High hole mobility hole transport material for organic light-emitting devices

A new hole-transporting material, 5,10,15-triphenyl-5H-diindolo[3,2-a:3′,2′-c]carbazole (TPDI) is reported for organic light-emitting device (OLED) applications. It shows excellent hole mobility (6.14 × 10−3 cm2/V s), one order higher than that of NPB (4,4′-bis(N-phenyl-1-naphthylamino)biphenyl), and a good HOMO level of 5.3 eV. Fabricated fluorescent blue OLEDs exhibit about 1.0 V voltage reduction and 18% external quantum efficiency (EQE) improvement by replacing TPDI instead of NPB as a hole transport layer. In the green phosphorescent OLEDs, the driving voltage improves about 1.8 V and EQE increases about 65%. This TPDI will be applicable to not only in fluorescent OLEDs but also in phosphorescent OLEDs.