Enhanced Thermoelectric Performance in SWCNTs/PEDOT Composites via Oxidant-Controlled Conjugation

Flexible thermoelectric materials are increasingly critical for flexible electronics applications, where the composite strategy combining carbon nanotubes with conducting polymers can leverage the advantages of individual components to achieve excellent thermoelectric performance and favorable processability. In PEDOT-based composites, conjugation length is a key factor influencing thermoelectric performance, yet systematic studies on how oxidant selection governs conjugation length and subsequently affects the thermoelectric properties of the three SWCNTs/PEDOT composite films remain limited. This work systematically compares three oxidants (Fe(Tos)3, FeCl3, Na2S2O8) in vapor-phase polymerization to fabricate SWCNTs/PEDOT composites, establishing that oxidant selection deterministically controls PEDOT conjugation length and oxidation level. Multimodal spectroscopic analysis reveals that Fe(Tos)3 produces PEDOT with the longest conjugated chains. The incorporation of SWCNTs synergistically enhances electrical conductivity and Seebeck coefficient through a dual mechanism. Specifically, the composite film polymerized with Fe(Tos)3 as the oxidant exhibits a power factor more than six times greater than that of the pristine PEDOT-Tos. Furthermore, post-treatment with hydrazine dedoping further optimizes the thermoelectric performance. The resulting composite films retain over 87% of their initial performance under repeated bending tests, demonstrating good mechanical stability. This conjugation-length control strategy provides an effective route for developing high-performance flexible thermoelectric materials.