Boosting the thermoelectric performance of n-type Bi2S3 by hierarchical structure manipulation and carrier density optimization

• Published in: Nano energy Vol. 87; p. 106171
• Main Authors: Ji, Wenting, Shi, Xiao-Lei, Liu, Wei-Di, Yuan, Hualei, Zheng, Kun, Wan, Biao, Shen, Weixia, Zhang, Zhuangfei, Fang, Chao, Wang, Qianqian, Chen, Liangchao, Zhang, Yuewen, Jia, Xiaopeng, Chen, Zhi-Gang
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.09.2021
• Subjects: Bi2S3; Calculation; Doping; Structure; Thermoelectric; Bi2S3; Thermoelectric; Calculation; Structure; Doping
• ISSN: 2211-2855
• DOI: 10.1016/j.nanoen.2021.106171

Te-free Bi2S3-based thermoelectric materials show great potential for eco-friendly and industrial scale-up applications because of their high-abundance, low-cost, low-toxicity, and low-thermal-conductivity features. However, their low figure of merit, ZT limits their further applications. In this work, we report a high ZT of ~0.8 at ~760 K in n-type polycrystalline Bi2S3 by a combination of hierarchical structure manipulation and carrier density optimization. A step-by-step fabrication by using mechanical alloying, high-pressure and high-temperature treatment, spark plasma sintering, and annealing leads to unique micro/nanostructures in polycrystalline Bi2S3 including refined grains, high-density Bi-rich nanoprecipitates, significant lattice distortions, and nanopores that confirmed by comprehensive characterizations, which contribute to significantly suppressed lattice thermal conductivity of 0.41 W m−1 K−1 at ~760 K. A further 0.5 mol% CuCl2-doping triggers impurity band in the electronic structure of Bi2S3 and narrows the bandgap for optimizing the carrier concentration at ~1 × 1020 cm−3, confirmed by both experimental results and first-principles density functional theory calculations. The optimized carrier concentration and maintained low lattice thermal conductivity give rise to a high power factor of ~5.3 μW cm−1 K−2 and high ZT that ranks as a top value. This work provides a new route to achieve high thermoelectric performance in n-type polycrystalline Bi2S3. [Display omitted] •A record-high ZT of ~0.8 at 760 K is achieved in n-type polycrystalline Bi2S3.•CuCl2-doping triggers impurity band of Bi2S3 and narrows its bandgap.•An optimized ne of ~1 × 1020 cm−3 leads to a high S2σ of ~5.3 μW cm−1 K−2 at 760 K.•Unique micro/nanostructures significantly suppress κl to 0.41 W m−1 K−1 at 760 K.