Monodisperse Lead-Free Perovskite Cs₃Cu₂I₅Nanocrystals: Role of the Metal Halide Additive

Lead-free copper-based perovskite Cs3Cu2X5 nanocrystals (NCs) have attracted a great deal of attention as novel active materials in optoelectronic devices because of their high emission stability, unique self-trap exciton emission, and high quantum yield, as well as their relatively low toxicity and earth-abundant constituents. On the contrary, despite the widespread interest in Cs3Cu2X5 bulk or thin-film structures, the synthesis of highly crystalline and uniform Cs3Cu2X5 NCs in high yield has rarely been reported on the basis of the conventional growth kinetics because of our insufficient understanding of their formation mechanism. We report a strategy for increasing the yield and controlling the size of Cs3Cu2X5 NCs by utilizing the metal halide additive to adjust the thermodynamic equilibrium and chemical potential. Monodisperse Cs3Cu2I5 nanocubes with a photoluminescence quantum yield of 72.4% could be obtained because of the unique properties of MnI2, which can form multiple ionic salts and promote the reaction of CuI with a ligand to form Cu oleate-rich conditions for the assembly of NCs. Therefore, the metal halide additive plays a critical role in increasing the synthesis yield and controlling the size of copper-based Cs3Cu2I5 NCs based on precise mechanistic studies.