Triplet bipolar host materials for solution processed organic light-emitting devices

Two solution-processible new triplet bipolar host molecules, 4,4′-bis[N-(1-naphthyl)-N(3-pyridinylamino]biphenyl (NPyB) and 4,4′-bis [N-(3-quinolinyl)-N-phenylamino]biphenyl (QuPB) were synthesized and characterized for phosphorescent organic light-emitting diodes (PHOLEDs). They exhibit good triplet energies as 2.3–2.4 eV for red PHOLEDs and show good amorphous film characteristics with high solubility, allowing a solution processing. The NPyB and QuPB hosts were evaluated for soluble red PHOLEDs with ITO/PEDOT:PSS/Ir complex:host/TPBI/LiF/Al structure. A maximum light output of 14,440 cd/m2, driving voltage of 5.9 V, external quantum efficiency of 14.2%, and maximum current/power efficiencies of 21.0 cd/A and 11.3 lm/W have been achieved by NPyB host and bis(2-phenylquinoline(acetylacetonate)iridium (Ir(phq)2acac) red dopant.