Significant improvement in thermoelectric performance of SnSe/SnS via nano-heterostructures

Abstract

In this work, we study theoretically the electronic and phonon transport properties of heterojunction SnSe/SnS, bilayer SnSe and SnS. The energy filtering effect caused by the nano heterostructure in SnSe/SnS induces an increase in the Seebeck coefficient, causing a large power factor. We calculate the phonon relaxation time and lattice thermal conductivity κ_L for the three structures; the heterogeneous nanostructure could effectively reduce κ_L due to the enhanced phonon boundary scattering at interfaces. The average κ_L notably reduces from around 3.3 (3.2) W m⁻¹ K⁻¹ for bilayer SnSe (SnS) to nearly 2.2 W m⁻¹ K⁻¹ for SnSe/SnS at 300 K. As a result, the average ZT (ZT_ave in b and c directions) reaches 1.63 with temperature range around 300–800 K, which is improved by 63% (25%) compared with that of bilayer SnSe (SnS). Our theoretical results show that the heterogeneous nanostructure is an innovative approach for improving the Seebeck coefficient and significantly reducing κ_L, effectively enhancing thermoelectric properties.