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 μV 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 microstructures 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

Enhanced thermoelectric performance of In-doped and AgCuTe-alloyed SnTe through band engineering and endotaxial nanostructures

Endotaxial nanostructures can reduce lattice thermal conductivity through enhancing phonon scattering without affecting electrical transport, leading to a high thermoelectric performance. On the other hand, band engineering can enhance electrical transport by improving the Seebeck coefficient through valence band convergence and the resonance level. In this paper, the synergistic effect of band engineering and endotaxial nanostructures was implemented in SnTe thermoelectric materials by alloying with AgCuTe and doping with Indium. The positron annihilation lifetime spectra show that the vacancy concentration in SnTe was reduced after alloying with AgCuTe, which led to a decreasing hole concentration and improved carrier mobility. Additionally, the diffusion of Ag in the matrix during the preparation can facilitate valence band convergence. Therefore, the power factor of SnTe is greatly increased to 18 μW cm−1 K−2 at 800 K, which can be further increased to 21.4 μW cm−1 K−2 at 800 K after In doping due to resonance level formation. Meanwhile, Cu2Te endotaxial nanostructures also can be observed in the TEM image after SnTe alloying with AgCuTe. So, the lattice thermal conductivity significantly reduced to 0.93 W m−1 K −1 in In-doped and AgCuTe-alloyed SnTe. Finally, we obtain an enhanced ZT value of 1.14 in Sn1.02In0.01Te-1%AgCuTe at 800 K