Facile surfactant-free microwave-assisted solvothermal synthesis of Cu2Te1−S with enhanced thermoelectric performance

Cu2Te-based compounds show promise for thermoelectric applications, but their synthesis typically involves ball milling or melting-annealing processes. Here, we present a surfactant-free microwave-assisted solvothermal method for the controlled synthesis of Cu2Te1−xSx (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) nanostructures at 503 K within just 30 minutes. The substitution of sulfur promotes the formation of a hexagonal structure in Cu2Te1−xSx with x of 0.2 – 0.5, and inhibits phase transitions during heating. Moreover, the alloying of sulfur contributes to a reduction in hole concentrations toward the optimal range, resulting in enhanced power factors (e.g., 910 μW m−1 K−2 at 825 K for Cu2Te0.9S0.1) and reduced thermal conductivity (e.g., 0.53 W m−1 K−1 at 825 K for Cu2Te0.5S0.5). Ultimately, Cu2Te0.5S0.5 achieves a maximum dimensionless figure of merit of 0.80 at 825 K. This study offers a controllable solution-based strategy for synthesizing Cu2Te-based materials with tunable compositions and enhanced thermoelectric performance.