HTL)/emitting layer (EML) and/or EML/electron transporting layer (ETL) interfaces. Blue light-emitting iridium(III)bis(4,6-difluorophenyl)-pyridinato-$N,C2′$⁠) picolinate was doped in an $m$-bis-(triphenylsilyl)benzene (UGH3) host and hole transporting wide band gap materials were introduced between the HTL and the EML as interlayers in order to block triplet exciton quenching and reduce electron overflow. The effects of adding a second undoped UGH3 interlayer at the EML/ETL interface were also studied. When the appropriate interlayers were added, the device performances were found to be dramatically enhanced, with peak external quantum and power efficiencies of 20.1% and $29.2lm∕W$⁠.