Maximization of transporting bands for high-performance SnTe alloy thermoelectrics

Abstract

Environment-friendly thermoelectric SnTe has recently attracted much attention as a top candidate for replacing conventional p-type PbTe. Effective strategies leading to great advancements in this material are typified by manipulation of valence bands and chemical defects, among of which MgTe- and Cu2Te-alloying are particularly successful, respectively, for valence band convergence and lattice thermal conductivity minimization. However, pristine SnTe enables a MgTe solubility of only ∼12%, which might limit the full convergence of possibly transporting bands for an electronic performance maximization. In this work, we show an approach to increase the MgTe solubility up to ∼20%, leading to an involvement of one more highly degenerated valence band Λ for charge transport in addition to existing L and Σ bands. Such a collection of many transporting valence bands enables a great improvement in electronic performance, as well as a significant enhancement in thermoelectric figure of merit with a well-reduced lattice thermal conductivity by the point defects introduced in these SnTe alloys.