High thermoelectric performance of Ag doped SnTe polycrystalline bulks via the synergistic manipulation of electrical and thermal transport.

Ernzerhof (HSE) hybrid functional approximations based on the density functional theory (DFT) method were applied to investigate the electronic band structures of SnTe. First principles calculations indicate that Ag substitution in SnTe could effectively modify the valence band structures and decrease the energy separation between valence bands, Delta EVBL-sigma, which will enhance the Seebeck coefficient. All the fabricated Ag doped SnTe samples show the same crystal structure as cubic SnTe. Compared to the pure SnTe sample, the Ag doped ones exhibit greatly enhanced thermoelectric performance, especially at high temperatures, with the highest figure-of-merit of around 1.35 achieved at 900 K, by concurrent optimization of the electrical and thermal transport properties.