Atomistic Structures and Energetics of Perovskite Nucleation Pathway During Sequential Deposition Process

Organometal halide perovskite materials are one of the promising candidates for next generation solar energy conversion and optoelectronics applications. Controlling perovskite film morphologies is the key toward promoting device performance, and the sequential deposition method has been extensively used for fabricating high quality perovskite films. Nevertheless, the conversion processes of perovskite from $$\text {PbI}_{2}$$ and methylammonium iodide (MAI) precursor remains unclear. In this study, we investigated the nucleation pathway as well as barriers by performing a series of density functional theory (DFT) calculations. DFT calculations suggested that MAI intercalation allows fluctuation in the lateral dimensions between $$\text {PbI}_{2}$$ layers, which facilitates nucleation of perovskite nuclei with crystalline orientations complied with recent experiments. By computing perovskite nucleus formation energies with different nucleus sizes, we found that the formation of perovskite nuclei must overcome a nucleation barrier for further growth. The perovskite nucleation barriers are sensitive to both MAI intercalation concentration and perovskite nuclei densities. High MAI intercalation concentration yields high nucleation barriers, and this can be mitigated by forming perovskite films with fine perovskite grains, which is consistent with experimental observations. The present study therefore reveals the atomistic structures of perovskite nuclei embedded in MAI-intercalated $$\text {PbI}_{2}$$ , and provides insights into the conversion pathway of perovskite from sequential deposition processes.