Routes to High-Carrier-Density Doping in Thermoelectric SnSe

Abstract

Ultralow thermal conductivity and distinct transportation properties of SnSe have attracted lots of interest in optimizing its thermoelectric properties. In this work, an extensive defects study of layered SnSe semiconductors was carried out using density functional theory (DFT) calculations. Results show that intrinsic SnSe is a p-type semiconductor under Sn-poor conditions because of the Sn vacancy and is slightly n-type under Sn-rich conditions. For extrinsic defects, doping effects of numerous elements, such as alkali metals, transition metals (Cu, Ag, and Au), boron and nitrogen group elements, and halogen elements on carrier densities are studied. In our calculations, ternary phases are included in the phase diagram analysis to improve the accuracy of SnSe dopability prediction. We found that Na exhibits extraordinary p-type doping efficiency with the hole concentration improved by around two orders of magnitude. Cl and Br enhance the electron concentration by four orders of magnitude, indicating they are promising n-type doping candidates.