High-performance chalcogenide-based thermoelectric films and devices for self-powered flexible electronics

Title : High-performance chalcogenide-based thermoelectric films and devices for self-powered flexible electronics

Abstract:

Thin-film thermoelectric (TE) generators and coolers present promising solutions for self-powering of wearable electronics and thermal dissipation of chips, respectively. The advancement of high-performance, flexible TE films is crucial for the widespread applications of thin-film TE devices. In recent years, chalcogenide-based TE materials, including Ag₂Se and Bi₂Te₃, have garnered ever-increasing attention due to their exceptional TE performance near room temperature. However, their brittleness and rigidity are far-flung and agelong challenges for flexible applications. To address this issue, we developed bottom-up and top-down approaches to prepare Ag₂Se and Bi₂Te₃-based films with high TE properties and good flexibility. The effects of composition and microstructure on TE properties and flexibility were investigated. Additionally, we assembled thin-film devices with optimized structure.

The “bottom-up” approach was employed to prepare inorganic TE films, utilizing atoms, ions, or molecules as the “building blocks”. Through this method, a range of Ag₂Se-based films were fabricated via a process involving chemically template-assisted synthesis, vacuum filtration, and subsequent hot-pressing. Notably, the Ag₂Se/MXene composite film exhibited a high power factor of 2100 mW m^-1 K^-2 at 300 K. A Bending test demonstrated the exceptional flexibility of this hybrid film. The as-assembled flexible TE device generated a maximum power density of 24.2 W m^-2 at a temperature difference of 30 K. Additionally, multifunctional TE devices with rapid responsiveness hold great potential as wearable/portable energy supply, cooler and sensor applications.

The “top-down” method involves the fabrication of bulks by traditional melting and annealing processes, followed by slicing or exfoliating into thin sheets or nanosheets. Employing this technique, we demonstrated the good pliability of 1000 bending cycles and high power factors of 4200 (p-type) and 4600 (n-type) mW m^-1 K^-2 in Bi₂Te₃-based films that were exfoliated from corresponding single crystals. This unprecedented bendability in single crystal films was ascribed to the in-situ observed staggered-layer structure that was spontaneously formed during the fabrication to promote stress propagation whilst maintaining good electrical conductivity. Our flexible generator showed a high normalized power density of 321 W m^-2 with a temperature difference of 60 K, surpassing other reported film-based TE devices by an order of magnitude. These high performances in supple TE films not only offer useful paradigms for wearable electronics, but also provide crucial insights into structure-property manipulation in semiconductors.

Biography:

Dr. Yao Lu graduated from Tongji University with a Ph.D degree in 2019. She is now an Assistant Professor and Ph.D. supervisor at the School of Microelectronics, Southern University of Science and Technology (SUSTech), Shenzhen, China. Her research focus on new energy conversion technology, self-powered intelligent wearable electronics, and thermoelectric cooling for on-chip thermal management. She has published over thirty SCI papers as the first author or corresponding author in prestigious journals, such as Nat. Nanotech. (ESI highly cited), Energy Environ. Sci. (ESI highly cited, hot paper), Mater. Today Phys., and J. Mater. Chem. A. She serves as a youth editorial board members of the Materials Futures and Materials Lab journals, and has been invited to review for renowned SCI journals, including Nat. Commun., Energy Environ. Sci., and J. Mater. Chem. A.