Ultrahigh zT from strong electron–phonon interactions and a low-dimensional Fermi surface

• Published in: Energy & environmental science Vol. 17; no. 5; pp. 1904 - 1915
• Main Authors: Ranganayakulu, V. K., Wang, Te-Hsien, Chen, Cheng-Lung, Huang, Angus, Ma, Ma-Hsuan, Wu, Chun-Min, Tsai, Wei-Han, Hung, Tsu-Lien, Ou, Min-Nan, Jeng, Horng-Tay, Lee, Chih-Hao, Chen, Kuei-Hsien, Li, Wen-Hsien, Brod, Madison K., Snyder, G. Jeffrey, Chen, Yang-Yuan
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 05.03.2024
• Subjects: Antimony; Bismuth; Electron phonon interactions; Fermi surfaces; Figure of merit; First principles; Inelastic scattering; Nesting; Neutron scattering; Phonons; Single crystals; Thermal conductivity; Thermoelectricity; Topology; Ultrahigh temperature
• ISSN: 1754-5692; 1754-5706
• DOI: 10.1039/D3EE04187E

The outstanding thermoelectric performance of GeTe has attracted significant attention in the research community in recent years. However, many of the underlying physical mechanisms that contribute to GeTe's exceptionally high figure of merit ( zT ) remain not fully understood. In this study, an Sb–Bi codoped GeTe single crystal (Ge 0.86 Sb 0.08 Bi 0.06 )Te with an ultrahigh zT of 2.7 at 700 K and a record high device zT of 1.41 in the temperature range of 300–773 K was synthesized and investigated. The ultrahigh zT is attributed to the extremely low lattice thermal conductivity induced by strong electron–phonon (EP) interactions as revealed by the experimentally observed Kohn anomaly, through inelastic neutron scattering (INS) measurements. First-principles calculations further demonstrate that the remarkable EP interaction arises from the Fermi surface nesting featured in a one-dimensional (double-walled) topology. Our finding unravels the ultrahigh- zT mechanism in GeTe-based materials, serving as an inspiring guide toward high thermoelectric performance.