Highly Efficient Thermoelectricity Based on Self-Doped Carbon Nanotubes through the Repetitive Filtration Process

Area of Science:

• Materials Science
• Nanotechnology
• Energy Conversion

Background:

• Conventional thermoelectric (TE) materials research focuses on highly pure semiconducting single-walled carbon nanotubes (s-SWCNTs) with external doping.
• Achieving superior TE performance in SWCNT films has been challenging due to purity and doping limitations.

Purpose of the Study:

• To investigate the effect of minute quantities of metallic single-walled carbon nanotubes (m-SWCNTs) on the thermoelectric performance of s-SWCNT films.
• To develop a self-doping strategy for enhancing TE properties in SWCNT-based devices.

Main Methods:

• Utilized repetitive filtration (RF) processes to prepare s-SWCNT films with controlled amounts of m-SWCNTs.
• Employed spectroscopic analyses to verify film purity and characterize SWCNT states.
• Determined doping states via optical bleaching and analyzed TE device performance.

Main Results:

• RF process increased s-SWCNT purity to over 99%, reducing impurities and bundling.
• Self-doping by endogenous m-SWCNTs was observed, influenced by Fermi levels and redox environments.
• Achieved highest power factor (PF) of 8309 μW/m·K² and figure of merit (zT) of 0.17 with a Seebeck coefficient (α) of 645 μV/K.

Conclusions:

• Minute quantities of m-SWCNTs facilitate effective self-doping in s-SWCNT films.
• This strategy enhances electrical conductivity and TE performance without external dopants.
• The developed method offers a promising route for high-performance SWCNT-based thermoelectric devices.