Progressive Enhancement of Circularly Polarized Luminescence in Chiral Hybrid Indium Halides via Incorporating NH ₄ ⁺ and Sb ³⁺ Ions for X‐ray Imaging

Abstract Chiral hybrid metal halides (CHMHs) have attracted extensive attention in the field of circularly polarized luminescence (CPL) due to their fascinating intrinsic chirality, simple synthetic method, and excellent photoelectric properties. However, it remains a huge challenge to simultaneously boost the CPL dissymmetry factor (g _lum ) and the photoluminescence quantum yield (PLQY). In this study, a pair of non‐emissive indium‐based CHMHs, namely (R/S‐C ₅ H ₁₃ NO) ₃ InCl ₆ , is first synthesized. Then, sequential incorporation of NH ₄ ⁺ and Sb ³⁺ ions progressively boosted self‐trapped exciton (STE) emission. The resultant (R/S‐C ₅ H ₁₃ NO) ₂ NH ₄ InCl ₆ :Sb (2‐R/SInSb) not only achieves near‐unity PLQYs but also exhibits remarkable g _lum of +9.4 × 10 ⁻³ /−9.1 × 10 ⁻³ . Experimental investigations reveal that the introduction of NH ₄ ⁺ increases the distortion of metal‐halogen octahedra, thus strengthening the STE emission. In addition, NH ₄ ⁺ can modulate the distribution of hydrogen bonds around inorganic octahedra and chiral cations, which is conducive to the transmission and amplification of chiral signals. Based on the efficient CPL characteristics, 2‐SInSb is further employed in a scintillation film, achieving a spatial resolution of 8.7 lp mm ⁻¹ and high‐quality X‐ray imaging. These findings highlight the potential of indium‐based CHMHs as high‐performance CPL emitters and underscore their promise for X‐ray imaging applications.