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Enhancement of the thermoelectric properties of MnSb2Se4 through Cu resonant doping

MnSb2Se4 is a narrow band semiconductor having large Seebeck coefficients and intrinsically low thermal conductivities, but modest thermoelectric zT values due to having low carrier concentrations and high electrical resistivity. Here, we report that Cu substituted Mn1−xCuxSb2Se4 (0 ≤ x ≤ 0.35) materials display resonant doping behavior, leading to significantly enhanced power factors (PFs) and overall thermoelectric zT values in the measured temperature range. For the optimized composition Mn0.75Cu0.25Sb2Se4, the PF reaches 0.26 mW m−1 K−2 at 773 K, coupled with low thermal conductivities of 0.61 W K−1 m−1 to 0.32 W K−1 m−1 over the measured temperature range. A peak zT of 0.64 at 773 K is achieved, which is a 100% increase in comparison to undoped MnSb2Se4. Such a high zT has rarely been seen in thermoelectric materials with a low symmetry of crystallization, implying that Cu-doped MnSb2Se4 could be considered as a new platform in thermoelectric research for intermediate temperature power generation.