Enhanced thermoelectric performance of CoSbS via Se doping at dual Sb and S sites

The natural mineral-based CoSbS compound has been identified as a potential candidate material for thermoelectric power generation. In this report, the solid solutions of CoSb _1−xS _1−xSe _2x (x ≤ 0.2) were constructed, and their electrical and thermal properties were studied at the temperatures ranging from 323 to 823 K. The results show that the dual doping of Se on Sb and S sites not only tunes the carrier concentration but also modifies the electronic structure, thereby optimizing the power factor of CoSbS effectively. Meanwhile, both the mass and the strain field fluctuation caused by the substitution of Se for both Sb and S strongly suppress the thermal conductivity of CoSbS, and finally make an enhanced zT∼0.3 for CoSb _0.8S _0.8Se _0.4 at 823 K. In particular, the maximum averaged zT from 323 to 823 K in this study reaches ∼0.2, far exceeding the results of Se doping at single Sb or S site in CoSbS. These results indicate that dual doping at Sb and S sites via Se is an effective approach to make better thermoelectric performance for CoSbS.