Thermoelectric properties of the novel cubic structured silicon monochalcogenides: A first-principles study

The low-cost and non-toxic candidates of the Group-IV monochalcogenide family have attracted significant attention in recent years for large-scale thermoelectric applications. We conduct comprehensive investigations of the thermoelectric response of relatively inexpensive and less toxic cubic structured Si-monochalcogenides (pi-SiS, pi-SiSe, and pi-SiTe) for renewable energy applications. The full-potential linearized-augmented-plus-local-orbital method within density functional theory has been adopted to calculate the ground state energies, whereas the semi-classical Boltzmann transport theory has been used for the calculations of thermoelectric properties. The Si-monochalcogenides in cubic phase demonstrate large values of thermopowers that amounts to 1740.0 mu V/K, 1405.0 mu V/K, and 771.92 mu V/K of the pi-SiS, pi-SiSe, and pi-SiTe respectively at 300 K. The thermopowers show an insignificant response to increase in temperature which is beneficial for the high-temperature thermoelectric applications of these materials. The optimal values of thermoelectric power factors of the cubic structured Si-chalcogenides occur at attainable doping levels and have been originated from the joint contribution of moderate electrical conductivities and thermopowers. These materials demonstrate the figure of merit values approaching unity and have shown a trivial response to the temperature gradient. Moreover, the occurrence of the optimal values of thermoelectric coefficients for electrons doped regime suggests the n-type doping as an easy option for enhancing the thermoelectric performance of these materials. Our investigations show that the Si-monochalcogenides in cubic phase feature interesting thermoelectric performance and can be used as a suitable replacement for the toxic and expensive binary chalcogenides for thermoelectric applications. (C) 2018 Elsevier B.V. All rights reserved.