Molecular Insights into Early Nuclei and Interfacial Mismatch during Vapor Deposition of Hybrid Perovskites on Titanium Dioxide Substrate

Theoretical understanding of the nucleus structures of hybrid perovskites, such as those of the prototypical methylammonium lead triiodide (MAPbI3), can greatly improve the deposited thin film quality and the resulting optoelectronic device performance. In this paper, we report a systematic molecular dynamics simulation study on nucleation and interfacial mismatch during the vapor deposition of MAPbI3 on the TiO2 substrate under different ionic precursor (PbI2 and MAI salts) compositions and temperatures. Despite significant anisotropic lattice mismatches, small defects are observed at the TiO2/[MAI]0 interface due to intermediate electrostatic attractions between I and Ti atoms, while very strong electrostatic attractions between Pb and O atoms lead to significant defects at the TiO2/[PbI2]0 interface. From the vapor deposition simulations, we identify PbI42– tetrahedra, PbI53– pyramids, and PbI64– octahedra as dominant polyhedral building blocks of early MAPbI3 nuclei. Specifically, the PbI53– pyramids ...