Effect of a self-assembled 3D flower-like hierarchical architecture on the thermoelectric properties of Ag-doped Bi2S3

Powder samples of Bi2S3 and Ag-doped Bi2S3 compounds were successfully synthesized via the solvothermal method. The synthesized powders were consolidated using the cold-press method and annealed at 300 °C for 3 h. The cross-sections of the consolidated samples exhibited a densely packed hierarchical architecture micro-flower-like morphology. The effect of Ag doping on the thermoelectric properties of the samples was systematically studied. The results showed that Ag doping had considerable effects on the morphology, leading to grain boundary scattering and point defects. The addition of 0.025% Ag led to an 81% enhancement in electrical conductivity (σ) at 550 K. However, a reduction in the Seebeck coefficient (S) was observed, and the power factor (S2σ) was enhanced. Owing to the scattering of all-scale phonons caused by the hierarchical architecture, a low thermal conductivity of 0.407 W m−1 K−1 at 483 K was obtained, which is one of the low values among the reported Bi2S3 materials. The maximum zT was obtained as 0.06 at 543 K for the 0.025% Ag-doped Bi2S3 sample.