Cobalt doping of Mg3Sb2 monolayer: Improved thermoelectric performance

Abstract

Mg3Sb2 is a layered thermoelectric (TE) material with excellent TE performance. In this work, focus on Mg3Sb2 monolayer, we employed virtual crystal approximation (VCA) to simulate the structure of Co doping Mg3Sb2 monolayer, the doping atoms ratio is 0.1%, namely Mg2.999Co0.001Sb2. The first-principles calculation within the framework of density functional theory (DFT) combined with non-equilibrium Green's Function (NEFG) method and Landauer-Buttiker theory have been used to calculate the phonon spectrum, the electronic structures, the TE parameters, the electron and phonon transmission spectra. From the results we find that doping enhanced the TE transformation efficiency. The maximum ZT of Mg3Sb2 monolayer is 1.38 at 200 K, which appears at the chemical potential of 0.04 eV. Relative to the Mg3Sb2 monolayer, the maximum ZT of Mg2.999Co0.001Sb2 is improved, which can reach 3.22 at 200 K for n-type doping. Our research demonstrates that a little amount of Co doping can improve the TE performance. It provides a new idea for the related experiments.