Multiple resonance thermally activated delayed fluorescence emitters containing novel S-based acceptor with narrowed FWHM and enhanced EQE

Multiple resonance thermally activated delayed fluorescence (MR-TADF) materials have extensive application in the field of optoelectronics because of their glamorous properties. Previously, MR-TADF molecular design strategies based on sulfur atom (S) have the deficiencies of broad full width at half maximum (FWHM) and low maximum external quantum efficiency (EQE max ). Thus, this work designed and synthesized a novel weak acceptor containing S atom N2SO and linked it with BCzBN to form a new MR-TADF material N2SOBN. N2SOBN exhibited emissions at 494 nm in toluene with photoluminescence quantum yields (PQLY) up to 98% in doped film. N2SOBN-based OLED both had the impressive merits of narrower FWHM (28 nm) and remarkable EQE max (28%), which had a cutting-edge position in the S-based MR-TADF materials. Surprisingly, N2SOBN enantiomers showcased circularly polarized photoluminescence (CPL) characteristics with dissymmetry factors (g PL ) up to 3.25 × 10 −4 /−2.91 × 10 −4 in toluene. This work provided a viable methodology for the research on S-based MR-TADF with narrower FWHM, enhanced EQE and chiroptical properties. • Design and synthesize a new MR-TADF emitter containing novel sulfur-based acceptor. • N2SOBN-based OLED demonstrates narrower FWHM (28 nm) and excellent EQE max (28.0%). • N2SOBN's CD and CPL spectra show excellent CPL traits with |g PL | up to 3.25 × 10 −4 . • N2SOBN's FWHM and EQE max have a leading position in the S-based MR-TADF materials.