Designing Versatile Sulfoximine as Accepting Unit to Regulate the Photophysical Properties of TADF Emitters towards High-performance OLEDs

Abstract This contribution describes sulfoximine (SFI) derivatives as a novel type of acceptor for efficient thermally activated delayed fluorescence (TADF) emitters. SFI presents a unique advantage by facile introduction of versatile functionalities on its secondary amine, which allows delicate manipulation of TADF properties. In a proof of principle study, three green/yellowish green TADF emitters, namely DMAC-SFIP, DMAC-SFIC and DMAC-SFIS were developed with different electron-withdrawing N-substituents based on simple donor-acceptor (D-A) typed structure. A look into the molecular conformations indicates the existence of different types of weak intramolecular interactions to suppress nonradiative decay. More importantly, effective mixing between charge transfer (CT) and locally excited (LE) triplet states is observed for DMAC-SFIP, DMAC-SFIC due to suitable electron-deficiency in the SFI segment, resulting in acceleration of the reverse intersystem crossing (RISC) rate. Consequently, these new TADF emitters render excellent organic light-emitting diode (OLED) performances with external quantum efficiencies (EQEs) up to 20.4% and small efficiency roll-off.