Luminescence and scintillation of Cs3Cu2I5:Tl and Cs3Cu2I5:Ag scintillators

The inorganic scintillation crystal, Cs₃Cu₂I₅, has garnered considerable interest from the nanocrystal, thin film, and bulk crystal communities. Its non-toxic composition, cost-effectiveness, air stability, good light yield, high density, reasonable decay time, and visible wavelength compatibility with several photodetectors make the bulk Cs₃Cu₂I₅ crystal a promising candidate for a wide range of applications, including optoelectronics, x-ray and γ-ray radiation detection. Further studies reveal a low-dimensional metal halide structure with a suggested self-trapped exciton and complex trap processes. This implies that there is potential for further research into the luminescence and scintillation of this crystal to optimize its performance. Based on the self-trapped exciton mechanism with the goal of room-temperature application, activated scintillation has been considered. The monovalent activation center could be a good candidate for study. Following the same concept in well-known CsI crystals, the Cs₃Cu₂I₅:Tl and Cs₃Cu₂I₅:Ag crystals were studied in this work. These crystals were synthesized and grown using the Bridgman technique. The good parts of the crystal were cut and polished. The scintillation characteristics were measured using the Hamamatsu R6233-100 photomultiplier tube (PMT) with emission wavelengths well-matched to these crystals. Data acquisition and analysis were performed using a 500-MHz flash analog-to-digital converter (Notice, Korea) with a CERN ROOT-based program. The absolute light yield was measured using the PMT single photoelectron technique. The pulse shape study, including decay time and particle discrimination, was investigated for γ rays and α particles. The charge comparison method with optimization was used for pulse shape discrimination. Our results showed the potential application not only for x-ray and γ-ray measurements but also for α measurements. However, the unexpected inverse performance of these activation centers was observed, leading to the motivation for luminescence investigation. This work compared the x-ray luminescence of these doped crystals to other related crystals. For this purpose, CsI, CsI:Cu, CsI:Ag, and intrinsic Cs₃Cu₂I₅ crystals were grown. It suggests a complex energy transfer to the Tl⁺ and Ag⁺ activation centers regarding the Cu⁺ ion in the electronic structure. Our study indicates that these crystals have the potential to be effective scintillators for room-temperature applications. These applications include radiation detection and measurement (x-rays, γ rays, and α particles), radiography (such as medical imaging and defect inspection), and rare event searches as promising candidates for dark matter search.