Highly efficient triazine/carbazole-based host material for green phosphorescent organic light-emitting diodes with low efficiency roll-off

Two novel host materials, 3-(dibenzo[b,d]furan-4-yl)-9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9H-carbazole (BFTC) and 3-(dibenzo[b,d]thiophen-4-yl)-9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9H-carbazole (BTTC) were designed and synthesized. These two compounds exhibited excellent physical properties with high thermal stabilities and reasonable HOMO-LUMO energy levels. Both of them were applied to fabricate green phosphorescent organic light emitting devices (PhOLEDs) as host materials, and the BTTC based device demonstrated outstanding electroluminescence performance with a maximum current efficiency, maximum power efficiency and external quantum efficiency of 69.3 cd A^-1, 54.2 lm W^-1 and 21.9%, respectively, suggesting that BTTC is a promising host for green PhOLEDs.