Enhanced thermoelectric performance of Cu₃SbS₄ flower-like hierarchical architectures composed of Cl doped nanoflakes via an in situ generated CuS template

In this work, Cu₃SbS₄ hierarchical flower-like microspheres composed of chlorine (Cl^-)-doped Cu₃SbS₄ nanoflakes are realized via a one pot solvothermal ion exchange reaction. The kinetic factors including the duration time, the ratio of source materials, and the KOH concentration, are systematically investigated. Using a suite of analytical techniques, including SEM, XRD and FTIR, the mechanism of the two stage in situ chemical transformation of CuS flower-like microspheres consisting of nanoflake intermediates to the target product Cu₃SbS₄ is elucidated. The difference in solubility between reactants and products (Ksp(CuS) > Ksp(CuSbS_x)) determines that the ion-exchange reaction from transition binary to ternary metal chalcogenides is favorable under the impetus of a thermodynamic driving force. In addition, the optical and enhanced thermoelectric transport properties are investigated. The results revealed that Cl-doped Cu₃SbS₄ exhibited an improved power factor, which was 8 times higher than that of undoped Cu₃SbS₄ at 500 K. The current study not only provides a facile and economical way to synthesize high-quality Cl-doped Cu-Sb-S three dimensional (3D) hierarchical nanostructures, but also opens up a new route for preparation of other I-V-VI multicomponent chalcogenide NCs, such as Cu-Bi-S and Cu-Pb-S systems, which would be difficult to obtain otherwise.