Xie Hongyao, Liu Yukun, Zhang Yinying, Hao Shiqiang, Li Zhi, Cheng Matthew, Cai Songting, Snyder G Jeffrey, Wolverton Christopher, Uher Ctirad, Dravid Vinayak P, Kanatzidis Mercouri G
Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States.
Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States.
J Am Chem Soc. 2022 May 25;144(20):9113-9125. doi: 10.1021/jacs.2c02726. Epub 2022 May 10.
The understanding of thermoelectric properties of ternary I-III-VI type (I = Cu, Ag; III = Ga, In; and VI = Te) chalcopyrites is less well developed. Although their thermal transport properties are relatively well studied, the relationship between the electronic band structure and charge transport properties of chalcopyrites has been rarely discussed. In this study, we reveal the unusual electronic band structure and the dynamic doping effect that could underpin the promising thermoelectric properties of CuAgGaTe compounds. Density functional theory (DFT) calculations and electronic transport measurements suggest that the CuAgGaTe compounds possess an unusual non-parabolic band structure, which is important for obtaining a high Seebeck coefficient. Moreover, a mid-gap impurity level was also observed in CuAgGaTe, which leads to a strong temperature-dependent carrier concentration and is able to regulate the carrier density at the optimized value for a wide temperature region and thus is beneficial to obtaining the high power factor and high average of CuAgGaTe compounds. We also demonstrate a great improvement in the thermoelectric performance of CuAgGaTe by introducing Cu vacancies and ZnTe alloying. The Cu vacancies are effective in increasing the hole density and the electrical conductivity, while ZnTe alloying reduces the thermal conductivity. As a result, a maximum of 1.43 at 850 K and a record-high average of 0.81 for the CuAgGaTe-0.5%ZnTe compound are achieved.
对三元 I-III-VI 型（I = Cu、Ag；III = Ga、In；VI = Te）黄铜矿热电性质的理解尚不完善。尽管它们的热输运性质已得到较为充分的研究，但黄铜矿的电子能带结构与电荷输运性质之间的关系却鲜有讨论。在本研究中，我们揭示了异常的电子能带结构和动态掺杂效应，这些可能是 CuAgGaTe 化合物具有良好热电性质的基础。密度泛函理论（DFT）计算和电子输运测量表明，CuAgGaTe 化合物具有异常的非抛物线能带结构，这对于获得高塞贝克系数很重要。此外，在 CuAgGaTe 中还观察到一个带隙中间杂质能级，这导致载流子浓度强烈依赖于温度，并且能够在很宽的温度范围内将载流子密度调节到最佳值，因此有利于获得 CuAgGaTe 化合物的高功率因子和高平均值。我们还通过引入 Cu 空位和 ZnTe 合金化证明了 CuAgGaTe 热电性能的大幅提升。Cu 空位有效地增加了空穴密度和电导率，而 ZnTe 合金化降低了热导率。结果，CuAgGaTe-0.5%ZnTe 化合物在 850 K 时达到了 1.43 的最大值以及 0.81 的创纪录高平均值。
