Realizing the high thermoelectric performance of highly preferentially oriented SnSe based nanorods via band alignment

Abstract

Polycrystalline SnSe is considered as a highly promising candidate for thermoelectric applications due to its facile processing, machinability and scale-up applications. Here, we report an extraordinary peak ZT of 2.4 as well as a high average ZT of 0.9 for Ge and S codoped SnSe nanorods synthesized by a facile hydrothermal route. The highly preferentially oriented SnSe nanorods along [100] play a dominant role in scattering heat carrying phonons, resulting in ultralow lattice thermal conductivity (0.15 W m⁻¹ K⁻¹ at 873 K). The band alignment in the electronic structure of SnSe is promoted by Ge doping, contributing to a giant Seebeck coefficient and a largely enhanced power factor of 5.84 μW cm⁻¹ K⁻² at 873 K. An extraordinarily high peak ZT and a high average ZT are achieved within a wide temperature range for polycrystalline SnSe without involving toxic elements. Moreover, the reported material exhibits outstanding hardness and compressive strength induced by grain refinement. The high thermoelectric performance and mechanical properties of polycrystalline SnSe open realistic pathways for its widespread application in waste heat recovery and power generation.