Study and development of sustainable functional organic thermoelectric materials for applications in automotive

In this thesis, I synthesized, characterized, and formulated novel p-n conjugated and semiconducting polymers designed for thermoelectric and photovoltaic applications. Conducted in synergy with Martur Fompak International srl, the work bridges molecular design, synthetic chemistry, and functional device engineering, highlighting scalable processing and compatibility with flexible, porous substrates, laying a foundation for next-generation energy materials. Initial efforts were dedicated to poly(3-hexylthiophene) (P3HT), synthesized via oxidative polymerization. Post-doping with FeCl3 and I2 demonstrated tunable conductivity; however, environmental stability posed significant challenges over time. Advanced spectroscopic methods, including UV-Vis-NIR and FTIR-ATR, effectively tracked charge carrier formation, providing crucial insights into real-time doping dynamics. In parallel, I developed coordination polymers with etenetetrathiolate ligands, specifically Ni- and Cu-based systems such as poly[Kₓ(Niett)] and poly[Kₓ(Cu(I)ett)]. Their intrinsic insolubility complicated processing: nonetheless, innovative dispersion strategies enabled successful film formation, thickness control and promising device integration. Thermoelectric evaluations identified poly[Kₓ(Niett)] as the most promising n-type polymer, exhibiting Seebeck coefficients around -100 μV/K at 30 °C. Optimizing reaction conditions, including temperature, reaction time, oxidant, and solvent, aimed at enhancing process efficiency and reducing costs. Preliminary studies indicated micellar synthesis as a cost-effective, sustainable approach, although residual surfactants reduced conductivity and yield, necessitating further investigation. Conversely, p-type polymers, as poly[Kₓ(Cu(I)ett)], showed excellent thermoelectric performance, reaching approximately 3 S/cm conductivity and a Seebeck coefficient arpund 60 μV/K at room temperature. A functional p-n asymmetric thermoelectric planar module demonstrated an overall Seebeck coefficient close to 200 μV/K, effectively validating theoretical predictions. This module exhibited consistent performance on flexible PET substrates, underscoring the polymers’ adaptability. The versatility of these materials was further illustrated by their successful deposition on cellulose-based substrates, resulting in flexible, freestanding thermoelectric coatings. Moreover, polyurethane foams functionalized with conductive polymers, including P3HT, PEDOT:PSS, poly[Kₓ(Niett)], and poly[Kₓ(Cu(I)ett)], presented promising pathways for automotive applications. Additionally, coordination polymers were evaluated as catalysts in dye-sensitized solar cells exhibiting remarkable efficiency. Poly[Kₓ(Niett)] counter electrodes reached power conversion efficiencies exceeding 10% under standard illumination, maintaining high performance under low-light conditions due to stable catalytic activity and effective charge transport. Overall, these innovative polymeric materials open new avenues for sustainable energy recovery, with significant potential in thermoelectrics and photovoltaics.