Molecular engineering of blue diphenylsulfone-based emitter with aggregation-enhanced emission and thermally activated delayed fluorescence characteristics: impairing intermolecular electron-exchange interactions using steric hindrance

• A high-efficiency asymmetrical blue emitter with TADF, AEE and weak intermolecular electron-exchange interactions behaviors is demonstrated. • The relationship between structure and photo-induced and electro-induced behaviors was studied at the molecular perspective. • The efficiencies of blue non-doped OLED were 20.3% and 47.4 cd A -1 . Thermally activated delayed fluorescence (TADF) emitters with aggregation-enhanced emission (AEE) characteristics are in high demand in organic light-emitting diodes (OLEDs) because of their strong fluorescence and high exciton utilization under electrical excitation. In this work, an AEE-active TADF emitter, 10,10'-(5-((9-phenyl-9 H -carbazol-3-yl)sulfonyl)-1,3-phenylene)bis(9,9-dimethyl-9,10-dihydroacridine) ( CZ-DPS-BAD ), adopting diphenylsulfone skeleton as electron-accepting segment and 9-phenylcarbazole and 9,9-dimethyl-9,10-dihydroacridine as electron donors is developed. The small singlet-triplet splitting (0.13 eV) and high photoluminescence quantum yield (82%) of CZ-DPS-BAD can attribute to the formation of large dihedral angles between electron donor-acceptors and weak electron-exchange interaction that suppress concentration quenching and exciton annihilation. The assigned characteristics result in reverse intersystem crossing rate of up to 5.0 × 10 5 s -1 and a delayed fluorescence lifetime of 5.3 μs. Notably, CZ-DPS-BAD behaves excellent non-doped OLED performance with the emission peak of 486 nm, the maximum current efficiency of 47.4 cd A -1 , the maximum power efficiency of 46.1 lm W -1 , the maximum external quantum efficiency of 20.3%, and the exciton utilizin efficiency of 83%. It was also found that the short delayed fluorescence lifetime impair the triplet exciton annihilation resulting small efficiency roll-off in OLED. This work provides a general approach to explore new efficient and stable emitters by rationally regulating intermolecular interactions and integrating AEE and TADF, which facilitates their applications in optoelectronics.