Low-cost aqueous-solution growth of high-performance Cs3Cu2I5:Mn single-crystal scintillators

The fabrication method defines the performance ceiling of scintillator materials. A breakthrough in low-cost aqueous-solution growth has recently enabled the production of Mn2+ doped Cs3Cu2I5 single-crystal scintillators with record-breaking performance. As reported in Advanced Materials (2023), a carefully controlled aqueous-solution method yields crystals with a high light yield of 95,772 photons/MeV under 137Cs γ-ray excitation and an excellent energy resolution of 3.79% at 662 keV.1 These performances, achieved without high-temperature furnaces or ultrahigh-purity raw materials, establish aqueous-solution growth as a transformative approach for producing next-generation radiation detectors.

Scintillators that convert high-energy photons or particles into visible light are indispensable in medical imaging, nuclear safety, high-energy physics, and space exploration. For decades, the search for an “ideal” scintillator—one that combines high light yield, fast scintillation response, excellent energy resolution, low cost, and good stability—has remained a daunting challenge. Commercial scintillators such as NaI:Tl and CsI:Tl offer high light output but suffer from limited scintillation response, while high-performance alternatives such as LaBr3:Ce are expensive and hygroscopic. Copper-based halide Cs3Cu2I5 has recently attracted intense interest due to its high photoluminescence quantum yield, large Stokes shift, and good air stability. However, the critical question has been how to manufacture these materials reliably and affordably at scale.

The answer lies in the growth method itself. Conventional melt-based techniques such as the Bridgman method require ultrahigh-purity starting materials, high-temperature furnaces, and precise atmosphere control, driving up costs and limiting crystal quality. In contrast, the aqueous-solution method developed by Yao et al. operates at mild temperatures (60°C–70°C) using inexpensive, commercially available reagents. The key innovation is the solvent system: a mixed solution of hydroiodic acid and hypophosphorous acid (HI:H3PO2 = 4:1) creates a strongly reducing environment that prevents oxidation of Cu+ and I−, a persistent challenge in copper halide crystal growth. Additionally, the growth apparatus employs controlled rotation (60 rpm during dissolution, with rotation maintained during the slow cooling period) to ensure homogeneous mixing and uniform temperature distribution. This well-designed chemical system, combined with mechanical agitation, enables the reproducible growth of large-size (up to 10 × 10 × 20 mm3), transparent single crystals with superior structural quality.