Organic borate doped carbon nanotube for enhancement of thermoelectric performance

Abstract

Molecular doping is vital to control the charge transport in organic/inorganic semiconductors, which provides an important technique to optimize the thermoelectric (TE) performance. Here, two organic borates with designed molecular structures, Ph3C+[B(C6F5)4]- and Ph2I+[B(C6F5)4]-, were employed as p-type dopants to enhance the TE performance of single-walled carbon nanotubes (SWCNTs). The electrons are transferred from SWCNTs to the electron-deficient cations of the borates, resulting in charge-transfer complexes stabilized by [B(C6F5)4]-. Specifically, compared to the pristine SWCNTs, the borate-doped SWCNT films reveal enhanced power factors of 135.5 ± 8.4 μW m−1 K−2 for SWCNT/Ph3C+[B(C6F5)4]-, and 156.6 ± 7.2 μW m−1 K−2 for SWCNT/Ph2I+[B(C6F5)4]-. Moreover, the p-doped SWCNTs display good air and thermal stabilities due to the chemical inertness and thermal stability of the organic [B(C6F5)4]- anions. In addition, by immersion in organic solvent, the TE performance can be further increased. This work provides a novel strategy to achieve stable p-doped SWCNT films with excellent TE performance via rational molecular design of organic borate dopants.