Band and vacancy engineering in SnTe to improve its thermoelectric performance

Abstract

SnTe is a promising thermoelectric material with low cost and high stability. However, its performance is limited by the large energy separation between the light hole L band and the lower, heavy hole Σ band. Despite the efforts being made to induce band convergence, the improvements are very limited. In this work, the band flattening was first induced by Sb₂Te₃ alloying, which increases the density of states effective mass of the L band by 278%. The carrier mobility and lattice thermal conductivity were subsequently optimized through vacancy defect manipulation via Pb compensation. Eventually, a peak zT of 1.1 at 778 K and an average zT of 0.56 from 300 K to 778 K is achieved in (Sn_0.98Ge_0.05Te)_0.91(Sb₂Pb_0.5Te₃)_0.09, which is one of the best SnTe-based thermoelectric systems.