Aqueous solution synthesis of (Sb, Bi)₂(Te, Se)₃ nanocrystals with controllable composition and morphology

The introduction of nanostructures has been considered as one of the promising strategies to enhance the thermoelectric performance of bulk materials. In this work, we report a low-cost and facile aqueous solution method to prepare (Sb, Bi)₂(Te, Se)₃ nanocrystals with controllable composition and morphology by using short ligands containing thiol, acid and amine groups. The control of the morphology of the nanostructures such as nanowires and nanosheets is studied, and both n-type and p-type nanoparticles have been prepared successfully. The results show that the thermal conductivities of these nanocrystals are effectively reduced due to phonon scattering and the thermoelectric performance is affected greatly by the morphology. TE measurements show that the electrical conductivity can be enhanced significantly by using Bi₂Te₃ nanosheets, and as a result, a maximum thermoelectric figure-of-merit (ZT) of 0.86 is obtained for Bi₂Te₃ nanosheets at 225 °C.