Novel aromatic extended carbazoles as a chemical platform of bipolar hosts for improved lifetime in phosphorescent organic light-emitting diodes

Novel aromatic extended carbazoles, 9H-fluoreno[9,1-bc]carbazole, 9H-dibenzo[a,c]carbazole, and 15H-phenanthro[9,10-a]carbazole, were developed as donor moieties constructing bipolar host materials for phosphorescent organic light-emitting diodes. The 9H-fluoreno[9,1-bc]carbazole, 9H-dibenzo[a,c]carbazole, and 15H-phenanthro[9,10-a]carbazole implemented hosts showed high glass transition temperature, bipolar charge transport character, and triplet energy for energy transfer to red phosphorescent emitters. The hosts built on the aromatic extended carbazoles and quinazoline greatly improved the lifetime of red phosphorescent organic light-emitting diodes while enhancing the quantum efficiency. The material characterization data and device analysis results confirmed that the aromatic extended carbazole based host materials are effective to extend the lifetime of the red phosphorescent devices by thermal stability and polaron stability.