High Performance Thermoelectric Power of Bi0.5Sb1.5Te3 Through Synergistic Cu2GeSe3 and Se Incorporations

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 20; no. 12; pp. e2306701 - n/a
• Main Authors: Pang, Kaikai, Yuan, Minhui, Zhang, Qiang, Li, Yanan, Zhang, Yuyou, Zhou, Wenjie, Wu, Gang, Tan, Xiaojian, Noudem, Jacques G., Cui, Chen, Hu, Haoyang, Wu, Jiehua, Sun, Peng, Liu, Guo‐Qiang, Jiang, Jun
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01-03-2024
• Subjects: Ball milling; band engineering; Bi0.5Sb1.5Te3; Copper; high performance; microstructure modulation; Modules; Power factor; Synergistic effect; Thermal conductivity; Thermoelectric materials; thermoelectric module; Waste heat recovery
• DOI: 10.1002/smll.202306701
• EISSN: 1613-6829
• ISSN: 1613-6810

Bi2Te3‐based alloys are the benchmark for commercial thermoelectric (TE) materials, the widespread demand for low‐grade waste heat recovery and solid‐state refrigeration makes it imperative to enhance the figure‐of‐merits. In this study, high‐performance Bi0.5Sb1.5Te3 (BST) is realized by incorporating Cu2GeSe3 and Se. Concretely, the diffusion of Cu and Ge atoms optimizes the hole concentration and raises the density‐of‐states effective mass (md*), compensating for the loss of “donor‐like effect” exacerbated by ball milling. The subsequent Se addition further increases md*, enabling a total 28% improvement of room‐temperature power factor (S2σ), reaching 43.6 µW cm−1 K−2 compared to the matrix. Simultaneously, the lattice thermal conductivity is also significantly suppressed by multiscale scattering sources represented by Cu‐rich nanoparticles and dislocation arrays. The synergistic effects yield a peak ZT of 1.41 at 350 K and an average ZT of 1.23 (300–500 K) in the Bi0.5Sb1.5Te2.94Se0.06 + 0.11 wt.% Cu2GeSe3 sample. More importantly, the integrated 17‐pair TE module achieves a conversion efficiency of 6.4%, 80% higher than the commercial one at ΔT = 200 K. These results validate that the facile composition optimization of the BST/Cu2GeSe3/Se is a promising strategy to improve the application of BST‐based TE modules.
The two‐step optimization strategy, which contributed to increased density‐of‐state effective mass and microstructural modulation with little loss of hole mobility, significantly promotes power factor, and suppresses thermal conductivity, yielding a peak ZT of 1.41 at 350 K and a high average ZT (300–500 K) of 1.23 in the Bi0.5Sb1.5Te2.94Se0.06+0.11 wt.% Cu2GeSe3 sample. Most impressively, by integrating the n‐type zone‐melted Bi2Te2.7Se0.3, the fabricated 17‐pair thermoelectric module demonstrate an overwhelming conversion efficiency of up to 6.4% at ΔT = 200 K.