Millorant el rendiment dels termoelèctrics orgànics
- Autores: Osnat Zapata Arteaga
- Directores de la Tesis: Mariano Campoy Quiles (dir. tes.)
- Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2021
- Idioma: español
- Tribunal Calificador de la Tesis: Clara M. Gómez Clarí (presid.), Carmen Ocal Garcia (secret.), Simone Fabiano (voc.)
- Programa de doctorado: Programa de Doctorado en Ciencia de Materiales por la Universidad Autónoma de Barcelona
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
In the current Internet of Things (IoT) era, smart sensing-devices are changing much about the world we live in, from how we sense our surroundings to the way we spend energy. On-site power generators for such devices will be essential, especially if they are maintenance-free, flexible, cheap, printable, or even disposable. Organic thermoelectric materials — semiconductors that can transform heat into electricity at near-room temperature — can fulfill these characteristics. Nevertheless, there are still issues in the current state-of-the-art materials that need improvement, such as the thermoelectric performance, benchmarked by the dimensionless ZT, and the thermoelectric stability under continuous thermal stress.
This thesis reports on strategies to improve thermoelectric efficiency and stability. As a testbed material system, we employ PBTTT doped with the molecular acceptor F4TCNQ. As a transversal tool for our studies, we developed high-throughput fabrication and characterization methods based on annealing-, doping- and thickness-gradients to study and correlate the relationship between microstructure, thermoelectric properties, and stability for many samples.
The first set of results reports on a strategy to improve thermoelectric stability. We demonstrate that the formation of charge transfer complexes (CTCs) leads to more thermally enduring samples, although less electrically conductive. By developing a method to adjust the partial to integer charge-transfer ratio, we can improve the long-term stability without sacrificing the electrical conductivity.
The subsequent chapter centers on the relationship between crystallinity and thermal and electric transport. We demonstrate that the degree of crystallinity largely determines the thermal conductivity of the film. Upon doping, even a relatively small dopant content increases the electrical conductivity several orders of magnitude but lowers the thermal conductivity without noticeable deterioration in the crystallinity.
In the final chapter, we focus on a simple yet effective technique to simultaneously enhance the electrical conductivity and Seebeck coefficient. By using a matrix of PBTTT and adding small fractions of other polymers, such as RR-P3HT, we can enhance the order and microstructure quality of the film, improving the charge transport characteristics.
While centered on a particular polymer and dopant combination, our results stretch the current knowledge of the relationship between the microstructure, thermal-electric transport, and stability.
