Electronic origin of the high thermoelectric performance of GeTe among the p-type group IV monotellurides

• Published in: NPG Asia materials Vol. 9; no. 3; p. e353
• Main Authors: Li, Juan, Chen, Zhiwei, Zhang, Xinyue, Sun, Yongxing, Yang, Jiong, Pei, Yanzhong
• Format: Journal Article
• Language: English
• Published: Tokyo Nature Publishing Group 01.03.2017
• Subjects: Carriers; Electronics; Intermetallics; Lead base alloys; Lead tellurides; Optimization; Thermoelectricity; Transport properties
• ISSN: 1884-4049; 1884-4057; 1884-4057
• DOI: 10.1038/am.2017.8

PbTe and SnTe in their p-type forms have long been considered high-performance thermoelectrics, and both of them largely rely on two valence bands (the first band at L point and the second one along the Σ line) participating in the transport properties. This work focuses on the thermoelectric transport properties inherent to p-type GeTe, a member of the group IV monotellurides that is relatively less studied. Approximately 50 GeTe samples have been synthesized with different carrier concentrations spanning from 1 to 20 × 1020 cm-3 , enabling an insightful understanding of the electronic transport and a full carrier concentration optimization for the thermoelectric performance. When all of these three monotellurides (PbTe, SnTe and GeTe) are fully optimized in their p-type forms, GeTe shows the highest thermoelectric figure of merit (zT up to 1.8). This is due to its superior electronic performance, originating from the highly degenerated Σ band at the band edge in the low-temperature rhombohedral phase and the smallest effective masses for both the L and Σ bands in the high-temperature cubic phase. The high thermoelectric performance of GeTe that is induced by its unique electronic structure not only provides a reference substance for understanding existing research on GeTe but also opens new possibilities for the further improvement of the thermoelectric performance of this material.