Axially Chiral Multiple Resonance Thermally Activated Delayed Fluorescence Enantiomers for Efficient Circularly Polarized Electroluminescence

Abstract

The chiral materials and circularly polarized organic light‐emitting diodes (CP‐OLEDs) have potential applications in 3D display due to the generation of circularly polarized luminescence (CPL). However, achieving a combination of chirality, high efficiency, and narrowband emission for thermally activated delayed fluorescence (TADF) materials has proven to be a challenging endeavor, often involving complicated synthesis and chiral separation processes. In this study, a simple design approach is introduced by direct connection of the multiple resonance (MR) skeleton and chiral (R/S)‐1,1′‐binaphthyl units, obtaining two pairs of chiral MR‐TADF enantiomers (R/S)‐DtCzB‐OBN and (R/S)‐DtCzB‐BN without chiral resolution. These enantiomers exhibit blue‐green emissions with photoluminescence quantum efficiencies of up to 98% in doped films and full‐width at half‐maximum of 22 nm both in toluene and in the device. Furthermore, (R/S)‐DtCzB‐OBN and (R/S)‐DtCzB‐BN display symmetric CPL spectra with dissymmetry factors (gPL) of + 3.86( ± 0.317) × 10−4/‐3.37( ± 0.317) × 10−4 and + 7.09( ± 0.233) × 10−4/‐7.74(± 0.233) × 10−4, respectively. The CP‐OLEDs based on (R/S)‐DtCzB‐OBN and (R/S)‐DtCzB‐BN exhibit impressive maximum external quantum efficiencies of 30.0% and 33.9%, as well as gEL factors of +3.40( ± 0.362) × 10−4/‐3.11( ± 0.362) × 10−4 and + 7.99( ± 0.391) × 10−4/‐8.19( ± 0.391) × 10−4, respectively. This research proposes a strategy for directly constructing chiral MR‐TADF materials for high‐performance CP‐OLEDs, avoiding complicated chiral separation.