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.