Efficient Circularly Polarized Electroluminescence Based on Chiral MR‐TADF Materials with Innovative Planar Structure Design Strategy

Abstract Chiral multiple resonance thermally activated delayed fluorescence (CP‐MR‐TADF) emitters have obtained attention due to their potential in organic light‐emitting diodes (CP‐OLEDs) with circularly polarized luminescence (CPL). Moreover, the devices always rely on the doping concentration due to the concentration aggregation‐caused quenching of CP‐MR‐TADF emitters. Herein, three MR‐TADF materials (p‐ICz‐N‐BN, m‐ICz‐N‐BN and m‐prCz‐N‐BN) are presented by face‐to‐face arrangement of indolo[3,2,1‐jk]carbazole and MR‐TADF fluorophore sterically on naphthalene bridge, showing emissions peaking at 496–499 nm with full‐width at half‐maximum values of 23–26 nm and photoluminescence quantum yields of 91%–98%, respectively. Because of the asymmetric and steric hindrance structures, both m‐ICz‐N‐BN and m‐prCz‐N‐BN are separated into innovative planar enantiomers, exhibiting symmetric CPL spectra with dissymmetry factors (|g_PL|) of up to 1.1 × 10⁻³ and 2.3 × 10⁻³ in toluene and films, respectively. Furthermore, the OLEDs with p‐ICz‐N‐BN, m‐ICz‐N‐BN, and m‐prCz‐N‐BN illustrate maximum external quantum efficiencies of 31.5%, 33.7%, and 32.4%, respectively, and still remain at high levels even at the 20 wt.% doping concentration with almost unchanged emission spectra. Additionally, the CP‐OLEDs with R/S‐m‐ICz‐N‐BN and R/S‐m‐prCz‐N‐BN display |g_EL| factors of 1.88 × 10⁻³ and 1.89 × 10⁻³, respectively.