Surfactant-Mediated Control of Polyethylenimine Dopant for Enhanced Thermoelectric Performance of Carbon Nanotube Buckypaper for Varied Device Configurations

Carbon nanotubes (CNTs) are promising materials for flexible p-type applications but require chemical doping to achieve n-type properties. Using surfactants is essential to preventing agglomeration, which can affect surface properties and dopant interaction. This research investigates the influence of surfactant on the thermoelectric properties of polyethylenimine (PEI)-doped CNT buckypaper. Two buckypaper variants were prepared: one with chloroform as the solvent and the other with a surfactant and deionized water. The study revealed that the use of a surfactant along with PEI dopants prevents environmental p-type doping from oxygen molecules. The thermoelectric evaluations revealed a notable improvement in the performance of surfactant-treated buckypapers compared with their counterparts without surfactant. In essence, this research underscores the pivotal role of surfactants in shaping the thermoelectric properties of the CNT buckypapers. The module of a thermoelectric device having 60 pairs of p-n segments with dimensions 2 cm × 0.5 cm showcased a substantial output of ∼31.61 mV and ∼482.02 nW at a temperature gradient of 40 K. Furthermore, practical demonstrations conducted in this study highlight the utility of these thermoelectric devices in harnessing waste heat from everyday low-temperature heat sources such as human body. This research underscores the critical role of surfactants in shaping the thermoelectric properties of CNT buckypaper.