Strain-induced high thermoelectric performance of monolayer SnSe: a DFT study

Abstract Thermoelectric (TE) properties of monolayer tin selenide (SnSe) in the Pnma and Cmcm phases are investigated using density functional theory and semi-classical Boltzmann transport theory. The influence of uniaxial and biaxial strain on the electronic structure and transport properties is analyzed, with particular focus on symmetry preservation and valley convergence. Applying 5% biaxial compressive strain to the Cmcm phase enhances valley degeneracy and electronic transport, resulting in a figure-of-merit ( ZT ) reaching ∼4.61 at 900 K. In contrast, the Pnma phase exhibits relatively minor changes in thermoelectric performance under the same strain conditions. These results demonstrate that strain engineering can be an effective strategy to improve the thermoelectric efficiency of monolayer SnSe, particularly in the high-symmetry Cmcm phase.