Thermal transport in thermoelectric materials of SnSSe and SnS${}_2$: a non-equilibrium Monte-Carlo simulation of Boltzmann transport equation

Abstract

In the present work, thermal transport and energy conversation in two thermoelectrically efficient candidates of Janus SnSSe and SnS${}_2$ are investigated within the non-equilibrium Monte Carlo simulation of phonon Boltzmann equation. The phonon analysis is performed to determine the contributed phonons in heat transport. The results present that the dominant participating phonons are longitudinal acoustic ones while the least belongs to the transverse acoustic (TA) mode. 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. Also, the temperature profile achieved during the heating and cooling of the materials is studied. It is obtained that the heat propagation through the SnS${}_2$ 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 SnS${}_2$ and SnSSe, in case of the heat propagation status, becomes similar. More, the behavior of the thermoelectric figure of merit (zT), the efficiency ($\eta$), and the generated voltage have been figured out. It is stated that the higher zT and $\eta$ 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 related to the obtained voltage. Mainly, it is presented that the maximum temperature that a material achieves, alongside the temperature gradient and material property Seebeck coefficient, are essential in introducing thermoelectrically efficient materials with reasonable thermal to electrical energy conversion.

9 pages, 9 figures