Li+-Induced Enhancement of Excitonic Luminescence in γ-CuBr Single Crystals Grown by the Vertical Bridgman Method

The intrinsic defects in pure γ-CuBr crystal lead to obvious nonradiative recombination, thereby significantly suppressing its ultrafast free-exciton emission. In this study, we successfully grew undoped and Li+-doped CuBr:x%Li (x = 0, 1, 3, 5) single crystals using the vertical Bridgman method after purifying raw materials via recrystallization. The influence of Li+ ion incorporation on the crystal structure and photoluminescence (PL) properties was investigated. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) confirmed that Li+ is incorporated in the lattice of γ-CuBr. Moderate Li+ doping markedly enhances the near-band-edge (NBE) emission, with CuBr:3%Li composition exhibiting the highest PL intensityapproximately six times that of pure CuBr. Time-resolved PL further demonstrates an ultrafast radiative decay lifetime of 2.40 ns at 419 nm for the optimal crystal. Temperature-dependent photoluminescence (PL) measurements revealed that the thermal stability of NBE emission significantly improved after Li+ doping. The thermal activation energy of CuBr:3%Li is 382.6 meV.