Structural Modulation Reduces Carrier Localization and Enhances Organic‐Inorganic Coupling to Improve Charge Transport in Hybrid Manganese Halide X‐Ray Detectors

ABSTRACT Zero‐dimensional (0D) organic‐inorganic hybrid manganese halides (OIHMnHs) have garnered significant interest for direct X‐ray detection due to their low ion mobility, excellent optoelectronic properties, and environmental friendliness. However, the isolated nature of their inorganic polyhedra inherently limits carrier transport capacity. Therefore, enhancing the coupling between organic cations and inorganic polyhedra to improve carrier transport is crucial, yet technically challenging, for advancing high‐performance X‐ray detectors. Here, the 0D TMPA ₂ MnBr/Cl ₄ (TMPA, trimethylphenylammonium) single crystals (SCs) are reported, in which theoretical calculations reveal that the A‐site cation in TMPA ₂ MnBr ₄ primarily contributes to the conduction band minimum (CBM), which facilitates the establishment of a multidimensional carrier transport channel between [MnBr ₄ ] ²⁻ and [TMPA] ⁺ . Meanwhile, the optimized TMPA ₂ MnBr ₄ reduces carrier localization within the inorganic polyhedron through structural modulation, enhancing organic‐inorganic coupling and thereby improving carrier transport capacity and X‐ray detector performance. Consequently, the resulting TMPA ₂ MnBr ₄ SC detector demonstrates remarkable performance with high sensitivity (1.04 × 10 ⁵ µC Gy _air ⁻¹ cm ⁻² ) and a low detection limit of 72.6 nGy _air s ⁻¹ . Notably, the device exhibits superior operational stability (8060 µC Gy _air ⁻¹ cm ⁻² , 373 K). This work lays the foundation for advancing environmentally friendly X‐ray detectors with high sensitivity, excellent thermal stability, and enhanced commercial viability for medical imaging applications.