Extremely Anisotropic Thermoelectric Properties of SnSe Under Pressure

SnSe has attracted extensive attention due to its ultralow thermal conductivity and excellent thermoelectric properties. In this work, pressure‐induced thermoelectric properties of Pnma SnSe are investigated via first‐principles calculations. We uncover distinct energy isosurfaces topology transition of conduction band by applying pressure. The newly created conduction band valley caused by pressure has a distinct anisotropic shape compared to the old one. Inducing pressure can greatly enhance the anisotropy of electronic transport properties of the n‐type Pnma SnSe. Furthermore, the lattice thermal conductivity also exhibits anisotropic behavior under pressure due to a special collaged phonon mode. The pressure‐induced lattice thermal conductivity along the a‐axis shows a slower growth trend than that along the b‐axis and c‐axis. The optimal ZT value of the n‐type Pnma SnSe along the a‐axis can reach 1.64 at room temperature. These results would be helpful for designing the Pnma SnSe‐based materials for the potential thermoelectric and valleytronic applications.