Thermoelectric properties of semiconductor-metal composites produced by particle blending

In the quest for more efficient thermoelectric material able to convert thermal to electrical energy and vice versa, composites that combine a semiconductor host having a large Seebeck coefficient with metal nanodomains that provide phonon scattering and free charge carriers are particularly appealing. Here, we present our experimental results on the thermal and electrical transport properties of PbS-metal composites produced by a versatile particle blending procedure, and where the metal work function allows injecting electrons to the intrinsic PbS host. We compare the thermoelectric performance of composites with microcrystalline or nanocrystalline structures. The electrical conductivity of the microcrystalline host can be increased several orders of magnitude with the metal inclusion, while relatively high Seebeck coefficient can be simultaneously conserved. On the other hand, in nanostructured materials, the host crystallites are not able to sustain a band bending at its interface with the metal, becoming flooded with electrons. This translates into even higher electrical conductivities than the microcrystalline material, but at the expense of lower Seebeck coefficient values.This work was supported by the European Regional Development Funds, the Framework 7 program under project UNION (No. FP7-NMP-2012-310250), and the Spanish MINECO Project BOOSTER (No. ENE2013-46624-C4-3-R). Y.L. thanks the China Scholarship Council (No. CSC 201406500003) for the scholarship support. M.I., O.D., and S.O. thank AGAUR for their Beatriu de Pinós postdoctoral Grant No. (2013 BP-A00344) and Ph.D. grants. M.V.K. acknowledges the partial financial support from the European Union (EU) via FP7 ERC Starting Grant 2012 (Project NANOSOLID, GA No. 306733). Authors also acknowledge the funding from Generalitat de Catalunya 2014 SGR 1638.Peer Reviewe