In the context of the global developments of sustainability, waste heat conversion has become an attractive area of focus in recent years. Thermoelectric materials allow the utilization of this waste heat for generating electricity. This might help to increase industrial productivity and provide for the development of a green economy.

Japanese researchers from Okayama University have worked out a brilliant strategy for generating n-type CNT yarns. It can be beneficial for utilizing CNT resources for converting low-grade waste heat into electricity. The results published shows that the achievement of the research tackles a critical barrier to CNT-based thermoelectric devices used at temperatures below 200° C.

The team led by Research Associate Professor Hiroo Suzuki doped CNT yarns with a stable organic compound called N-DMBI using a novel solvent process. These n-type yarns can then be paired with previously developed p-type CNT yarns to create efficient, flexible thermoelectric generators.

“Constructed from CNTs, CNT yarns are well-suited for practical applications as the yarn-like structure allows for the fabrication of flexible thermoelectric devices such as fabric-based modules,” says Dr. Suzuki.


  • N-DMBI has the advantage of being small in molecular size. This allows efficient doping in an unexpectedly short time of 10 seconds.
  • It also offers air and high-temperature stability up to 150 °C.
  • Joule annealing of the yarns further significantly improves their n-doping efficiency.
  • The yarns achieved exceptional thermoelectric performance metrics, with a power factor of 2800, 2390, and 1534 µW m-1 K-2 at 200, 150, and 30 °C, respectively.
  • For low temperatures, o-dichlorobenzene is the most suitable solvent for N-DMBI doping.
  • A prototype flexible π-type module could produce electricity at just 55° C with a 20° C temperature difference.

“Achieving power generation at low temperatures with small temperature differences is significant for the development of thermoelectric modules that can tap into various thermal sources, such as waste heat from industrial facilities, thermal dissipation from vehicles, and even body heat,” says Dr. Suzuki.

Find out NIST Research team Explored a novel heat to electricity conversion method.

By enabling high-performance CNT yarn thermoelectric generators that can operate with just small thermal differences like body heat. The research that highlighting carbon nanotube yarn has potential to harvest waste heat paves the way for innovative technologies. These could provide local power for wearable devices, IoT sensors, and other applications while reducing wasted energy.

Source: N-DMBI Doping of Carbon Nanotube Yarns


Elliot is a passionate environmentalist and blogger who has dedicated his life to spreading awareness about conservation, green energy, and renewable energy. With a background in environmental science, he has a deep understanding of the issues facing our planet and is committed to educating others on how they can make a difference.

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