Abstract
Here, we achieve a high peak ZT of 2.5 as well as an exceptional average ZT of 1.9 through nanotwin architecture and inducing ultra-high valley degeneracy. We find that nanotwins, ordered vacancy arrays and point defects serve as intense phonon scattering centers for enhancing wide-frequency phonon scattering, resulting in ultralow lattice thermal conductivity in GeTe. Interestingly, density-functional theory calculations reveal that CuBiS2 alloying realizes refined valence band alignment in GeTe, generating an ultra-high valley degeneracy of 22. The dramatic enhancement of the Seebeck coefficient induced by the ultra-high valley degeneracy contributes to remarkably enhanced power factor over a very wide temperature range. The maximum power factor reaches as high as 49 μW cm-1 K-2. Consequently, a high peak ZT as well as a large average ZT are realized in GeTe without involving toxic elements. Importantly, the presence of nanotwins boundaries in GeTe effectively provides adequate barriers to block dislocation motion, leading to excellent hardness and compressive strength. Our finding provides a feasible pathway to design fascinating thermoelectric materials with high thermoelectric performance and mechanical properties.
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The authors declare that all data supporting the findings of this study are available within the article and its Supplementary Information files or from the corresponding author.
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Acknowledgements
The work was supported by the National Natural Science Foundation of China (No. 52071182 to G.D.T., 52472250 to H.J.W., and 12474016 to Y.S.Z.), “Qinglan Project” of the Young and Middle-aged Academic Leader of Jiangsu Province (to G.D.T.), the Fundamental Research Funds for the Central Universities (No. 202510 to G.D.T.), and the program of “Distinguished Expert of Taishan Scholar” (No. tstp20221124 to Y.S.Z.).
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G.D.T. conceived the idea, designed the experiments, and supervised the research. S.L. prepared samples, analyzed data, and wrote the paper. Y.X.Y., Y.Z., and H.J.W. accomplished the microstructural characterizations and analyzed data. X.Y.F., X.B.L., and Y.S.Z. carried out the DFT calculations. Y.G. performed the fabrication and measurements for the single-leg module. J.J.N., P.B.P., and G.Z.L. helped measure the properties. All authors analyzed the results and coedited the manuscript.
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Li, S., Yang, Y., Fei, X. et al. Nanotwin architecture and ultra-high valley degeneracy lead to high thermoelectric performance in GeTe-based thermoelectric materials. Nat Commun (2026). https://doi.org/10.1038/s41467-026-68908-0
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DOI: https://doi.org/10.1038/s41467-026-68908-0
