A theoretical study of the out-of-plane electrical transport of n-type thermoelectric SnS*

As a promising thermoelectric material containing non-toxic and abundant elements, SnS has attracted significant research focus in recent years. To further improve the thermoelectric energy conversion efficiency of SnS, it is critical to have a thorough understanding of its electronic structure. In this work, we have calculated the band structure of SnS from first principles using the HSE06 hybrid functional to unveil the detailed valence band features. We have then compared the band features of SnS with those of the analogue SnSe, which was recently shown to have a very high thermoelectric figure of merit. By further investigating the doping effects of n-type impurities on the electronic structure and electrical transport properties of SnS, we identify resonant states near the bottom of the conduction band and find a considerable increase of electron delocalization along the out-of-plane direction of the layer crystal structure. Boltzmann transport calculations show that these effects on the electronic structure may result in enhanced electrical transport properties.