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

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, (<italic>R/S</italic>)‐<bold>S‐AX‐BN</bold> and (<italic>R/S</italic>)‐<bold>SO2‐AX‐BN</bold>, 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. (<italic>R/S</italic>)‐<bold>S‐AX‐BN</bold> and (<italic>R/S</italic>)‐<bold>SO2‐AX‐BN</bold> 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 (|<italic>g</italic>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 (<italic>R/S</italic>)‐<bold>S‐AX‐BN</bold> and (<italic>R/S</italic>)‐<bold>SO2‐AX‐BN</bold> 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 |<italic>g</italic>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. [ABSTRACT FROM AUTHOR]