Axially Chiral TADF‐Active Enantiomers Designed for Efficient Blue Circularly Polarized Electroluminescence

Abstract The use of a chiral, emitting skeleton for axially chiral enantiomers showing activity in thermally activated delayed fluorescence (TADF) with circularly polarized electroluminescence (CPEL) is proposed. A pair of chiral stable enantiomers, (−)‐( S )‐Cz‐Ax‐CN and (+)‐( R )‐Cz‐Ax‐CN, was designed and synthesized. The enantiomers, both exhibiting intramolecular π‐conjugated charge transfer (CT) and spatial CT, show TADF activities with a small singlet–triplet energy difference (Δ E ST ) of 0.029 eV and mirror‐image circularly polarized luminescence (CPL) activities with large g lum values. Notably, CP‐OLEDs based on the enantiomers feature blue electroluminescence centered at 468 nm with external quantum efficiencies (EQEs) of 12.5 and 12.7 %, and also show intense CPEL with g EL values of −1.2×10 −2 and +1.4×10 −2 , respectively. These are the first CP‐OLEDs based on TADF‐active enantiomers with efficient blue CPEL.