Xie Hongyao, Hao Shiqiang, Bailey Trevor P, Cai Songting, Zhang Yinying, Slade Tyler J, Snyder G Jeffrey, Dravid Vinayak P, Uher Ctirad, Wolverton Christopher, 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. 2021 Apr 21;143(15):5978-5989. doi: 10.1021/jacs.1c01801. Epub 2021 Apr 13.
Owing to the diversity of composition and excellent transport properties, the ternary I-III-VI type diamond-like chalcopyrite compounds are attractive functional semiconductors, including as thermoelectric materials. In this family, CuInTe and CuGaTe are well investigated and achieve maximum values of ∼1.4 at 950 K and an average of 0.43. However, both compounds have poor electrical conductivity at low temperature, resulting in low below 450 K. In this work, we have greatly improved the thermoelectric performance in the quinary diamondoid compound (CuAg)(InGa)Te by understanding and controlling the effects of different constituent elements on the thermoelectric transport properties. Our combined theoretical and experimental effort indicates that Ga in the In site of the lattice decreases the carrier effective mass and improves the electrical conductivity and power factor of CuAgInGaTe. Furthermore, Ag in the Cu site strongly suppresses the heat transport via the enhanced acoustic phonon-optical phonon coupling effects, leading to the ultralow thermal conductivity of ∼0.49 W m K at 850 K in CuAgInGaTe. Defect formation energy calculations suggest intrinsic Cu vacancies introduce defect levels that are important to the temperature-dependent hole density and electrical conductivity. Therefore, we introduced extra Cu vacancies to optimize the hole carrier density and improve the power factor of CuAgInGaTe. As a result, a maximum of ∼1.5 at 850 K and an average of 0.78 in the temperature range of 400-850 K are obtained, which is among the highest in the diamond-like compound family.
由于其组成的多样性和优异的输运特性，三元I-III-VI型类金刚石黄铜矿化合物是有吸引力的功能半导体，包括作为热电材料。在这个家族中，CuInTe和CuGaTe已得到充分研究，并在950 K时达到约1.4的最大值，平均为0.43。然而，这两种化合物在低温下的电导率都很差，导致在450 K以下的ZT值较低。在这项工作中，我们通过理解和控制不同组成元素对热电输运特性的影响，极大地提高了五元类金刚石化合物(CuAg)(InGa)Te的热电性能。我们理论和实验相结合的研究表明，晶格In位点中的Ga降低了载流子有效质量，提高了CuAgInGaTe的电导率和功率因子。此外，Cu位点中的Ag通过增强声学声子-光学声子耦合效应强烈抑制热输运，导致CuAgInGaTe在850 K时的超低热导率约为0.49 W m⁻¹ K⁻¹。缺陷形成能计算表明，本征Cu空位引入的缺陷能级对温度依赖的空穴密度和电导率很重要。因此，我们引入额外的Cu空位来优化空穴载流子密度，提高CuAgInGaTe的功率因子。结果，在850 K时获得了约1.5的最大ZT值，在400-850 K温度范围内的平均ZT值为0.78，这在类金刚石化合物家族中是最高的之一。
