Chiral sulfoximine-based TADF emitter for circularly polarized luminescence and highly efficient OLEDs

This work describes the first example of circularly polarized thermally activated delayed fluorescent (CP-TADF) materials containing heteroatomic stereocenter. A pair of central chiral enantiomers, namely (R)-FAC-SIC and (S)-FAC-SIC, were assembled by sulfoximine-based acceptor and acridan-based donor in a highly twisted manner. The assymetric sulfur atom served as a chiral source, enabling the emitters with distinct circular dichroism (CD) and circularly polarized luminescence (CPL) signals. Benefited from the close-lying excited-state energy levels and multiple intra-/intermolecular interactions in film state, the enantiomers possessed highly efficient TADF emission with almost unit quantum yield (ФPL). Consequently, the corresponding device showed excellent maximum external quantum efficiency (EQEmax) of 28.5 %, current efficiency (CEmax) of 85.6 cd/A, and power efficiency (PEmax) of 84.0 lm W−1. We believe the introduction of heteroatom-based central chirality would significantly broaden the design scope of high-performance CP-TADF emitters.