Deterministic Synthesis of a Two-Dimensional MAPbI₃ Nanosheet and Twisted Structure with Moiré Superlattice

The synthesis of extremely thin 2D halide perovskites and the exploration of their interlayer interactions have garnered significant attention in current research. A recent advancement we have made involves the development of a successful technique for generating ultrathin MAPbI₃ nanosheets with controlled thickness and an exposed intrinsic surface. This innovative method relies on utilizing the Ruddlesden-Popper (RP) phase perovskite (BA₂MA_<i>n</i>-1Pb_<i>n</i>I_3<i>n</i>+1) as a template. However, the precise reaction mechanism remains incompletely understood. In this work, we systematically examined the dynamic evolution of the phase conversion process, with a specific focus on the influence of inorganic slab (composed of [PbI₆]^4- octahedrons) numbers on regulating the thickness and quality of the resulting MAPbI₃ nanosheets. Additionally, the atomic structure is directly visualized using the transmission electron microscopy (TEM) method, confirming its exceptional quality. To illustrate interfacial interactions in ultrathin structures, artificial moiré superlattices are constructed through a physical transfer approach, revealing multiple localized high-symmetry stacks within a distinctive square moiré pattern. These findings establish a novel framework for investigating the physics of interfacial interactions in ionic semiconducting crystals.