Reverse Temperature Solution to Grow High-Quality CsCu2I3 Single Crystal with Formic Acid for Radiation Detection

One-dimensional (1D) CsCu2I3 single crystals (SCs) have been investigated as novel sensitive X-ray and γ-ray scintillators, which can be prepared by the Bridgman method and solution method. However, to date, no research team has studied the scintillation performance of CsCu2I3 single crystals grown using the solution method, and traditionally grown single crystals using the antisolvent method are of poor quality and small sizes. In this work, high-quality CsCu2I3 SC was synthesized with formic acid as an additive by using the inverse temperature crystallization solution method, and its optical properties and scintillation performance were measured. The experimental results indicate that the addition of formic acid can stabilize the growth of crystals in solution, and the selected solvent DMF is beneficial for the growth of rod-like single crystals instead of needle-like single crystals by the DMSO. The experiment resulted in high-quality CsCu2I3 single crystals reaching a length of 13 mm, with no visible inclusions in the crystal. The full width at half-maximum (fwhm) of the X-ray rocking curve was 0.028°, indicating its high crystalline quality. It exhibits stability in air and emits bright yellow light under ultraviolet irradiation. The CsCu2I3 SC shows a much shorter PL decay of 118 ns and afterglow of 0.01% @ 12 ms compared to commercial CsI: Tl single crystal. The light yield of CsCu2I3 SC is 21800 photons/MeV, showing great potential as a scintillation material.