Boosting Photovoltaic Respond Through Molecular Engineering in Organic Manganese (II) Bromide for High‐Sensitivity X‑Ray Detection

Abstract Zero‐dimensinoal (0D) manganese‐based metal halides (MHs) demonstrate excellent structural tunable through organic cation design, enabling precise control of Mn─Mn distances to modulate critical photoelectric physical properties. Here, two novel 0D PTA ₂ MnBr ₄ (PTA = phenyltrimethylammonium) are synthesized and DMA ₂ MnBr ₄ (DMA = dimethylammonium) wafer with a manipulation of octahedra are synthesized by a precise molecular design. Structural analysis reveals that the PTA‐functional group with extended π ‐conjugation lengths increases the Mn─Mn distance, results in a lower energy transfer and reduced exciton binding energy compared to DMA⁺ (linear carbon chain). Consequently, PTA ₂ MnBr ₄ demonstrates an enhanced photoluminescence quantum yield and prolonged exciton lifetime. The engineered X‐ray detector based on PTA ₂ MnBr ₄ wafer exhibits a higher sensitivity of 1122 µC Gy _air ⁻¹ cm ⁻² and a lower detection limit of 95 nGy _air s ⁻¹ , while DMA ₂ MnBr ₄ device are 708.2 µC Gy _air ⁻¹ cm ⁻² and 180 nGy _air s ⁻¹ , respectively, which paves the way for high‐efficiency photoelectronic applications. This suggests that molecular engineering is a robust approach for designing high‐performance 0D manganese halides for radiation detection.