Hyewon Shim1, Yunjeong Hwang2, Sung Gu Kang3, Naechul Shin1,2. 1. Department of Chemical Engineering, Inha University, Incheon 22212, Korea. 2. Program in Biomedical Science & Engineering, Inha University, Incheon 22212, Korea. 3. School of Chemical Engineering, University of Ulsan, Ulsan 44610, Korea.
Abstract
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¯21¯0], corresponding to the stacking configurations of PbI2 layers to the nanowire axis (transverse for [0001] vs. parallel for [1¯21¯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¯21¯0] nanowires with an evenly distributed degree of conversion. An ab initio energy calculation suggests that CH3NH3I preferentially diffuses and intercalates into (112¯0) sidewall facets parallel to the [1¯21¯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.
In thn class="Chemical">is 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¯21¯0], corresponding to the stacking configurations of PbI2 layers to the nanowire axis (transverse for [0001] vs. parallel for [1¯21¯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¯21¯0] nanowires with an evenly distributed degree of conversion. An ab initio energy calculation suggests that CH3NH3I preferentially diffuses and intercalates into (112¯0) sidewall facets parallel to the [1¯21¯0] nanowire axis. Our results underscore the ability to control the crystal structures of van der Waals type PbI2in nanowire via the VLS technique, which is critical for the subsequent conversion process into perovskite nanostructures and corresponding properties.
Authors: Lucas Güniat; Sara Martí-Sánchez; Oscar Garcia; Mégane Boscardin; David Vindice; Nicolas Tappy; Martin Friedl; Wonjong Kim; Mahdi Zamani; Luca Francaviglia; Akshay Balgarkashi; Jean-Baptiste Leran; Jordi Arbiol; Anna Fontcuberta I Morral Journal: ACS Nano Date: 2019-05-03 Impact factor: 15.881