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.