High‐Quality, Large‐Size Cs ₂ ZnCl ₄ Halide Perovskite Scintillation Single‐Crystal Crystallized from Water

ABSTRACT Halide perovskite single crystals are emerging as great candidates for scintillation detection due to their remarkable luminescent properties. However, most halide single‐crystals reported to date have been grown using the Bridgman method, and their crystal quality and properties are significantly affected by impurities, depending heavily on costly ultra‐pure raw materials. Herein, we have developed an innovative water solution method enabling the growth of oversized (∼30 × 30 × 30 mm ³ ) Cs ₂ ZnCl ₄ single‐crystal with natural crystal faces in water, achieving exceptional crystal quality (FWHM = 50.4'') without requiring ultra‐pure raw materials, thereby effectively resolving the challenge of high‐quality crystal growth for this single‐crystal. In marked contrast to previously reported results, the Cs ₂ ZnCl ₄ single‐crystal grown exhibits a larger bandgap value (5.0 eV), distinctly different single‐peak emission, higher light yield, and a fully ultrafast scintillation decay (1.8 ns). Additionally, we unexpectedly discovered that the grown Cs ₂ ZnCl ₄ single‐crystal exhibits high transmittance (∼90%) over an ultra‐wide wavelength range of 260 nm to 15 µm, highlighting its immense potential as a high‐performance optical window material. This research highlights the successful growth of the first halide perovskite scintillation single‐crystal (Cs ₂ ZnCl ₄ ) in water, which will inform the future development of other high‐performance scintillation crystals in aqueous environments.