Enhancement in the Thermoelectric Performance of SnS Monolayer by Strain Engineering

Nanostructuring is one of the well-known tools for improving the thermoelectric figure of merit, but it has limits when tuning the lattice thermal conductivity. The thermoelectric coefficients, including the lattice thermal conductivity in two-dimensional materials, can further be modified using strain engineering, which manipulates the interatomic forces and the energy levels in these systems. With this in mind, we investigate the thermoelectric properties of the SnS monolayer under uniaxial compressive and tensile strains using first-principles calculations and the Boltzmann transport equation. Analysis of the elastic constants and Poisson ratio points toward the applicability of strain only along the armchair or b direction. Systems with uniaxial compressible and tensile strains from −4% to 5% along the armchair direction are found to be dynamically stable. A high power factor of ∼1.1 W m –1 K –2, which is ∼1.8 times higher than the unstrained case, is predicted for the 1% strain case for p-type carriers. A ∼77% enhancement in the dimensionless figure of merit ( ZT ) for p-type carriers and ∼86% enhancement in the figure of merit for n-type carriers with respect to equilibrium is detected upon application of a minimal 1% tensile strain. An almost 3-fold increase in ZT can be achieved for 1% strain at 600 K. This enhancement in ZT renders the strained monolayer a much more promising candidate for thermoelectric applications.