Dong Jinfeng, Liu Yukun, Li Zhi, Xie Hongyao, Jiang Yilin, Wang Honghui, Tan Xian Yi, Suwardi Ady, Zhou Xiaoyuan, Li Jing-Feng, Wolverton Christopher, Dravid Vinayak P, Yan Qingyu, Kanatzidis Mercouri G
School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore.
Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States.
J Am Chem Soc. 2024 Jun 26;146(25):17355-17364. doi: 10.1021/jacs.4c04453. Epub 2024 Jun 13.
GeSe, an analogue of SnSe, shows promise in exhibiting exceptional thermoelectric performance in the phase. The constraints on its dopability, however, pose challenges in attaining optimal carrier concentrations and improving values. This study demonstrates a crystal structure evolution strategy for achieving highly doped samples and promising s in GeSe via LiBiTe alloying. A rhombohedral phase (3) can be stabilized in the GeSe-LiBiTe system, further evolving into a cubic (3) phase with a rising temperature. The band structures of GeSe-LiBiTe in the rhombohedral and cubic phases feature a similar multiple-valley energy-converged valence band of L and Σ bands. The observed high carrier concentration (∼10 cm) reflects the effective convergence of these bands, enabling a high density-of-states effective mass and an enhanced power factor. Moreover, a very low lattice thermal conductivity of 0.6-0.5 W m K from 300 to 723 K is achieved in 0.9GeSe-0.1LiBiTe, approaching the amorphous limit value. This remarkably low lattice thermal conductivity is related to phonon scattering from point defects, planar vacancies, and ferroelectric instability-induced low-energy Einstein oscillators. Finally, a maximum value of 1.1 to 1.3 at 723 K is obtained, with a high average value of over 0.8 (400-723 K) in 0.9GeSe-0.1LiBiTe samples. This study establishes a viable route for tailoring crystal structures to significantly improve the performance of GeSe-related compounds.
GeSe是SnSe的类似物，有望在该相中展现出卓越的热电性能。然而，其可掺杂性方面的限制给实现最佳载流子浓度和提高性能值带来了挑战。本研究展示了一种晶体结构演化策略，通过LiBiTe合金化来实现GeSe的高掺杂样品和有前景的性能。在GeSe-LiBiTe体系中可以稳定存在菱方相（3），随着温度升高进一步演化为立方相（3）。菱方相和立方相的GeSe-LiBiTe的能带结构具有相似的L和Σ带的多谷能量收敛价带。观察到的高载流子浓度（约10厘米）反映了这些能带的有效收敛，使得态密度有效质量较高且功率因子增强。此外，在0.9GeSe-0.1LiBiTe中，从300到723 K实现了非常低的晶格热导率，为0.6 - 0.5 W m K，接近非晶极限值。这种极低的晶格热导率与点缺陷、平面空位以及铁电不稳定性诱导的低能爱因斯坦振荡器引起的声子散射有关。最后，在0.9GeSe-0.1LiBiTe样品中，在723 K时获得了1.1至1.3的最大值，在400 - 723 K范围内平均性能值超过0.8。本研究为定制晶体结构以显著提高GeSe相关化合物的性能建立了一条可行的途径。
