First-principles study of thermoelectric transport properties in low-buckled monolayer silicene

In this paper, we investigate the thermoelectric transport coefficients namely the Seebeck coefficient, the electrical conductivity, the electronic thermal conductivity and the lattice thermal conductivity using firstprinciples calculations in density functional theory. We also estimate the figure-of-merit for both intrinsic as well as extrinsic low-buckled monolayer silicene. Using Electron-Phonon Wannier function, we calculate the average scattering time in the reduced Brillouin zone as a function of temperature. The scattering time of electrons in the conduction band is found to be slightly higher than that of holes in the valence band. Also, the out-of-plane acoustic phonon modes scatter more strongly than the in-pane acoustic modes and hence contributes less in lattice thermal conductivity. We observe that the lattice thermal conductivity of monolayer intrinsic silicene comes out of the order of 9.2 W-1 K-1 and the figure-of-merit in n-type material is almost twice to that of the p-type at around 1200 K. We compare the results obtained with HSE06 hybrid functional and PBE functional and find that there is a significant improvement in the values of those transport coefficients calculated using HSE06.