The effects of Zn doping on the thermoelectric performance of Cu12Sb4S13

We used first-principles electronic structure calculations and Boltzmann transport theories to understand the thermoelectric behavior of tetrahedrites. We performed calculations on the Zn substituted derivatives with Zn occupied each lattice site in the parent compound Cu12Sb4S13, to study Zn substitution mechanism, and the relation between Zn substitution site and thermoelectric performance. We found that the most energetically favorable sites for Zn is the Cu(1) sites, and the next is the Cu(2) sites. And the room-temperature Seebeck coefficient of the host was enhanced nearly 255 and 7 times by Zn doping at Cu(1) and Cu(2) sites, owing to the decrease of carrier concentration and the increase of band effective mass, respectively. However, the electrical conductivity showed a marked decrease upon Zn doping at Cu(1) and Cu(2) sites, due to the decrease in carrier contribution and low mobility, respectively. As a result, the Cu12Sb4S13 compounds substituted with Zn at Cu(1) sites have a preferable optimizing power factor at room temperature. The optimizing power factor of the host could get an about 8-time improvement at room temperature upon Zn substituting at Cu(1) sites.