Propeller type dibenzofurocarbazole as a new rigid donor moiety for highly efficient and long living thermally activated delayed fluorescence emitters

A carbazole extended 15H-dibenzofuro[3,2-a:3′,2′-c]carbazole (dBFCz) was developed as a propeller type strong donor moiety of thermally activated delayed fluorescent (TADF) emitters. Two TADF emitters, 2-(15H-dibenzofuro[3,2-a:3′,2′-c]carbazol-15-yl)-5-(4,6-diphenyl-1,3,5-triazin-2-yl)benzonitrile (dBFCzCNTrz) and 15-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-15H-dibenzofuro[3,2-a:3′,2′-c]carbazole (dBFCzTrz), were synthesized using the dBFCz donor and diphenyltriazine acceptor. The dBFCzCNTrz and dBFCzTrz emitters showed high external quantum efficiency of 27.5% and 22.6% with short excited state lifetime, respectively. In particular, the dBFCz donor was much better than a common carbazole donor and benzofurocarbazole donor in enhancing the external quantum efficiency and device lifetime, which proposed that the dBFCz worked well as a donor moiety for TADF emitters.