Highly enhanced thermoelectric properties of Bi2S3 via (Se, Cl)-co doping in hydrothermal synthesis process

Bi ₂S ₃ -based materials with low thermal conductivity and high Seebeck coefficient has been regarded as promising thermoelectric materials for years. To optimize the thermoelectric properties of Bi ₂S ₃ materials, (Se, Cl)-co-doped nanostructured Bi ₂S ₃ bulks were prepared by hydrothermal method combined with spark plasma sintering. The doping contents of Se and Cl in Bi ₂S ₃ depend on the reaction time of the hydrothermal process. A high power factor of 450 μWm ⁻¹ K ⁻² was achieved for Bi ₂S ₃ sample with the reaction time of 24 h owing to the substitution of S by Se and Cl. Meanwhile, a low thermal conductivity of 0.35 Wm ⁻¹ K ⁻¹ is obtained for the Bi ₂S ₃ sample with the reaction time of 18 h, owing to the strong phonon scattering caused by the high density of grain boundaries, pores and point defect. Therefore, benefiting from the improved electrical transport properties and reduced thermal conductivity, a peak ZT value of ~ 0.57 was obtained at 673 K for the Bi ₂S ₃ sample with the reaction time of 24 h.