Abstract
Flexible, light-weight and robust thermoelectric (TE) materials have attracted much attention to convert waste heat from low-grade heat sources, such as human body, to electricity. Carbon nanotube (CNT) yarn is one of the potential TE materials owing to its narrow band-gap energy, high charge carrier mobility, and excellent mechanical property, which is conducive for flexible and wearable devices. Herein, we propose a way to improve the power factor of CNT yarns fabricated from few-walled carbon nanotubes (FWCNTs) by two-step method; Joule-annealing in the vacuum followed by doping with p-type dopants, 2,3,5,6-tetrafluo-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). Numerical calculations and experimental results explain that Joule-annealing and doping modulate the electronic states (Fermi energy level) of FWCNTs, resulting in extremely large thermoelectric power factor of 2250 µW m−1 K−2 at a measurement temperature of 423 K. Joule-annealing removes amorphous carbon on the surface of the CNT yarn, which facilitates doping in the subsequent step, and leads to higher Seebeck coefficient due to the transformation from (semi) metallic to semiconductor behavior. Doping also significantly increases the electrical conductivity due to the effective charge transfers between CNT yarn and F4TCNQ upon the removal of amorphous carbon after Joule-annealing.
Highlights
Www.nature.com/scientificreports nanotube (SWCNT) thin films with TE power factors in the range of 700 μW m−1 K−2 at 298 K using a combination of ink chemistry, solid-state polymer removal, and charge transfer doping strategies[15]
We propose a way to improve the TE power factor of Carbon nanotube (CNT) yarn composed of individual CNTs (FWCNTs) by a facile two-step method; Joule-annealing in the vacuum condition followed by doping with p-type dopants F4TCNQ (2,3,5,6-tetrafluo-7,7,8,8-tetracyanoquinodimethane)
After Joule-annealing at the heat amount of ~ 4 W, the Seebeck coefficient improves to 114 μV K−1 while the electrical conductivity becomes slightly lower than that of pristine one (592 S cm−1), resulting an increase in power factor from 34 to 776 μW m−1 K−2 at room temperature
Summary
Www.nature.com/scientificreports nanotube (SWCNT) thin films with TE power factors in the range of 700 μW m−1 K−2 at 298 K using a combination of ink chemistry, solid-state polymer removal, and charge transfer doping strategies[15]. Choi et al have reported large TE power factor of 2387 and 2456 μW m−1 K−2 by p- and n-type doping of double-walled carbon nanotube (DWCNT) yarn with iron chloride and polyethylenimine, respectively[13]. All these reports are based on CNT yarn composed of SWCNTs or DWCNTs9,13,15–17, which require precise control in fabrication process, and incurring high cost for mass production. We propose a way to improve the TE power factor of CNT yarn composed of individual CNTs (FWCNTs) by a facile two-step method; Joule-annealing in the vacuum condition followed by doping with p-type dopants F4TCNQ (2,3,5,6-tetrafluo-7,7,8,8-tetracyanoquinodimethane). Doping with molecular dopant significantly increases the electrical conductivity due to the effective charge transfer between CNT yarn and F4TCNQ upon the removal of amorphous carbon after Joule-annealing
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
