Enhanced thermoelectric properties of SnTe through core-shell structures and band engineering

The energy filtering effect is an effective method to improve the thermoelectric performance, and the core-shell structure with more interfaces and various potential barriers can introduce a stronger energy filtering effect. In this article, Ag2S@SnS core-shell structure is introduced into SnTe thermoelectric materials by incorporating Ag2S. When the concentration of Ag2S reaches 5%, the carrier concentration decreases by 41% compared with the undoped sample at room temperature,and the Seebeck coefficient increases to 140 mu V K-1 at 800 K. Positron annihilation lifetime spectra show that the addition of Ag2S alloy reduces the vacancy concentration in SnTe, which leads to the weakening of ionized impurity scattering and the increase of mobility. This makes up for the reduced mobility due to the presence of the core-shell structure and the secondary phases. The core-shell structure, the secondary phase formed by the diffusion of small Ag2S particles and the binding of elements in SnTe and point defects, all of these unique hierarchical micro-structures greatly reduce the lattice thermal conductivity of the samples over a wide temperature range. On this basis, In is doped into the material to introduce resonance levels and point defects, resulting in the lowest lattice thermal conductivity of 0.68 W m-1K -1 at 800 K. Moreover, The ZTave value obtained after In doping is 100% higher than that of single-alloyed Ag2S. The ZTmax value of Sn1.02In0.01Te-5%Ag2S increases to 1.02 at 800 K. This work provides a new idea for regulating thermoelectric performance.(c) 2023 Elsevier B.V. All rights reserved.