First Principles Investigation on Thermoelectric Properties of Monolayer 1t-Ag6s2

Abstract

We obtained a new material called monolayer 1T-Ag6S2 by replacing metal atoms in 1T phase transition-metal dichalcogenide sulfides (TMDs) with octahedral Ag6 cluster. Subsequently, the thermoelectric transport properties of monolayer 1T-Ag6S2 were systematically investigated using first-principles calculation. The results demonstrate that the introduction of Ag6 clusters effectively optimizes the electronic structure of the material and balances the relationship between the Seebeck coefficient and electrical conductivity, consequently leading to an enhanced power factor (14.9 and 5.6 mW/mK2 along the x and y axis at 500 K, respectively). The complex crystal structure leads to convoluted phonon paths and reduced phonon vibration frequencies, resulting in extremely low lattice thermal conductivity κl (0.20 and 0.17 W/mK at 500 K along the x and y axis, respectively). The monolayer 1T-Ag6S2 demonstrates a significantly high thermoelectric figure of merit ZT of 3.14 (3.15) along the x (y) axis at 500 K, significantly higher than conventional TMDs materials. Such excellent thermoelectric properties suggest that monolayer 1T-Ag6S2 is a promising thermoelectric (TE) material. Our works provide a theoretical basis for cluster substitution in optimizing the thermoelectric properties of materials, and provide a useful reference for subsequent research.

Keywords: 1T-Ag6S2, Ag6 clusters, Thermoelectricity, Transport Property, First-principles calculations