Controlling of Circularly Polarized Luminescence via Modulating the Angle Between Transition Electric and Magnetic Dipole Moments

Abstract The most challenging task in the development of chiral luminescent materials is currently increasing the dissymmetry factors (g_PL, g_EL) of circularly polarized luminescence (CPL). Current research primarily focuses on enhancing the molecular transition magnetic dipole moment, while the angle between the transition electric and magnetic dipole moment (θ_e,m) has received comparatively limited attention. In this study, two pairs of intrinsically axial chiral fluorescence (CP‐MR‐F) and thermally activated delayed fluorescence (CP‐MR‐TADF) enantiomers (R/S‐BBCz‐BN and R/S‐OBBCz‐BN) with increased g factors by modulating θ_e,m are reported. Based on R/S‐5H,5′H ‐6,6′‐bibenzo[b]carbazole units, the theoretically calculated θ_e,m and g_cal for S‐BBCz‐BN are 17.7° and 1.1 × 10⁻², respectively, enabling excellent CPL properties with |g_PL| of 5.8 × 10⁻³ in toluene, representing one of the highest g values among MR materials. By employing the less conjugated R/S‐7,7′,8,8′,9,9′,10,10′‐octahydro‐5H,5′H‐6,6′‐bibenzo[b]carbazole groups with better electron donating ability, R/S‐OBBCz‐BN demonstrate good MR‐TADF and CPL properties with a peak at 467 nm, a full width at half‐maximum of 27 nm, and |g_PL| of 2.5 × 10⁻³. Furthermore, the optimized circularly polarized organic light‐emitting diodes based on these two pairs of enantiomers showcase high maximum external quantum efficiencies of 24.7%/33.3% and mirror symmetrical circularly polarized electroluminescence with |g_EL| factors of 3.4/1.2 × 10⁻³, respectively.