Enhanced thermoelectric performance of PEDOT:PSS/SWCNT/PDDA three-component composite films

Abstract

Conducting polymer/carbon nanocomposites represent a promising class of materials for flexible thermoelectrics, offering advantages such as low cost, solution processability, and low thermal conductivity. However, their performance is limited by high interfacial contact resistance at carbon nanomaterial junctions, which impedes charge transport and reduces electrical conductivity. To overcome this challenge, we employ poly(diallyldimethylammonium chloride) (PDDA) as a multifunctional interfacial architect, strategically designed to electrostatically bridge PEDOT:PSS and SWCNTs. Its role extends beyond dispersion to actively modulating energy filtering, reducing tunnelling barriers, and templating a favorable morphological landscape for charge transport. These morphological improvements facilitate efficient electron transport by reducing inter-nanotube junction resistance. This reduction in resistance enhances electrical conductivity while the refined interfaces simultaneously boost the Seebeck coefficient through energy-filtering effects, leading to a synergistic improvement in the power factor. The composite films, fabricated via layer-by-layer spray coating and mild annealing (100 °C, 10 minutes), achieved a remarkable electrical conductivity of 771 ± 45 S cm⁻¹ and a Seebeck coefficient of 78 ± 9 µV K⁻¹ at 55% PDDA, yielding a high power factor of 472 ± 40 µW m⁻¹ K⁻². This work demonstrates that rational interfacial molecular design, rather than complex multi-layer structuring, is the key to unlocking high thermoelectric performance in organic composites. Our study provides a mechanistic blueprint for interface engineering, paving the way for the scalable production of efficient and flexible energy harvesting devices.