One‐Step Intermolecular Oxidative Coupling and Cyclodehydration Strategy for Pure‐Green B,N,O‐Embedded Hetero[9]Helicene Emitter

ABSTRACT Helicenes are promising circularly polarized luminescence (CPL) candidates owing to their inherent chirality. In particular, B,N‐embedded heterohelicenes achieve superior exciton utilization via multiple‐resonance thermally activated delayed fluorescence, whereas their syntheses remain challenging. Herein, we present a facile strategy of one‐step intermolecular oxidative coupling and cyclodehydration to achieve the concise synthesis of a B,N,O‐embedded hetero[9]helicene ( BNFN ). BNFN exhibits narrowband green photoluminescence peaking at 516 nm with a rapid reverse intersystem crossing rate (3.76 × 10 5 s −1 ), and the enantiomers display intense CPL with dissymmetry factors ( g PL ) of +2.4/−2.6 × 10 −3 . Corresponding circularly polarized organic light‐emitting diodes (CP‐OLEDs) deliver CIE coordinates of (0.20, 0.72) and g EL of +3.4/−3.3 × 10 −3 . Notably, these devices demonstrate maximum external quantum efficiencies of 31.3%/30.2% and low efficiency roll‐off. This work paves the way toward the development of a novel B,N‐embedded heterohelicene for efficient CP‐OLEDs.