0D Hybrid Cuprous Halide as an Efficient Light Emitter and X‐Ray Scintillator

Abstract Despite the extraordinary X‐ray scintillation performance of three‐dimensional (3D) lead perovskite nanocrystals (PNCs), the serious biotoxicity of Pb 2+ and luminescent instability in water remain insurmountable obstacles for their applications in medical imaging. To address these drawbacks, herein, the study demonstrates one new lead‐free zero‐dimensional (0D) hybrid cuprous halide of single‐crystalline [BzTPP] 2 Cu 2 I 4 (BzTPP = Benzyltriphenylphosphonium) as a satisfactory X‐ray scintillator. [BzTPP] 2 Cu 2 I 4 displays broadband yellowish‐green light emission with a high photoluminescent quantum yield (PLQY) of 44.2% and large Stokes shift of 167 nm upon UV light excitation. High PLQY and negligible self‐absorption enable [BzTPP] 2 Cu 2 I 4 to display impressive scintillation performance excited by X‐ray with a light yield of 27 706 photons MeV ‐1 and low detection limit of 0.352 µ Gy s −1 , surpassing typical 3D PNCs. More importantly, [BzTPP] 2 Cu 2 I 4 represents extraordinary structural and luminescent stability in water for at least one month. The excellent and stable radioluminescence performance as well as solution growth method ensure a [BzTPP] 2 Cu 2 I 4 ‐based screen for fine‐resolution X‐ray imaging with potential in radiography and inspection. This work highlights the multiple merits of low‐toxicity and cost, high light yield, and long‐term water‐stability of 0D hybrid cuprous halides as highly desirable X‐ray scintillators.