| 초록 |
We report efficient green phosphorescent organic light-emitting diodes using exciton blocking layer(EBL) between hole transport layer and emitting layer. Carbazole based(4,4’-N,N’-dicarbazole)biphenyl(CBP) and spirobifluorene based PH1 were used as host materials and CBP and 4,4’,4’-tris(N-carbazolyl)triphenylamine(TCTA) were introduced between hole transport layer(HTL) and emitting layer(EML) to block triplet exciton quenching and electron overflow to HTL. The efficiency of both CBP and PH1 host with TCTA EBL in the devices increased compared to the standard devices, while only PH1 host with CBP EBL structure showed improved efficiency. PH1 with CBP EBL device showed best quantum efficiency value of 18% and PH1 with TCTA EBL also exhibited high efficiency of 16% compared with 3.1% of PH1 standard devices at 1000 cd/m2. |
