Orientation-Dependent Conversion of VLS-Grown Lead Iodide Nanowires into Organic-Inorganic Hybrid Perovskites

In this study, we demonstrate Sn-assisted vapor-liquid-solid (VLS) growth of lead iodide (PbI(2)) nanowires with van der Waals layered crystal structure and subsequent vapor-phase conversion into methylammonium lead iodide (CH(3)NH(3)PbI(3)) perovskites. Our systematic microscopic investigations confirmed that the VLS-grown PbI(2) nanowires display two major growth orientations of [0001] and [[Formula: see text] 2 [Formula: see text] 0], corresponding to the stacking configurations of PbI(2) layers to the nanowire axis (transverse for [0001] vs. parallel for [[Formula: see text] 2 [Formula: see text] 0]). The resulting difference in the sidewall morphologies was correlated with the perovskite conversion, where [0001] nanowires showed strong localized conversion at top and bottom, as opposed to [[Formula: see text] 2 [Formula: see text] 0] nanowires with an evenly distributed degree of conversion. An ab initio energy calculation suggests that CH(3)NH(3)I preferentially diffuses and intercalates into ([Formula: see text]) sidewall facets parallel to the [[Formula: see text] 2 [Formula: see text] 0] nanowire axis. Our results underscore the ability to control the crystal structures of van der Waals type PbI(2) in nanowire via the VLS technique, which is critical for the subsequent conversion process into perovskite nanostructures and corresponding properties.