Methodology of Thermoelectric Power Factor Enhancement by Nanoscale Thermal Management in Bulk SiGe Composites

We propose the methodology for thermoelectric power factor enhancement using nanoscale thermal management. The thermally managed composite is composed of a high electrical conductivity (σ) material with high thermal conductivity (κ), and a high Seebeck coefficient (S) material with  lowered κ by nanostructuring, where a large temperature difference is applied to high-S materials. This brings out two better properties (high S and high σ) from the two different materials. We experimentally demonstrate that S²σ is enhanced in SiGe-Au composites compared with SiGe materials, where SiGe is used as a high-S material with low κ in Si-based materials and Au is used as a high-σ material with high κ. Therein, the nanostructured Ge-rich domains including Au with Ge nanocrystals form and work as a high-S and ultra-low-κ material. This SiGe-Au composite achieves the highest S²σ value (22 μW cm^–1 K^–2) among reported SiGe-related bulk materials (Ge fraction: 10–80%) at room temperature. This methodology would be expected as a guideline for thermoelectric performance enhancement.