High Thermoelectric Power Conversion Efficiency of an Earth-Abundant Janus Silicon Oxy-Sulfide Monolayer: A First-Principles Study

Abstract

The tunable properties of Janus monolayers, along with advances in their synthesis, make these low-symmetry materials excellent candidates for thermoelectric power generation. In this study, we systematically investigate the electronic and thermal properties of the Janus silicon oxy-sulfide monolayer. The results based on density functional theory reveal that the monolayer is stable. It exhibits a tunable direct band gap and strong covalent bonding. Its ultralow lattice thermal conductivity (<0.38 W/mK at 300 K), attributed to the broken phonon selection rule for phonon-phonon scattering and a high level of anharmonicity, as reflected in the large Grüneisen parameter. Furthermore, the inclusion of four-phonon scattering introduces additional anharmonic phonon-phonon interactions, leading to a 50 % reduction in lattice thermal conductivity results in a significant enhancement of the thermoelectric figure of merit of 3.62 and power conversion efficiency of 30.89 % for the n-type Janus SiOS monolayer. highlighting its potential for efficient waste heat recovery applications.