Double doping approach for unusually stable and large n-type thermoelectric voltage from p-type multi-walled carbon nanotube mats

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 8; no. 26; pp. 1395 - 1315
• Main Authors: Hu, Qiujun, Lu, Zhongxu, Wang, Yizhuo, Wang, Jing, Wang, Hong, Wu, Ziping, Lu, Guanghao, Zhang, Hao-Li, Yu, Choongho
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 07.07.2020
• Subjects: air; ambient temperature; Benzimidazoles; carbon nanotubes; Doping; electric potential difference; encapsulation; iron; Low cost; Mats; Multi wall carbon nanotubes; Nanoparticles; Nanotechnology; Nanotubes; Organic materials; Power factor; Room temperature; Seebeck effect; Temperature gradients; Thermoelectricity
• ISSN: 2050-7488; 2050-7496; 2050-7496
• DOI: 10.1039/d0ta03247f

Multi-walled carbon nanotubes (MWCNTs) have shown low n-type Seebeck coefficients (−10 μV K −1 ), which are not good enough to prepare high performance low-cost MWCNT based mechanically flexible thermoelectric devices. Here, we present a double doping approach utilizing a small n-type doping molecule, 1,3-dimethyl-2-phenyl-2,3-dihydro-1 H -benzimidazole (N-DMBI), in addition to encapsulated metal (iron) nanoparticles for achieving a high n-type thermoelectric performance with MWCNTs. With double doping, we have shown high n-type Seebeck coefficients up to −56 μV K −1 along with a power factor up to 112 μW m −1 K −2 at room temperature, which, to the best of our knowledge, is at least an order of magnitude higher than the power factors of previously reported n-type MWCNT based organic materials. More importantly, the negative Seebeck coefficient was maintained even after 60 days' exposure to air. An outstanding output power of 1.9 W m −2 at a temperature difference of 60 K was generated with a flexible thermoelectric device made of only MWCNT mats. The new findings could lead to the development of robust and flexible thermoelectric devices made of only low-cost MWCNTs. Multi-walled carbon nanotubes (MWCNTs) have shown low n-type Seebeck coefficients (−10 μV K −1 ), which are not good enough to prepare high performance low-cost MWCNT based mechanically flexible thermoelectric devices.