Thermoelectric Performance of Janus Monolayer ZnGeSTe from First-Principles Based Self-Consistent Transport Theory

Abstract

Thermal and electrical transport properties of Janus monolayer ZnGeSTe are investigated using first-principles-based self-consistent transport theory. The temperature-driven phonon dispersion and lattice thermal conductivity (κ_l) are evaluated up to the quartic anharmonicity, and consequently, the κ_l is reduced by 42.36% upon quartic anharmonicity at room temperature. The Seebeck coefficient (S), electrical conductivity (σ), and carrier thermal conductivity (κ_e) are calculated by considering individual carrier lifetimes, and consequently, due to the convergence and dispersion of multiple conduction bands, the large Seebeck coefficient (S) and the high electron mobility contribute to a higher power factor (PF = S²σ) for n-type doping. The optimal figure of merit (zT = PF/(κ_e + κ_l)) monotonically increases with the temperature, and the peak and average zT values are up to 1.16 and 0.79 in the operating temperature range of 500–800 K for n-type doping.