Growth and Optical Properties of Cs₃Cu₂Br₅ Single Crystals by Vertical Bridgman Method

Abstract In recent years, Copper(I)‐based inorganic halides have garnered significant interest for their exceptional optical properties. In this paper, Cs 3 Cu 2 Br 5 single crystals are grown by the vertical Bridgman method, resulting in large transparent single crystals ≈40 mm in length. The crystals are characterized by X‐ray diffraction (XRD) and differential thermal analysis (DTA). Transmission spectra, photoluminescence (PL), temperature‐dependent fluorescence spectra, X‐ray excitation spectra, and photoluminescence decay time are also measured. The results indicate that the Cs 3 Cu 2 Br 5 single crystal exhibits good optical transmittance of 85% in the wavelength range of 250–800 nm and a large direct bandgap of 3.85 eV. The Cs 3 Cu 2 Br 5 single crystal displays intense broadband blue luminescence, featuring significant Stokes shifts, a microsecond‐long fluorescence lifetime decay, and higher quantum yield, all attributed to self‐trapped exciton emission. The temperature‐dependent fluorescence spectra of the crystals are measured to analyze the luminescence mechanism. In summary, the research indicates that the Cs 3 Cu 2 Br 5 single crystal has certain potential applications in the field of photodetectors, light‐emitting diodes, scintillators, etc.