Simple fabrication of single-walled carbon nanotube films and electrical property control via nitrosonium salt doping

In this study, we developed a simple process for fabricating free-standing single-walled carbon nanotube (SWCNT) films without centrifugation, using only ultrasonic treatment in o-dichlorobenzene and vacuum-filtration. The electrical and thermoelectric properties of the resulting SWCNT films were evaluated. Chemical doping with nitrosonium salts (NOPF6, NOBF4, and NOSbF6) significantly enhanced the electrical conductivity, achieving an improvement of up to approximately three-fold. X-ray photoelectron spectroscopy confirmed that doping induced a charge-transfer-type p-doped state in the materials. Although the Seebeck coefficient decreased upon doping, resulting in a reduced power factor, this behavior can be understood as a typical tradeoff caused by the increased carrier density of the doped samples. Furthermore, the chemically doped SWCNT films exhibited excellent durability, with minimal changes in their electrical properties even after six months of storage in nitrogen. These findings demonstrate that a simple film fabrication method combined with chemical doping can yield highly conductive and long-term stable SWCNT films, providing valuable insights into the design of conductive materials based on SWCNTs.