Enhanced γ-Ray Detection Performance of Cs3Cu2I5 Single Crystals via Suppression of Second-Phase Formation
Single-crystalline Cs3Cu2I5 has attracted considerable interest owing to its excellent scintillation performance and favorable stability. Nevertheless, second phases induced by peritectic reactions during melt growth give rise to deteriorated scintillation properties and promote crystal cracking. In this work, the effects of non-stoichiometric ratios of raw material (n(CsI)=0.57, 0.62, and 0.63) on the crystallization behavior and scintillation properties were systematically investigated. The results show that the crystal quality is optimal at n(CsI)=0.62, featuring high transparency, absence of macroscopic inclusions, and cracking free, with a PLQY of 79.3%. Temperature-dependent photoluminescence verifies the self-trapped exciton emission mechanism with strong exciton-phonon coupling, giving an exciton binding energy of 473.9 meV and a Huang-Rhys factor S of 79.8. The as-grown crystal exhibits an optimized light yield of 24,380 photons/MeV, an energy resolution of 3.8% for 137Cs (662 keV) γ-rays, a dominant decay time of 957 ns, and excellent linear response in the medium-to-high energy region. Precise regulation of the raw material stoichiometry can effectively suppress the formation of second phases, yielding high-quality Cs3Cu2I5 single crystals whose comprehensive performance demonstrates promising application potential in γ-ray detection.