Superior thermoelectric performance of α-Se2Te monolayer

Abstract

Based on the first-principles of density functional theory and Boltzmann transport theory, we report two-dimensional (2D) α-Se2Te monolayer to be a high-performance medium temperature p-type thermoelectric material with low lattice thermal conductivity (κl), high power factor (PF) and high dimensionless figure of merit (ZT). At the temperature of 700 K, PF is up to 3.77 and 11.5 mW m−1 K−2, ZT is up to 0.55 and 1.91 in appropriate doping level for n- and p-types, respectively, and kl is as low as 2.09 W m−1 K−1. We also examine the effect of spin-orbital coupling (SOC) on the carrier transport and find that with SOC, PF and hence ZT will be reduced significantly due to the reduced band gap. The higher PF of p-type than that of n-type is evidently due to the flatter valence band edge than conduction band edge. Low kl is inevitably attributed to the strong lattice anharmonicity.