Revealing Cation-Exchange-Induced Phase Transformations in Multielemental Chalcogenide Nanoparticles

To control the process of cation exchange (CE) in a multielemental system, a detailed understanding of structural changes at the microscopic level is imperative. However, the synthesis of a multielemental system has so far relied on the CE phenomenon of a binary system, which does not necessarily extend to the higher-order systems. Here, direct experimental evidence supported by theoretical calculations reveals a growth model of binary Cu–S to ternary Cu–Sn–S to quaternary Cu–Zn–Sn–S, which shows that cations preferentially diffuse along a specific lattice plane with the preservation of sulfuric anionic framework. In addition, we also discover that, unlike the commonly accepted structure (P63mc), the metastable crystal structure of Cu–Zn–Sn–S phase possesses fixed Sn occupancy sites. By revealing the preferential nature of cations diffusion and growth mechanism, our work provides insight into controlling the stoichiometry and phase purity of novel multielemental materials. Ministry of Education (MOE) National Research Foundation (NRF) Accepted version We acknowledge financial support from National Research Foundation (NRF), Singapore, through the Singapore-Berkeley Research Initiative for Sustainable Energy (SinBeRISE) and Nanomaterials for Energy and Water Management (SHARE NEW) CREATE program. L.H.W. thanks the funding support from Singapore Ministry of Education, Tier 2 (2016-T2-1-030). S.L. acknowledges the funding support from Singapore Ministry of Education Tier 1 (107/15). H.Z. thanks the funding support from U.S. DOE BES Materials Sciences and Engineering Division Under Contract No. KC22ZH. X.Y.L. thanks the funding support from Singapore Ministry of Education, Tier 1 (RG21/16) and Tier 2 (MOE2016-T2-1- 043) grants.. The work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. We thank Fiona Doyle for lending us her synthetic laboratory in University of California Berkeley (UCB), Song Chengyu and Karen Bustilo for their help and assistance on TEM, and Matthew P. Sherburne for nanoparticle growth discussion.