Decoding the Mechanisms of Room-Temperature Solid-State Synthesis of Halide Perovskites

Room-temperature solid-state synthesis of halide perovskites is a simple, single-step, efficient, and cost-effective method to synthesize halide perovskite precursors that can be subsequently used to deposit thin films by using various techniques. Solid-state methods also reduce and, in some cases, eliminate additional time-consuming treatments and purification steps. Therefore, understanding the reaction mechanism is crucial to the controlled synthesis of various perovskite systems. This study explores the reaction mechanisms and associated kinetics of room-temperature solid-state halide perovskites synthesized by using a planetary ball-milling system. A CsPbBr₃ system (ABX₃) is used as a reference to study the exchange of A, B, and X sites with methylammonium (MA⁺), Cd²⁺, and Cl^-, respectively. Various characterization techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-vis) spectroscopy, and field emission scanning electron microscopy (FESEM), are used to analyze the resulting materials at different reaction times. The findings highlight the significance of factors such as perovskite formation energy, the particle size distribution of precursors, bond dissociation energy, molecular weight of the A cation, and the size and mobility of the X⁻ ion in influencing the mechanism and kinetics of the reactions. Furthermore, the conversion of precursors to perovskites is investigated using XPS, which provides valuable information on the chemical shifts of the precursors and perovskite materials and can serve as a reliable source for future studies.