Weak interatomic interactions induced low lattice thermal conductivity in 2D/2D PbSe/SnSe vdW heterostructure

Inspired by the excellent thermoelectric performance of two-dimensional (2D) PbSe and SnSe monolayers, the thermal and electronic transport properties of 2D/2D PbSe/SnSe heterostructure is theoretically evaluated using first-principles calculations and Boltzmann transport theory. An indirect bandgap of 1.06 eV for the PbSe/SnSe heterostructure is calculated by the combination of Heyd-Scuseria-Ernzerhof (HSE06) functional and spin-orbit coupling (SOC) effect. The mechanical, thermal and dynamic stabilities of the PbSe/SnSe heterostructure are further demonstrated by the elastic modulus, ab initio molecular dynamics (AIMD) simulations and phonon dispersion curves, respectively. The honeycomb-like wrinkled structure introduce the asymmetry at the interface of the PbSe/SnSe heterostructure, thereby leading to enhanced phonon boundary scattering. Concurrently, the antibonding states originated from the weak interatomic interactions within PbSe/SnSe heterostructure also lead to strong anharmonicity. This synergistic effect of pronounced scattering and heightened anharmonicity contributes to the low lattice thermal conductivity of PbSe/SnSe heterostructure. The thermoelectric properties of PbSe/SnSe heterostructure are further investigated along the x- and y-direction, which reveals that the p-type PbSe/SnSe heterostructure attains an optimal dimensionless figure-of-merit (ZT) of 2.6 at 900 K along the y-direction. Our present study not only offers the fundamental insights into the thermal and electronic transport properties of the PbSe/SnSe heterostructure, but also provides an effective and feasible strategy for the design of 2D layered heterostructures as promising thermoelectric materials.