Two-Dimensional Janus VSeTe monolayer with ultra-low lattice thermal conductivity for Thermoelectric Application*

Janus 2D materials have shown tremendous potential for thermoelectric applications [1]. In this work, we have calculated the electronic and thermoelectric properties of VSeTe monolayer with the help of Density functional theory and Boltzmann transport equation [2,3].  The electronic band structure revealed the semiconducting nature of VSeTe, with an indirect band gap of 0.28eV. The phonon dispersion curve established the dynamic stability of the proposed structure. Morever, to confirm the thermal stability of the system,  Ab initio molecular dynamics (AIMD) simulations were performed at 300K. We have also calculated the elastic constant to check the mechanical stability of the structure. The thermoelectric parameters such as Seebeck coefficient, power factor, and electrical conductivity have been calculated under constant relaxation time approximation at temperatures of 300K, 600K, and 800K. The lattice thermal conductivity (K_l ) at room temperature has been found to be very low in VSeTe monolayer as compared to other Janus monolayers [1]. An ultralow value of K_l of 0.19 W/mK at room temperature was observed in the Janus monolayer VSeTe, primarily due to  very low group velocity and short phonon lifetime in VSeTe. This ultralow lattice thermal conductivity and high power factor, result in a high thermoelectric figure of merit close to the value of 1 at room temperature. Our finding indicates the potential application of VSeTe monolayer for thermoelectric devices in energy harvesting at room temperature.