Thermoelectric power factor enhancement through thermal management with resonant level effect is experimentally demonstrated in SiGeAu composite system.

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 S 2σ 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 S 2σ 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.

Thin film thermoelectric materials have drawn much attention for realizing one-chip stand-alone power sources of Internet of Things devices. Here, we fabricate two types of the nanostructured Si films with high crystallinity: Si films containing β-FeSi 2 nanodots with a wider nanodot size distribution of ∼5-120 nm and Si films containing α-FeSi 2 nanodots with a narrow size distribution of ∼5-20 nm. The thermal conductivity of these films is lower than those of Si-silicide nanocomposite bulks. Interestingly, Si films containing β-FeSi 2 nanodots show about two times lower thermal conductivity than Si films containing α-FeSi 2 nanodots. This is because the widely-size-distributed β-FeSi 2 nanodots can effectively work as phonon scattering centers due to hierarchical architectures. These films also exhibited a high power factor due to the small amount of point defects and single crystalline epitaxial interfaces, regardless of the iron silicide phase of nanodots. These detailed investigations will open a road for realizing high-performance thin film thermoelectric materials.