Effect of nitrogen position of carboline on the device performances of blue phosphorescent organic light-emitting diodes

A delta-carboline derived compound, 5-(3'-(9-carbazolyl)-[1,1'-biphenyl]-3-yl)pyrido[3,2-b]indole, was synthesized as a high triplet energy bipolar host material for blue phosphorescent organic light-emitting didoes and it was compared with alpha-carboline derived host material with the same backbone structure. The delta-carboline derived host material showed better electron transport properties than the host with alpha-carboline due to better electron accepting properties. Therefore, the new host material reduced driving voltage and increased the power efficiency of blue phosphorescent organic light-emitting diodes compared to a standard host with alpha-carboline moiety. A high external quantum efficiency of 25.3% and a high power efficiency of 36.4lm/W were achieved in the blue phosphorescent organic light-emitting diodes. (c) 2015 Elsevier B.V. All rights reserved.