Cryogenic Scintillation Properties of Lead-Free Cs₃Cu₂I₅ Single Crystals

Perovskite scintillators have become increasingly popular in recent years because of their simple production and high sensitivity to X-ray. Due to large Stokes shifts, high light yield, eco-friendly fabrication, and good stability, the lead-free Cu-based perovskites have gained much attention. In this paper, we prepared the Cs₃Cu₂I₅ single crystals (SCs) by the solution-processed method. At room temperature, we measured the emission band at 440 nm with an average decay time of 595 ns under X-ray excitation. Under ¹³⁷Cs γ-ray excitation, we determined that the light yield of Cs₃Cu₂I₅ SCs was 23 000 photons/MeV. Notably, under alpha particle excitation by ²⁴¹Am, the light yield of Cs₃Cu₂I₅ SCs is approximately 3.2 times higher than that of the commercial scintillator LYSO(Ce). In addition, we systematically investigated the cryogenic scintillation properties of Cs₃Cu₂I₅ SCs at the temperature range of 60-300 K. With decreasing temperature, the intensity of the emission band at 440 nm significantly increases, and an additional emission band at 336 nm emerges below 100 K. Meanwhile, the temperature-dependent decay times were determined. The fast and slow decay time of Cs₃Cu₂I₅ SCs are estimated to be 221 and 1193 ns, respectively, at 60 K. Our findings highlight the great potential for Cs₃Cu₂I₅ SCs to be a cryogenic scintillator.