High ZT 2D Thermoelectrics by Design: Strong Interlayer Vibration and Complete Band‐Extrema Alignment. (6th April 2020)

• Record Type: Journal Article
• Authors: Zhang, Xiwen; Liu, Chenhan; Tao, Yi; Li, Yunhai; Guo, Yilv; Chen, Yunfei; Zeng, Xiao Cheng; Wang, Jinlan
• Is Part Of: Advanced functional materials. Volume 30:Number 22(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-04-06
• Subjects: 2D thermoelectrics -- band‐extrema alignment -- figure of merit -- interlayer‐related vibration; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.202001200
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract: The discovery of a record high figure of merit (ZT) of ≈2.6 associated with bulk SnSe has stimulated considerable enthusiasm in searching for 2D systems with similar high ZT. However, previously reported 2D thermoelectric (TE) materials generally possess very low ZT due to the high lattice thermal conductivity (κL ) and/or small power factor (PF). Herein, a very high ZT (≈2.08) value associated with atomically thin 2D KAgSe nanosheet is reported, which also exhibits an unprecedented low intrinsic κL (≈0.03 Wm −1 K −1 at 700 K for trilayer) and fairly large PF. The low κL mainly stems from the high lattice anharmonicity induced by both the "interfacial shear slip" vibrations and the asymmetric "AgSe pair" vibrations from distorted AgSe4 tetrahedrons. Meanwhile, the complete band‐extrema alignment and coexistence of heavy and light bands result in an optimal Seebeck coefficient and electrical conductivity, thereby a large PF. This work suggests not only an alternative way to acquiring high lattice anharmonicity but also a highly competitive 2D TE candidate for wide applications. Abstract : The pursuit of high‐ZT in 2D thermoelectric materials has attracted enormous attention. Herein, a very promising 2D high‐ZT candidate, atomically thin KAgSe nanosheet, is reported and it demonstrates an unprecedented low intrinsic κL and fairly large power factor. Insights to achieve high‐ZT are discussed and materials with strong "interfacial shear slip" vibrations coupled with complete band‐extreme alignment have strong potential.