A design strategy of bipolar host materials for more than 30 times extended lifetime in phosphorescent organic light-emitting diodes using benzocarbazole and quinazoline

Abstract

Stable host materials based on benzocarbazole and quinazoline were synthesized to establish a design strategy of bipolar hosts for elongated lifetime in orange phosphorescent organic light-emitting diodes (PHOLEDs). Three host materials with benzocarbazole and quinazoline connected directly or through a phenyl linker were compared in terms of the device lifetime of the orange PHOLEDs. The connection between benzocarbazole and quinazoline through a phenyl linker was an effective way of improving the lifetime of the red PHOLEDs by more than twice and the molecular orbital distribution of the hosts was well correlated with the lifetime of the PHOLEDs. In particular, the lifetime of the PHOLEDs was extended by more than 30 times compared to a conventional PHOLED with a common CBP host.