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 (PbI2) nanowires with van der Waals layered crystal structure and subsequent vapor-phase conversion into methylammonium lead iodide (CH3NH3PbI3) perovskites. Our systematic microscopic investigations confirmed that the VLS-grown PbI2 nanowires display two major growth orientations of [0001] and [1 over bar 21 over bar 0], corresponding to the stacking configurations of PbI2 layers to the nanowire axis (transverse for [0001] vs. parallel for [1 over bar 21 over bar 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 [1 over bar 21 over bar 0] nanowires with an evenly distributed degree of conversion. An ab initio energy calculation suggests that CH3NH3I preferentially diffuses and intercalates into (112 over bar 0) sidewall facets parallel to the [1 over bar 21 over bar 0] nanowire axis. Our results underscore the ability to control the crystal structures of van der Waals type PbI2 in nanowire via the VLS technique, which is critical for the subsequent conversion process into perovskite nanostructures and corresponding properties.

Automated summary

In this study, we demonstrate the growth of lead iodide nanowires with van der Waals layered crystal structure using Sn-assisted VLS, followed by conversion into methylammonium lead iodide perovskites. The VLS-grown PbI2 nanowires showed two major growth orientations and differences in sidewall morphologies were correlated with perovskite conversion. The ability to control crystal structures of PbI2 nanowires via VLS technique is critical for the subsequent conversion process into perovskite nanostructures.