Synthesis of host materials for blue phosphorescent organic light emitting diodes (OLEDs) with high efficiency and low driving voltage

Blue host materials for phosphorescent organic light-emitting diodes (PHOLEDs) were synthesized with carbazole as a donor moiety and a-carboline as an accepter moiety to assign bipolar property. Synthesized carbazole-carboline core was modified with benzonitrile, phenyl and carbazole to control charge transport property. The host materials showed high triplet energy above 2.85 eV, and their highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital energy levels (LUMO) were -5.90/-2.79, -5.90/-2.72 and -5.89/-2.67 eV, respectively, depending on the substituent of the core structure. Maximum quantum efficiencies of 23.4%, 19.6% and 17.4% were obtained with low driving voltage in blue PHOLEDs using the new host materials.