LAUSR

Helicene‐based circularly polarized luminescence (CPL) materials suffer from severely low color purity in circularly polarized organic light‐emitting diodes (CP‐OLEDs). Here, a novel molecular engineering strategy is introduced by replacing helicene containing continuous fused benzene rings with a multiple resonance (MR) framework comprising discontinuous fused benzene rings. This approach effectively suppresses high‐frequency C─C bond stretching vibrations and enhances short‐range charge transfer, enabling high color purity, CPL activity, and efficient thermally activated delayed fluorescence (TADF). The proof‐of‐concept green BN[7]helicene‐based emitters (P/M)‐DBN‐mICz display bright and narrowband green emission peaking at 512 nm with a full‐width at half‐maximum (FWHM) of 25 nm. Notably, the enantiomers (P)‐ and (M)‐DBN‐mICz exhibit narrowband CPL spectra with FWHMs of 26 and 25 nm, the Commission Internationale de l'Éclairage (CIE) coordinates of (0.14, 0.72) and (0.15, 0.72), and photoluminescence dissymmetry factors of +2.3 × 10−3 and −2.6 × 10−3. (P)‐ and (M)‐DBN‐mICz‐based CP‐OLEDs deliver pure‐green emission, characterized by a peak wavelength of 516 nm, a narrow FWHM of 27 nm, and CIE coordinates of (0.17, 0.72), representing the purest green CP‐OLEDs reported to date. Furthermore, these devices exhibit high electroluminescence dissymmetry factors of +5.3 × 10−3/−8.5 × 10−3, and maximum external quantum efficiencies of 37.3% and 36.6%, respectively.