Role of Conductive Fillers in Organic Polymer Composites for Thermoelectric Properties Near Room Temperature

This study systematically investigates the thermoelectric (TE) performance of poly(3-hexylthiophene) (P3HT)-based composite pellets doped with dodecylbenzenesulfonic acid (DBSA), focusing on the effects of different conductive fillers and the role of an inorganic spacer. Initially, graphene nanoplatelets (GNPs) were incorporated into the DBSA-doped P3HT matrix at a filler-to-polymer volume ratio of 1: 2 to optimize as a reference case. Building on these findings, additional composites were prepared at a 1: 4 filler-topolymer ratio, including GNP:P3HT(DBSA) and GNPs combined with 10 wt% TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> nanoparticles (NPs). To examine the impact of substituting conductive fillers, silver nanowires (AgNWr) were introduced as an alternative to GNPs at the same 1:4 ratio, with and without 10 wt% TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> NPs. All composites were processed into cylindrical pellets and analyzed using a vertical TE measurement setup. Key parameters, including the Seebeck coefficient, electrical conductivity, and power factor (PF), were evaluated near room temperature. The addition of TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> NPs consistently enhanced TE performance across both filler systems, acting as an effective spacer to regulate interfacial charge transport. Among all configurations, the AgNWr+10% TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>: P3HT(DBSA)(1:4) composite achieved the highest power factor of 430 nW/mK<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>. This comparative study highlights the synergistic role of DBSA as a dopant and TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> NPs as a spacer, demonstrating the potential of AgNWr-based printable composites for flexible, low-cost TE energy harvesting applications.