VLS Homoepitaxy of Lead Iodide Nanowires for Hybrid Perovskite Conversion

Controlled fabrication of lead halide-based perovskite (LHP) nanostructures provides a new methodology for exploiting the excellent optoelectronic properties of the material. Here, we report the vapor-liquid-solid (VLS) growth of a highly uniform and dense array of [0001]-oriented PbI₂ nanowires using PbI₂ thin film as the epitaxial substrate layer. We show that reducing the lattice mismatch of the van Der Waals epitaxial PbI₂ substrate layer is necessary to accommodate the aligned nanowire growth. Our proposed layer growth model suggests that the nanowire growth is stabilized by maintaining the {0001} liquid-solid interface, which stems from the nucleation on the PbI₂ substrate layer. We also demonstrate that the strain-induced nanowire deflection after conversion into CH₃NH₃PbI₃ depends on the transfer sequence and conversion time. These findings provide a general opportunity to design and fabricate nanostructures, such as heterojunctions or superstructures for future device applications, rationally based on lead halide or LHP nanowires.