Coupling Axial Chirality with Through‐Space Charge‐Transfer‐Involved Excited‐State Regulation in Bicarbazole‐Based Blue CP‐OLED Emitters

Blue circularly polarized organic light‐emitting diodes (CP‐OLEDs) remain challenging because efficient triplet harvesting and strong electroluminescence dissymmetry must be achieved within a single chiral emitter. Herein, an axial‐chirality‐assisted thermally activated delayed fluorescence emitter, Zooey‐TRZ, is developed by incorporating a sterically constrained bicarbazole‐based chiral axis with the triazine acceptor. The axially locked bicarbazole scaffold participates directly in the electronic structure, giving rise to through‐space charge‐transfer‐involved excited states, a reduced singlet‐triplet energy gap, and spin‐orbit coupling‐active triplet‐to‐singlet conversion pathways. In doped films, concentration‐ and host‐polarity‐dependent interactions regulate excited‐state energetics and reverse intersystem crossing, while stronger environmental polarity weakens circularly polarized luminescence, revealing a balance between triplet harvesting and chiroptical response. Single‐crystal analysis suggests slipped donor‐acceptor packing consistent with J‐aggregation‐like interactions. Enantiopure CP‐OLEDs exhibit blue electroluminescence at 455 nm, maximum external quantum efficiencies of 21.14% and 20.42%, and opposite electroluminescence dissymmetry factors of +7.03 × 10 −3 and −7.05 × 10 −3 . These results establish axially locked bicarbazole as an effective platform for excited‐state engineering in efficient blue circularly polarized emitters.