Facile preparation of air-stable n-type thermoelectric single-wall carbon nanotube films with anionic surfactants

Thermoelectric generators based on single-wall carbon nanotubes (SWCNTs) have great potential for use in wearable and skin electronics because of their lightweight and mechanically soft structure. However, the fabrication of air-stable n-type thermoelectric SWCNTs using conventional processes is challenging. Herein, we propose a facile process for fabricating air-stable n-type SWCNT films with anionic surfactants via drop casting followed by heat treatment. We examined different surfactants (Sodium Dodecyl Sulfate, Sodium Dodecylbenzene Sulfonate, and Sodium Cholate) and heat-treatment temperatures. The optimal SWCNT film maintained the n-type Seebeck coefficient for 35 days. Moreover, to further extend the n-type Seebeck coefficient maintenance, we periodically reheated the SWCNT film with a surfactant that had returned to the p-type Seebeck coefficient. The reheated film recovered the n-type Seebeck coefficient, and the effect of the reheating treatment lasted for several reheating cycles. Finally, we elucidated a simple mechanism for realizing an air-stable n-type Seebeck coefficient based on spectroscopic analyses of the SWCNT films.