Hierarchical Architectural Structures Induce High Performance in n‐Type GeTe‐Based Thermoelectrics

• Published in: Advanced functional materials Vol. 33; no. 14
• Main Authors: Wang, De‐Zhuang, Liu, Wei‐Di, Li, Meng, Zheng, Kun, Hu, Hanwen, Yin, Liang‐Cao, Wang, Yifeng, Zhu, He, Shi, Xiao‐Lei, Yang, Xiaoning, Liu, Qingfeng, Chen, Zhi‐Gang
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01.04.2023
• Subjects: Alloying; Carrier density; devices; figure of merit; Free energy; Heat of formation; Materials science; Modules; n‐type GeTe; Point defects; Power factor; Precipitates; Thermal conductivity; Thermoelectricity; thermoelectrics
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202213040

Compatible p‐ and n‐type materials are necessary for high‐performance GeTe thermoelectric modules, where the n‐type counterparts are in urgent need. Here, it is reported that the p‐type GeTe can be tuned into n‐type by decreasing the formation energy of Te vacancies via AgBiTe2 alloying. AgBiTe2 alloying induces Ag2Te precipitates and tunes the carrier concentration close to the optimal level, leading to a high‐power factor of 6.2 µW cm−1 K−2 at 423 K. Particularly, the observed hierarchical architectural structures, including phase boundaries, nano‐precipitates, and point defects, contribute an ultralow lattice thermal conductivity of 0.39 W m−1 K−1 at 423 K. Correspondingly, an increased ZT of 0.5 at 423 K is observed in n‐type (GeTe)0.45(AgBiTe2)0.55. Furthermore, a single‐leg module demonstrates a maximum η of 6.6% at the temperature range from 300 to 500 K. This study indicates that AgBiTe2 alloying can successfully turn GeTe into n‐type with simultaneously optimized thermoelectric performance. By proper structure engineering, exotic n‐type GeTe‐based materials with hierarchical architectural structures are reported. This unique architecture can simultaneously increase electrical performance and decrease thermal performance, and demonstrating high thermoelectric conversion efficiency. The high‐performance n‐type GeTe‐based material matching well with p‐type GeTe‐based materials can promote the corresponding practical applications.