Solvothermally silver doping boosting the thermoelectric performance of polycrystalline Bi2Te3

Bismuth telluride (Bi2Te3) is one of the most promising thermoelectric materials for commercial application at room temperature, but the thermoelectric performance of these materials still needs to be improved. In this study, we report a type of solvothermally Ag-doped Bi2Te3 microplate. By sintering these microplates into polycrystalline bulk materials, a high room-temperature figure of merit of 1 has been achieved. Based on comprehensive micro/nanostructural characterizations, we found that the solvothermally doped Ag in Bi2Te3 plays two main roles, namely as the dopants that effectively induce the point defects of AgBi and forming Ag2Te nanophases. AgBi can provide additional hole charge carriers, effectively adjusting the initially high electron carrier concentration in the system, while the Ag2Te nanophases effectively trigger energy filtering effect to maintain a high Seebeck coefficient, thereby contributing to a competitively high power factor of 25.5 μW cm−1 K−2 at 298 K. Simultaneously, a low thermal conductivity of 0.74 W m−1 K−1 is obtained due to the strong phonon scattering at various lattice imperfections, induced by the solvothermally Ag-doping, which include point defects, grain/phase boundaries, local lattice distortions, and dislocations. This work fills the gap in knowledge on the solvothermally Ag-doping mechanism in Bi2Te3 and provides guidance for the innovative design of high-performing inorganic thermoelectrics.