Ultralow Thermal Conductivity in Diamondoid Structures and High Thermoelectric Performance in (Cu1–xAgx)(In1–yGay)Te2
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2021-04-13 |
| Journal | Journal of the American Chemical Society |
| Authors | Hongyao Xie, Shiqiang Hao, Trevor P. Bailey, Songting Cai, Yinying Zhang |
| Institutions | University of Michigan, Northwestern University |
| Citations | 85 |
Abstract
Section titled “Abstract”Owing to the diversity of composition and excellent transport properties, the ternary I-III-VI<sub>2</sub> type diamond-like chalcopyrite compounds are attractive functional semiconductors, including as thermoelectric materials. In this family, CuInTe<sub>2</sub> and CuGaTe<sub>2</sub> are well investigated and achieve maximum <i>ZT</i> values of ∼1.4 at 950 K and an average <i>ZT</i> of 0.43. However, both compounds have poor electrical conductivity at low temperature, resulting in low <i>ZT</i> below 450 K. In this work, we have greatly improved the thermoelectric performance in the quinary diamondoid compound (Cu<sub>0.8</sub>Ag<sub>0.2</sub>)(In<sub>0.2</sub>Ga<sub>0.8</sub>)Te<sub>2</sub> 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 Cu<sub>0.8</sub>Ag<sub>0.2</sub>In<sub>1-<i>x</i></sub>Ga<sub><i>x</i></sub>Te<sub>2</sub>. 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<sup>-1</sup> K<sup>-1</sup> at 850 K in Cu<sub>0.8</sub>Ag<sub>0.2</sub>In<sub>0.2</sub>Ga<sub>0.8</sub>Te<sub>2</sub>. 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 Cu<sub>0.8</sub>Ag<sub>0.2</sub>In<sub>0.2</sub>Ga<sub>0.8</sub>Te<sub>2</sub>. As a result, a maximum <i>ZT</i> of ∼1.5 at 850 K and an average <i>ZT</i> of 0.78 in the temperature range of 400-850 K are obtained, which is among the highest in the diamond-like compound family.