Efficient non-doped blue light emitting diodes based on novel carbazole-substituted anthracene derivatives

In this study, we synthesized three anthracene derivatives featuring carbazole moieties as side groups -2-tert-butyl-9,10-bis[4-(9-carbazolyl)phenyl]anthracene (Cz(9)PhAnt), 2-tert-butyl-9,10-bis{4-[3,6-di-tert-butyl-(9-carbazolyl)]phenyl}anthracene (tCz(9)PhAnt), and 2-tert-butyl-9,10-bis{4'-[3,6-di-tert-butyl-(9-carbazolyl)]biphenyl-4-yl}anthracene (tCz(9)Ph(2) Ant) - for use in blue organic light emitting devices (OLEDs). The anthracene derivatives presenting rigid and bulky tert-butyl-substituted carbazole units possessed high glass-transition temperatures (220 degrees C). Moreover, the three anthracene derivatives exhibited strong blue emissions in solution, with high quantum efficiencies (91%). We studied the electroluminescence (EL) properties of non-doped OLEDs incorporating these anthracene derivatives, with and without a hole-transporting layer (HTL). OLEDs incorporating an HTL provided superior EL performance than did those lacking the HTL. The highest brightness (6821 cd/m(2)) was that for the tCz(9)PhAnt-based device; the greatest current efficiency (2.1 cd/A) was that for the tCz(9)Ph(2)Ant-based device. The devices based on these carbazole-substituted anthracene derivatives also exhibited high color purity. (C) 2011 Elsevier B. V. All rights reserved.