Flexible and printable thermoelectric films based on FeCl3 doped P3HT

Conductive polymers possess several advantageous properties, including cost-effectiveness, non-toxicity, and low thermal conductivity, making them promising candidates for thermoelectric (TE) applications. In this study, flexible films of poly (3-hexylthiophene) (P3HT) doped with FeCl3 were synthesized via the drop-casting method using FeCl3 concentrations of 20, 40, and 60 mM. The structural, morphological, and thermoelectric properties of the doped P3HT films were systematically investigated. Characterization techniques such as XRD, FTIR, and Raman spectroscopy revealed significant microstructural changes upon doping. XRD analysis indicated a transition from a crystalline to a more amorphous structure, while FTIR and Raman spectroscopy confirmed the formation of localized states through shifts in vibrational modes. SEM and AFM analyses demonstrated substantial morphological changes with FeCl3 doping, and XPS confirmed the successful incorporation of FeCl3 into the P3HT matrix. Thermoelectric measurements showed a notable enhancement in electrical conductivity, increasing from 4.37 × 10−4 S/cm (undoped film) to 46.67 S/cm for the P40-doped film at room temperature. The P40 sample also exhibited a high Seebeck coefficient of 164 µV/K and achieved a maximum power factor of 127.4 µW/m·K2. These results highlight the potential of FeCl3 doping in enhancing thermoelectric performance. The freestanding flexible P3HT films displayed a significantly high p-type Seebeck coefficient, emphasizing their suitability for thermoelectric applications. Future work should aim at optimizing doping conditions and exploring the integration of these materials into practical thermoelectric devices.