Thermoelectric performance of Cu3InSnSe5 and MnSe pseudo-binary solid solution

• MnSe alloying results in a multiband valley feature and a downward shift of the fermi level. • Nanoscale MnSe 2 precipitates effectively scatter low-frequency phonons in the mid-to-low temperature range. • The 10 mol.% MnSe alloyed Cu 3 InSnSe 5 pseudo-binary solid solution achieves an outstanding average ZT of 0.50 over the 300–773 k temperature range and a peak ZT of 1.00. • The solution-strengthening effect of MnSe and the multi-scale distribution of MnSe 2 precipitates enhances the vickers hardness of Cu 3 InSnSe 5 to 300HV. Cu 3 InSnSe 5 is a newly discovered copper-based diamond-like thermoelectric semiconductor, whose thermoelectric performance can be further enhanced by the MnSe alloying herein. We observed the formation of MnSe 2 precipitates that effectively scattered low-frequency phonons, which significantly reduced the lattice thermal conductivity at mid-to-low temperatures. While a high amount of MnSe alloying led to the formation of MnSe 2 precipitates which enhanced the phonons scattering, a smaller MnSe content improved the power factor in a certain as well. Ultimately, our research achieved a peak ZT of 1.00 and an average ZT of 0.50 over the 300–773 K temperature range by 10 mol.% MnSe alloyed Cu 3 InSnSe 5 pseudo-binary solid solution, demonstrating the potential of MnSe alloying for optimizing the thermoelectric performance of copper-based diamond-like semiconductor materials.