High thermoelectric figure of merit of porous Si nanowires from 300 to 700 K

• Published in: Nature communications 2021-06, Vol.12 (1), p.3926-7, Article 3926
• Main Authors: Yang, Lin, Huh, Daihong, Ning, Rui, Rapp, Vi, Zeng, Yuqiang, Liu, Yunzhi, Ju, Sucheol, Tao, Yi, Jiang, Yue, Beak, Jihyun, Leem, Juyoung, Kaur, Sumanjeet, Lee, Heon, Zheng, Xiaolin, Prasher, Ravi S.
• Format: Article
• Language: English
• Subjects: 140/58; 142/126; 147/135; 147/143; 639/4077/4107; 639/925/357/1016; Ambient temperature; Cost effectiveness; Cryogenic temperature; Crystallites; Crystals; Electrical conductivity; Electrical resistivity; Figure of merit; High temperature; Humanities and Social Sciences; MATERIALS SCIENCE; multidisciplinary; Nanotechnology; Nanowires; Operating temperature; Porous silicon; Science; Science (multidisciplinary); Seebeck effect; Silicon; Synthesis; Thermal conductivity; thermoelectric devices and materials; Thermoelectricity; Waste heat
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-021-24208-3

Thermoelectrics operating at high temperature can cost-effectively convert waste heat and compete with other zero-carbon technologies. Among different high-temperature thermoelectrics materials, silicon nanowires possess the combined attributes of cost effectiveness and mature manufacturing infrastructures. Despite significant breakthroughs in silicon nanowires based thermoelectrics for waste heat conversion, the figure of merit ( ZT ) or operating temperature has remained low. Here, we report the synthesis of large-area, wafer-scale arrays of porous silicon nanowires with ultra-thin Si crystallite size of ~4 nm. Concurrent measurements of thermal conductivity ( κ ), electrical conductivity ( σ ), and Seebeck coefficient ( S ) on the same nanowire show a ZT of 0.71 at 700 K, which is more than ~18 times higher than bulk Si. This ZT value is more than two times higher than any nanostructured Si-based thermoelectrics reported in the literature at 700 K. Experimental data and theoretical modeling demonstrate that this work has the potential to achieve a ZT of ~1 at 1000 K. Performance of Si nanowires as thermoelectrics are evaluated only from cryogenic to ambient temperatures and ZT has remained low. Here, the authors systematically optimized the synthesis method and improved the suspended microdevice platform to achieve high-performance thermoelectrics up to 700 K.