Effects of Interface Control Using Reduced Graphene Oxide (RGO) on the Thermoelectric Transport Properties of Polycrystalline SnSe Compounds

We report the effects of interface control using reduced graphene oxide (RGO) on the thermoelectric transport properties of polycrystalline SnSe compounds. Polycrystalline SnSe-RGO composites were prepared by the consolidation of SnSe powder coated with the RGO by hot pressing, and the RGO content was controlled to be 0, 0.2, 0.5 and 1 wt%. The incorporation of RGO did not induce any structural changes in the crystal structure of SnSe, and no additional secondary phase could be observed. The electrical conductivity of the composites increased with increasing RGO content. This increase was largely the result of increased hole concentration due to the hole Fermi liquid phenomenon at the SnSe-RGO interface, and it was elucidated by the reduced Seebeck coefficient with increasing RGO content. However, this tendency could only be clearly observed at relatively low temperatures, and the incorporation of the RGO did not lead to a significant increase in the power factor. The thermal conductivity of the composites decreased with the increase in RGO content, and revealed that there was additional phonon scattering at the grain boundary interfaces due to the existence of the RGO. These results, demonstrated that independent control of charge and thermal transport, i.e., phonon glass-electron crystal, could be realized by interface control using RGO in polycrystalline SnSe compounds.