Structural Design and Performance Prediction of Zero‐Dimensional Manganese (II) Halide Scintillators for X‐Ray Imaging: A Case Study of (C ₃₃ H ₂₉ NP) ₂ MnBr ₄ ·EtOH

Abstract The discovery and rational design of high‐performance scintillator materials are crucial for advancing X‐ray imaging and detection technologies, and yet remain a significant challenge. Herein, a highly efficient 0D hybrid Mn ²⁺ ‐based scintillator (C ₃₃ H ₂₉ NP) ₂ MnBr ₄ ·EtOH (CZTPPM) is presented by introducing a rigid and bulky organic salt (3‐(carbazol‐9‐yl)propyl) triphenylphosphonium C ₃₃ H ₂₉ NP ⁺ Br ⁻ (CZTPPBr). X‐ray single‐crystal structural analysis shows a minimal Mn–Mn distance of exceeding 11 Å, among segregated MnBr ₄ ²⁻ luminescent centers. Consequently, under UV excitation, CZTPPM exhibits an intense green emission with a near‐unity photoluminescence quantum yield of 99.2% and reduced thermal quenching characteristic (I _{320 K} = 86.9% I _{80 K} ). Moreover, the CZTPPM crystals demonstrate outstanding X‐ray scintillation properties, producing a high light yield of 56 363 photons MeV ⁻¹ , a low detection limit of 55.73 nGy _air s ⁻¹ , and a narrow spatial resolution of 15.5 lp mm ⁻¹ with a great potential for high‐quality X‐ray imaging. Taking into consideration PLQY and X‐ray absorption coefficients simultaneously, the concept of areal density (σ) is further introduced to evaluate the scintillation efficiencies in 0D hybrid manganese bromides, which may be useful as an intuitive structural criterion for prediction.