Enhanced Flexible Thermoelectric Performance in Polymer-CNT Composites via Carbon Nanotube Alignment

Abstract

Polymer-based flexible thermoelectrics (TE) are promising materials for energy harvesting in wearable devices due to their flexibility and ability to directly convert thermal energy into electrical energy at low temperatures. Enhancing the thermoelectric efficiency without losing flexibility is important in the field of flexible thermoelectric generators. This study explores the use of single-walled carbon nanotubes (SWCNTs) in a poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE) polymer matrix. We systematically investigated the effect of SWCNT alignment on the thermoelectric properties and flexibility of the films. By applying an AC electric field during fabrication, we effectively aligned single-walled carbon nanotubes (SWCNTs) within the matrix, as confirmed by scanning electron microscopy imagery and in-plane resistivity measurements. The composite film with aligned SWCNTs showed an increase in electrical conductivity by a factor of 6 and a thermoelectric figure of merit (ZT) by approximately seven times compared to composites with randomly oriented SWCNTs. The power factor of the composite film with aligned SWCNTs decreases by 4% after 105 bending cycles compared to its initial value. The maximum output power of the composite thermoelectric generator is 321 nW. © 2025 American Chemical Society.