A Methodological Study on Tuning the Thermally Activated Delayed Fluorescent Performance by Molecular Constitution in Acridine-Benzophenone Derivatives.

Thermally activated delayed fluorescent (TADF) emitters are usually designed as donor-acceptor structures with large dihedral angles, which tend to incur low fluorescent efficiency, and therefore, through molecular design various strategies have been proposed to increase the efficiency of emitters; however, few studies have compared these strategies in one TADF system. In this study, a novel TADF molecule, [4-(9,9-diphenylacridin-10-yl)phenyl](phenyl)methanone (BP-DPAC), was designed as a prototype, and two derivatives, BP-Ph-DPAC and DPAC-BP-DPAC, were also prepared to represent two common approaches to enhance TADF performance. Compared with the maximum external quantum efficiency (EQE) of 6.82 % for BP-DPAC, organic light-emitting diodes (OLED) devices based on DPAC-BP-DPAC exhibited enhanced TADF properties with the highest maximum EQE of 18.67 %, owing to an additional diphenylacridine donor, whereas BP-Ph-DPAC showed non-TADF properties and exhibited the lowest EQE of 4.25 %, owing to the insertion of a phenyl ring between donor and acceptor.