The effect of frontier orbital distribution of the core structure on the photophysics and device performances of thermally activated delayed fluorescence emitters

The effect of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) distribution of the core structure on the thermally activated delayed fluorescence (TADF) behavior of the TADF emitters was investigated. Dibenzofuran was used as the core structure of the TADF materials, and its 2 and 3 positions were substituted with a donor and an acceptor. Two TADF emitters with the donor and acceptor positions exchanged with each other were synthesized and suggested that the substitution of the donor at the LUMO dominant position and the acceptor at the HOMO dominant position is beneficial to improve the efficiency of the TADF OLEDs. It was described that the substitution positions of the donor and acceptor to the core structure should be managed to increase the quantum efficiency of the TADF devices by enlarged orbital overlap.