Molecular design of large-bandgap host materials and their application to blue phosphorescent organic light-emitting diodes

New large-bandgap host materials with carbazole and carboline moieties were designed and synthesized for high-performance blue phosphorescent organic light-emitting diodes (PhOLEDs). The two kinds of host materials, 9-(4-(9H-carbazol-9-yl) phenyl)-6-(9H-carbazol-9-yl)-9H-pyrido[2,3-b] indole (pP2CZCB) and 9-(3-(9H-carbazol-9-yl) phenyl)-6-(9H-carbazol-9-yl)-9H-pyrido[2,3-b] indole (mP2CZCB), displayed promisingly high triplet energies of similar to 2.92-2.93 eV for enhancing the exothermic energy transfer to bi s[2-(4,6-difluorophenyl) pyridinato-C-2, N](picolinato) iridium(III) (FIrpic) in PhOLED devices. It was found that the blue PhOLEDs bearing the new host materials and the FIrpic dopant exhibited markedly higher external quantum efficiencies (EQEs) than a device made with 1,3-bis(N-carbazolyl) benzene (mCP) as the host. In particular, the PhOLED device made with 3 wt% FIrpic as the dopant and mP2CZCB as the host material displayed a low driving voltage of 4.13 V and the high EQE of 25.3% at 1000 cd m (2). (C) 2015 Elsevier B.V. All rights reserved.