Synthesis of all-inorganic CsPb2Br5 perovskite and determination of its luminescence mechanism

Abstract

All-inorganic cesium lead halide perovskite materials, such as CsPbBr₃ and CsPb₂Br₅, have drawn immense attention recently due to their potential applications in optoelectronics. However, unlike the extensively-studied CsPbBr₃, many of the fundamental properties of CsPb₂Br₅ remain unclear, such as its electronic structure and photoluminescence (PL) mechanism. In this work, we developed a novel environmentally friendly chemical method to synthesize CsPb₂Br₅, where only water and ethanol were used as solvents. The optical property and electronic structure of CsPb₂Br₅ were then examined both experimentally and theoretically. For the first time we found that the band-edge emission of CsPb₂Br₅ was not in the visible range as reported in the literature but rather located in the ultraviolet range. By monitoring the PL property during phase conversion between CsPb₂Br₅ and CsPbBr₃, we propose that previously-reported visible emission might be due to the involvement of CsPbBr₃ during sample preparation. Overall, this study presents a novel green method for the preparation of CsPb₂Br₅ and clarifies the optical properties and electronic structure of CsPb₂Br₅.