High figure-of-merit and power generation in high-entropy GeTe-based thermoelectrics

TLDR

The high‑entropy concept expands compositional space, leading to unusual transport phenomena and excellent thermoelectric performance. The authors propose a paradigm for tuning electron and phonon localization via entropy manipulation and demonstrate a route to improve high‑entropy thermoelectric performance. Increasing entropy raises crystal symmetry, delocalizing electrons in the distorted rhombohedral structure to cause band convergence and better electrical properties, while entropy‑induced disorder localizes phonons, damping transverse phonon propagation, increasing anharmonicity, and reducing lattice thermal conductivity. The study achieved a figure‑of‑merit of 2.7 at 750 K and an experimental conversion efficiency of 13.3 % at a ΔT of 506 K using a fabricated segmented module.

Abstract

The high-entropy concept provides extended, optimized space of a composition, resulting in unusual transport phenomena and excellent thermoelectric performance. By tuning electron and phonon localization, we enhanced the figure-of-merit value to 2.7 at 750 kelvin in germanium telluride-based high-entropy materials and realized a high experimental conversion efficiency of 13.3% at a temperature difference of 506 kelvin with the fabricated segmented module. By increasing the entropy, the increased crystal symmetry delocalized the distribution of electrons in the distorted rhombohedral structure, resulting in band convergence and improved electrical properties. By contrast, the localized phonons from the entropy-induced disorder dampened the propagation of transverse phonons, which was the origin of the increased anharmonicity and largely depressed lattice thermal conductivity. We provide a paradigm for tuning electron and phonon localization by entropy manipulation, but we have also demonstrated a route for improving the performance of high-entropy thermoelectric materials.