Thermal transport in thermoelectric materials of SnSSe and SnS[formula omitted]: A non-equilibrium Monte-Carlo simulation of Boltzmann transport equation

Abstract

In the present work, thermal transport and the energy conversation in two thermoelectrically efficient candidates of Janus SnSSe and SnS2 are investigated within the non-equilibrium Monte Carlo simulation of the phonon Boltzmann equation. The phonon analysis has been performed to determine the contributed phonon in heat transport. The results present that the dominant participating phonons are the ones from the longitudinal acoustic (LA) branch while the least belongs to the transverse acoustic (TA) modes. Both materials reached the very high maximum temperature in response to the implied wasted heat. This is attributed to the low presence of the critical TA phonons which are on one hand fast enough to leave the hotspot but on the other hand have frequencies commensurable to ZA phonons’ frequency. Also, the temperature profile achieved during the heating and cooling of the materials is studied. It is obtained that the heat propagation through the SnS2 is, at first, swifter, which results in a temperature gradient through the whole material which is less than that of the SnSSe. As the time passes, the heat transfer that is directly related to the material thermal conductivity, slows down. So, the behavior of the SnS2 and SnSSe, in case of the heat propagation status, becomes similar. Moreover, the behavior of the thermoelectric figure of merit (zT), the efficiency (η), and the generated voltage have been figured out. It is stated that the higher zT and η do not guarantee a larger generated Seebeck voltage. This is true, while the generated Seebeck voltage is related to the temperature difference between the heated and the cold junction. Accordingly, how far the temperature of matter rises in response to the implied wasted heat is directly related to the obtained voltage. Mainly, it is presented that the maximum temperature that a material achieves, alongside the temperature gradient and the material property Seebeck coefficient, are essential in introducing thermoelectrically efficient materials with reasonable thermal to electrical energy conversion, useful for thermal engineering.