Phase-Controlled Crystal Growth of Cs3Cu2I5 Scintillators via the Solution Method for γ-ray Detection

The zero-dimensional (0D) copper halide perovskite Cs3Cu2I5 exhibits outstanding luminescence and scintillation properties, making it a highly promising scintillator for γ-ray detection. Solution growth is a favorable and inexpensive method for growing Cs3Cu2I5 single crystals; however, scalable growth of Cs3Cu2I5 crystals with low defect density suffers from the unavoidable formation of secondary phase CsCu2I3. In this work, centimeter-size, high quality Cs3Cu2I5 single crystals are synthesized via a constant-temperature solvent evaporation crystallization (CT-SEC) method, in which the formation of CsCu2I3 can be eliminated by precursor engineering. The phase evolution behavior is elucidated as the decrease in the I-/Cu+ concentration ratio during the growth of the Cs3Cu2I5 crystal. Through synergistic regulation of precursor antioxidative treatment and raw material stoichiometry, the long-term phase-stable growth of Cs3Cu2I5 single crystals is achieved. The obtained Cs3Cu2I5 crystals exhibit excellent energy resolutions of 5.38% for 137Cs and 13.30% for 241Am γ-ray irradiation.