Axial Chiral Biphenyl MR‐TADF Enantiomers for Efficient Narrowband Circularly Polarized Electroluminescence

Abstract Circularly polarized multi‐resonance thermally activated delayed fluorescence (CP‐MR‐TADF) materials, capable of achieving circularly polarized luminescence (CPL), play a crucial role in the field of 3D display. In this study, two pairs of axial chiral MR‐TADF enantiomers, ( R/S )‐ S‐AX‐BN and ( R/S )‐ SO 2 ‐AX‐BN , are synthesized by fusing biphenyl skeletons containing sulfur/sulfone with classic B/N‐embedded polycyclic aromatic hydrocarbons. These compounds exhibit good photophysical properties with intense CPL. ( R/S )‐ S‐AX‐BN and ( R/S )‐ SO 2 ‐AX‐BN display green photoluminescence, with peaks at 489 and 495 nm, full‐width at half‐maximum (FWHM) values of 21 and 20 nm in toluene, and dissymmetry factors (| g PL |) of 3.5 × 10 −3 and 2.3 × 10 −3 in doped films, respectively. Additionally, circularly polarized organic light‐emitting diodes (CP‐OLEDs) fabricated from ( R/S )‐ S‐AX‐BN and ( R/S )‐ SO 2 ‐AX‐BN exhibit narrow electroluminescence (EL) spectra with FWHMs of 22 and 21 nm. These CP‐OLEDs achieve high maximum external quantum efficiencies of 33.5% and 31.5%, with relatively low efficiency roll‐offs. Furthermore, they exhibit high | g EL | factors of 3.3 × 10 −3 and 2.2 × 10 −3 , respectively, representing the highest values among axial chiral analogs. This work introduces a novel approach for designing axial chiral CP‐MR‐TADF molecules and provides a reference for fabricating narrowband CP‐OLEDs with high efficiency and intense CPL.