Outstanding thermoelectric properties in solvothermal-synthesized Sn1-3xInxAg2xTe micro-crystals through defect engineering and band tuning
Due to the eco-friendly nature, tin telluride (SnTe) based thermoelectric materials have attracted extensive attention. Pristine SnTe suffers from low thermoelectric performance because of its large energy separation between two valence bands (heavy hole and light hole) and high thermal conductivity. In this study, we use In and Ag co-dopants to ameliorate the electrical and thermal transport properties of SnTe-based materials using a facile solvothermal method. From the theoretical calculation and performance evaluation, high-level In and Ag co-dopants can significantly converge two valence bands and increase the density of states near the Fermi level, leading to the enhanced Seebeck coefficient from ~95 μVK-1 in the pristine SnTe to ~178 μVK-1 in the Sn0.85In0.05Ag0.10Te. Comprehensive structural characterization shows that high-density strain field and dislocations are exist in the sintered pellets, together with the point defects, and grain boundaries yield remarkably low lattice thermal conductivity in the entire temperature range. As a result, a high peak figure of merit of ~1.38 at 823 K has been achieved in Sn0.85In0.05Ag0.10Te, outperforming most of SnTe-based materials. This study indicates that co-doping with high solubility can simultaneously tune band structure and engineer defects for achieving enhanced thermoelectric performance of SnTe-based materials.