Efficiently doped P3HT and polystyrene blend with porous 3D structure for thermoelectric applications

Abstract

This study describes a reproducible process for forming highly mesoporous, mechanically robust, and handleable aerogels based on entangled poly(3-hexylthiophene) (P3HT) and syndiotactic polystyrene (sPS) nanofibers for thermoelectric applications. The highly porous structure results in low thermal conductivity, allowing the temperature difference (between the hot and the cold side) to be maintained across the aerogel sample. Porosity also enables dopants to diffuse efficiently within the sample. When using 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F₄TCNQ), the highest dopant uptake leads to a maximum apparent electrical conductivity of 2 × 10⁻² S cm⁻¹ and a Seebeck coefficient (58 µV K⁻¹) close to the values obtained in thin films. The Seebeck coefficient is not affected by the high porosity of the material. To improve the doping level of the P3HT:sPS aerogels, FeCl₃ or a mixture of F₄TCNQ:FeCl₃ is also used as a dopant. This enhances the power factor (0.2 µW m⁻¹ K⁻²) without significantly increasing the thermal conductivity (30–40 mW m⁻¹ K⁻¹). Finally, the use of the doped aerogel as a vertical thermoelectric generator with one leg is demonstrated by generating a few tens of nW at a thermal difference of 11 K. This result highlights the potential for integrating these polymer aerogels into wearable thermoelectric generators for powering microelectronics.