Strengthened phonon scattering and band convergence synergistically realize the high-performance SnTe thermoelectric

Abstract

SnTe has been considered as a nontoxic alternative to the PbTe thermoelectric (TE), but its ZT value is severely limited by the high thermal conductivity and low Seebeck coefficient. Here, we demonstrate that the TE properties of p-type SnTe can be significantly improved by strengthening phonon scattering and band convergence based on the component design. Defect engineering by AgCuTe alloying introduces multiscale scattering centers for heat-carrying phonons and results in a rather low lattice thermal conductivity of 0.35 W m⁻¹ K⁻¹ at 833 K. The reduced energy separation of valence band maxima by Cd doping promotes the band convergence and enhances the Seebeck coefficient. Moreover, the diluted I doping optimizes the hole concentration and suppresses the electronic thermal conductivity. Consequently, a peak ZT of 1.75 at 833 K is achieved in the p-type (Sn_0.96Cd_0.04Te_0.99I_0.01)_0.94(AgCuTe)_0.06 sample. This work provides a feasible and efficient way to improve the TE performance of SnTe, and thus accelerates the application of this eco-friendly TE material.