High thermoelectric performance of Pb and Er co-doped polycrystalline SnSe via endogenous hetero-/homo-nanostructures and band alignment

Abstract

SnSe demonstrates unparalleled potential in thermoelectric applications, combining non-toxicity, low cost, and abundant sources. Furthermore, polycrystals have good machinability and are easier to prepare. Here, we report a high peak ZT of 2.0 at 873 K in Pb and Er co-doped polycrystalline SnSe prepared through the hydrothermal method. An ultralow lattice thermal conductivity of 0.13 W m⁻¹ K⁻¹ at 873 K is obtained by introducing endogenous hetero-/homo-structural nanoprecipitates and Sn vacancies into the matrix to construct a multiscale scattering structure for phonons. Meanwhile, with the band alignment and flattening induced by Pb and Er co-doping, the effective mass is increased thus leading to a large Seebeck coefficient. Pb and Er co-doping not only optimizes the energy band structure of SnSe, but also optimizes the carrier concentration, thus simultaneously leading to enhanced electrical conductivity as well as enhanced electrical transport properties. Therefore, a high peak ZT of 2.0 is achieved in Pb and Er co-doped polycrystalline SnSe due to the markedly ultralow thermal conductivity and enhanced power factor. This work proposes a novel approach to synergistically regulate the electrical and thermal transport properties of polycrystalline SnSe-based thermoelectric materials through constructing endogenous hetero-/homo-nanostructures combined with band alignment.