High efficiency phosphorescent organic light-emitting diodes using carbazole-type triplet exciton blocking layer

Device performances of green phosphorescent organic light-emitting diodes using ($4,4^{\prime }\text{-}N,N^{\prime }$ -dicarbazole)biphenyl (CBP) and $N,N^{\prime }$ -dicarbazolyl-3,5-benzene (mCP) as an exciton blocking layer were investigated. CBP and mCP were introduced between hole transport layer and emitting layer to block triplet exciton quenching and efficient hole transport to emitting layer. The efficiency of green devices could be improved by more than three times by using mCP exciton blocking layer.