Thermoelectric properties of semiconductor-metal composites produced by particle blending

Abstract

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.Peer ReviewedPostprint (published version

Doping and Surface Effects of CuFeS2 Nanocrystals Used in Thermoelectric Nanocomposites

“…In a last approach, we attempted to further increase electrical conductivity through a modulation doping strategy . CuFeS 2 NCs were blended with a small quantity of metal nanoparticles into a composite, where electrons can be injected from the metal into the CuFeS 2 host.…”

“…CuFeS 2 NCs were blended with a small quantity of metal nanoparticles into a composite, where electrons can be injected from the metal into the CuFeS 2 host. It has previously been shown with PbS‐metal nanoparticle composites that this strategy simultaneously provides free charge carriers for host doping and enhanced phonon scattering for decreasing thermal conductivity ,…”

“…Here, we only discuss the case of tin nanoparticles, introduced at a mass ratio of 3%, which gave the most promising results in terms of thermoelectric properties; the other examples are included in Supporting Information. 12 nm tin nanoparticles were prepared as previously described and the stabilizing ligands were not removed to enable homogeneous mixing with the CuFeS 2 NCs in organic solvent. EDX analysis of the obtained pellet shows a homogeneous distribution of Sn at the micro‐ and macroscales at a concentration of CuFeS 1.98 Sn 0.04 , in good agreement with the initial 3 wt % Sn concentration (3.0 wt %=4.0 at %).…”

High Thermoelectric Performance in Crystallographically Textured n-Type Bi2Te3–xSex Produced from Asymmetric Colloidal Nanocrystals

“…Additionally, the elemental Te present at grain boundaries ( Figure 4b) could contribute to further increase n through spillover of electrons from these Te domains to the Bi2Te3-xSex matrix, owing to the lower work function of the former (Figure 10). 5,17 As expected, charge carrier mobilities in the commercial samples were sensibly higher than in the nanomaterial: H = 286 cm 2 V -1 s -1 for the commercial sample in the cleavage plane; H = 136 cm 2 V -1 s -1 for the nanomaterial in the direction normal to the pressure axis; H = 71 cm 2 V -1 s -1 for the commercial sample in a plane normal to the cleavage plane; H = 61 cm 2 V -1 s -1 for the nanomaterial in the pressing direction.…”

“…11,12 While numerous approaches to produce nanomaterials exist, nanocrystal (NC)-based bottomup strategies allow an unparalleled combination of delicate control over material parameters with high production throughputs. 5,[13][14][15][16][17] In this regard, NC-based approaches offer clear advantages over currently more conventional nanomaterial fabrication methods, which lack sufficient control over material parameters, e.g. ball milling, 18 and/or are too costly for an eventual large volume industrial manufacturing of cost-effective TE modules, e.g.…”