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

• Published in: Science (American Association for the Advancement of Science) Vol. 377; no. 6602; pp. 208 - 213
• Main Authors: Jiang, Binbin, Wang, Wu, Liu, Shixuan, Wang, Yan, Wang, Chaofan, Chen, Yani, Xie, Lin, Huang, Mingyuan, He, Jiaqing
• Format: Journal Article
• Language: English
• Published: Washington The American Association for the Advancement of Science 08.07.2022
• Subjects: Cations; Electrical properties; Entropy; Germanium; Scientific Concepts; Tellurium; Thermal conductivity; Thermoelectric materials
• ISSN: 0036-8075; 1095-9203; 1095-9203
• DOI: 10.1126/science.abq5815

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. Thermoelectric materials, many having relative simple compositions, convert heat into electricity. However, Jiang et al . found that adding more cations into a germanium tellurium–based material stabilized a phase with excellent thermoelectric properties. This high-entropy material has low thermal conductivity due to the cation disordering but improved symmetry that helps maintain good electrical properties. The material was used in several devices that showed a high thermoelectric efficiency. —BG A high-entropy material is an outstanding thermoelectric with a combination of delocalized electrons and localized phonons.