Strain-induced enhancement in the electronic and thermal transport properties of Tin Sulphide bilayer

The enhancement in the thermoelectric figure of merit (ZT) of a material is limited by the interplay of the electronic transport coefficients. Here we report the greatly enhanced thermoelectric performance of SnS bilayer with the application of isotropic strain, due to the simultaneous increase in Seebeck coefficient and low lattice thermal conductivities. Based on first-principles calculations combined with Boltzmann transport theory, we predict that the band structure of the SnS bilayer can be effectively tuned by the strain, and the Seebeck coefficient is significantly improved for the tensile strain. The lattice thermal conductivities for the bilayer under the tensile strain are quite low (0.21-1.89 Wm^{−1}K^{−1} at 300 K) due to the smaller frequencies of the acoustic phonon modes. Along the zigzag (armchair) direction, the room temperature peak ZT value of 4.96 (2.40) is obtained at a strain of 2% (4%) which is 5.3 (2.03) times higher than the peak ZT of unstrained bilayer along the zigzag (armchair) direction. Thus the strain-tuned SnS bilayer is a good thermoelectric material with low lattice thermal conductivities and promising ZT values at room temperature.