Benzocarbazole and diphenyltriazine derived hosts for red phosphorescent organic light-emitting diodes

A bipolar host design for red phosphorescent organic light-emitting diodes (PhOLEDs) was explored as an objective to improve the external quantum efficiency and device lifetime. Main direction of the host design was to secttre low triplet energy, bipolar charge transport properties, and stability under positive and negative polarons. The objective of the host development was attained by a host design featured by low triplet energy benzocarbazole hole transport unit and diphenyltriazine electron transport unit. Two hosts with the benzocarbazole and diphenyltriazine linked through para or meta positions of the phenyl unit demonstrated a triplet energy of 2.52 eV and bipolar carrier transport properties. Based on the benzocarbazole and diphenyltriazine derived hosts, high external quantum efficiency over 23% and more than 30 times extension of the device lifetime were achieved in the red PhOLEDs.