Design principle of all-inorganic halide perovskite-related nanocrystals

Abstract

All-inorganic halide perovskite (AIHP)-related (e.g., CsPbBr₃, Cs₄PbBr₆, and CsPb₂Br₅) nanocrystals have attracted great research interest in the recent three years, owing to their unique optical properties. However, rational structural and compositional control of these nanocrystals is still challenging, particularly using the room temperature saturated recrystallization (RTSR) method. Here, we revealed that the structure and the composition of the nanocrystals fabricated by the RTSR approach are highly dependent not only on the previously thought concentration ratio of PbBr₂ and CsBr in N-dimethylformamide (DMF), but the previously neglected absolute concentration and reaction time. This is the reason why pure AIHP-related nanocrystals are usually difficult to prepare using the RTSR method. Through a series of carefully designed experiments, we obtained the evolution trend of the precipitation rate of PbBr₂ and CsBr within a wide concentration range in DMF. Based on the understanding of the growth mechanism, we achieved preparation of pure or a mixture of CsPbBr₃, Cs₄PbBr₆, and CsPb₂Br₅ nanocrystals through either control of the concentration of PbBr₂ and CsBr or the reaction time. This study deepens our understanding of the growth mechanism of AIHP-related nanocrystals, paving the way for future engineering of nanocrystals with desired structures and compositions. These structures with desired compositions will definitely have promising applications in optical and optoelectronic devices.