Bipolar host materials with carbazole and dipyridylamine groups showing high triplet energy for blue phosphorescent organic light emitting diodes

A series of new bipolar host materials with carbazole and different number of dipyridyl amine groups were synthesized for blue phosphorescent organic light-emitting diodes (PHOLEDs). Especially, we applied dipyridyl amine to control the polarity as well as electron transporting property of the carbazole based host materials for comparison with the properties of 1,3-di(9H-carbazol-9-yl)benzene (mCP). As a result, all the carbazole based host materials with dipyridyl amine moieties showed very high triplet energies (>2.9 eV) as well as wide band gap (>3.5 eV). Thus, the blue phosphorescent devices employing those materials with bis(4,6-difluorophenyl pyridinato-N,C2)picolinato-iridium (III) (Flrpic) as a dopant and we obtained moderately high external quantum efficiency (EQE) up to 21.6% with N-(3,5-di(9H-carbazol-9-yl)phenyl)-N-(pyridin-2-yl)pyridin-2-amine (DCPPy). (C) 2017 Elsevier Ltd. All rights reserved.