Effect of Doping and Molecular Weight on the Thermal Conductivity of Conjugated Polymers for Thermoelectrics
Date: Wednesday, 30 October 2024
Time: 3PM
Venue: Institut de Ciència de Materials de Barcelona (ICMAB, CSIC) - Sala d'Actes Carles Miravitlles
Abstract
Conjugated polymers are attractive for flexible electronics and organic photovoltaics due to their lightweight and flexible nature. They are also considered promising for thermoelectric applications due to their low thermal conductivity and reasonable Seebeck coefficients. Enhancing their electrical conductivity to improve thermoelectric efficiency has been a major research focus, with efforts involving doping optimization and novel dopants. However, the relationship between doping, morphological changes, and thermoelectric properties, especially thermal conductivity, has received less attention due to the complex microstructures and the influence of factors like processing conditions and molecular weight.
In this thesis, we investigate the impact of doping, molecular weight blending, and polymer length on the morphology and thermoelectric properties of conjugated polymers, focusing on thermal conductivity. Our findings show that doping reduces the out-of-plane thermal conductivity in polymers with high structural order. This is explored through hypotheses such as increased thermal anisotropy, changes in the crystalline-to-amorphous ratio, and alloying effects. Structural analysis using GIWAXS, Raman, and infrared spectroscopy demonstrated the influence of backbone alignment on thermal transport.
Further studies on molecular weight blending in P3HT revealed its impact on both microstructure and thermal/electrical transport in doped and pristine samples. We also analyzed the effect of molecular length using seven synthesized oligomers, correlating morphological changes to thermal and electrical transport. Finally, temperature-dependent measurements provided insights into how molecular weight influences thermal conductivity at different temperatures.
In conclusion, this thesis demonstrates how doping, molecular weight, and morphology intricately affect the thermoelectric properties of conjugated polymers.
Supervisors
Mariano Campoy-Quiles
Juan Sebastián Reparaz
PhD comitee
President: Dr. Olga Caballero Calero, IIMN, Spain
Secretary: Dr. Esther Barrena Villas, ICMAB, Spain
Vocal: Prof. Oliver Fenwick, Queen Mary University of London, UK
University: Universitat Autònoma de Barcelona (UAB)
PhD Programme: Material Science
