Realization of high thermoelectric performance in solution-synthesized porous Zn and Ga codoped SnSe nanosheets

Abstract

SnSe is considered one of the most intriguing new thermoelectric materials. Polycrystalline SnSe offers a wide range of thermoelectric applications due to its facile synthetic processing and machinability. Herein, we have achieved a high average ZT of 0.8 as well as a high peak ZT of 1.86 in solution-synthesized porous Zn and Ga codoped SnSe nanosheets, generating a maximum energy conversion efficiency of 13.3%. High-density micro/nanopores are induced in the SnSe matrix, which are more effective for scattering phonons and reducing the thermal conductivity. The high density of micro/nanopores, nanosheet structure and dislocations contribute to an ultralow lattice thermal conductivity (0.157 W m⁻¹ K⁻¹ at 873 K). Meanwhile, Ga incorporation can induce band convergence and create resonance levels, producing a large Seebeck coefficient. Ga and Zn codoping contributes to a sharp increase in carrier concentration and an obviously increased electrical conductivity. The enhanced Seebeck coefficient and increased carrier concentration help in achieving a significant enhancement of the power factor over a wide temperature range in the porous Zn and Ga codoped SnSe nanosheets. Consequently, high thermoelectric performance is realized over a wide temperature range via the decoupling of electron–phonon transport in SnSe. This work opens up a great opportunity for designing prospective materials for thermoelectric applications with the aid of the solution synthesis route.