Room-Temperature Grown 1D CsCu₂I₃ and 0D Cs₃Cu₂I₅ Metal Halide Perovskites Single Crystals: Optical and Scintillation Properties

Low-dimensional metal halide perovskites exhibit broad emission, large Stokes shift, and high photoluminescence quantum yield (PLQY) due to strong quantum confinement effects. Among various low-dimensional perovskites, 1D CsCu₂I₃ and 0D Cs₃Cu₂I₅ wide-bandgap perovskite single crystals (SCs) show superior luminescence properties compared to other perovskites of the same class, owing to their excellent air stability, high attenuation coefficients, non-hygroscopic nature, high atomic density, and low-cost solution processability. These features make them suitable for X-ray and γ-ray detection. However, their widespread application is limited by the high growth costs associated with high-temperature furnace-based synthesis. Therefore, developing low-cost solution-based growth routes for scintillating SCs is crucial for realizing affordable medical imaging tools such as X-ray imaging, Computed Tomography (CT), and Digital Radiography (DR).

In this work, 1D CsCu₂I₃ and 0D Cs₃Cu₂I₅ SCs were successfully grown using a room-temperature solvent evaporation method. Comprehensive structural, optical, and scintillation characterizations were performed. The crystalline quality was confirmed by single-crystal X-ray diffraction (XRD). The SCs were coupled to a silicon photomultiplier, and pulse-height spectra were recorded using various γ-ray sources. Energy resolution, light output, and linearity in light output were analyzed. CsCu₂I₃ SC exhibited improved energy resolution compared to previously reported values for crystals grown via melt or conventional solution methods. The measured densities were 5.01 g/cm³ for CsCu₂I₃ and 4.5 g/cm³ for Cs₃Cu₂I₅. Monte Carlo simulations were carried out using the GEANT4 toolkit to estimate photopeak detection efficiencies. The simulated efficiencies for Cs₃Cu₂I₅, CsCu₂I₃, and NaI were compared for crystals of identical dimensions, showing higher efficiency for Cs₃Cu₂I₅ and CsCu₂I₃ compared to commercially available NaI:Tl, thereby extending their potential in high-efficiency detector applications. Additionally, pulse shape discrimination (PSD) studies were conducted.