Engineering doping level for enhanced thermoelectric performance of carbon nanotubes/polyaniline composites

Thermoelectric (TE) properties of pure polyaniline (PANI) have been extensively investigated and significant progress has been achieved with proper modulation of doping level, there is however few reports to illustrate the crucial role of doping level in modulating the microstructure and optimizing the TE performance of carbon nanotubes (CNTs)/PANI composites. Herein, a series of CNTs/PANI composites with varied CNTs loadings are doped with various amount of camphorsulfonic acid to control doping level of PANI. As the doping level decreases, PANI chains are transformed from extended coil with delocaliztion polarons to compact with polarons localized. All the CNTs/PANI composites exhibit increased Seebeck coefficient, while show less deteriorated conductivity compared with pure PANI film. With high CNTs loading more than 69 wt%, greatly enhanced power factor of 321 ± 24 μW m−1 K−2 could be achieved at low doping level, ascribing to not only strong π-π interaction and doping effect of CNTs which promote PANI chains ordered stacking, but also intrinsic conductive CNTs network which provides extra pathways to facilitate carrier transport. This work demonstrates the effective strategy of precise tuning doping level to improve TE properties of CNTs/PANI composites.