[ca] Els polímers conjugats són materials prometedors per a l'electrònica flexible i la fotovoltaica orgànica per la seva lleugeresa, flexibilitat i rendibilitat. En l'àmbit de la conversió de calor en electricitat, es consideren materials termoelèctrics prometedors gràcies a la seva baixa conductivitat tèrmica i bons coeficients de Seebeck. Millorar la conductivitat elèctrica dels polímers conjugats ha estat un objectiu de recerca clau, centrant-se en el dopatge i la síntesi de nous dopants. Tanmateix, la correlació entre el dopatge, els canvis morfològics i les propietats termoelèctriques, especialment la conductivitat tèrmica, ha rebut poca atenció fins ara. Aquesta tesi investiga l'impacte del dopatge, la barreja de pesos moleculars i la longitud molecular en la morfologia i les propietats termoelèctriques dels polímers conjugats, amb especial èmfasi en la conductivitat tèrmica. Els resultats mostren que el dopatge redueix la conductivitat tèrmica en polímers amb alt ordre estructural, suggerint una major anisotropia tèrmica i canvis en la fracció cristal·lina a amorfa. També s'ha demostrat que l'escurçament de la columna vertebral del polímer afecta significativament la conductivitat tèrmica. A més, es va estudiar l'impacte del pes molecular mitjà en la morfologia i el transport tèrmic i elèctric, barrejant P3HT amb diferents pesos moleculars. Es va investigar la correlació entre la microestructura, el dopatge i les conductivitats tèrmica i elèctrica. També es va estudiar l'impacte de la longitud molecular del polímer en la morfologia i les propietats de transport utilitzant oligòmers de diferents longituds. En conclusió, aquesta tesi demostra com el dopatge afecta les propietats termoelèctriques dels polímers conjugats, destacant la relació entre el pes molecular, la morfologia, la temperatura i el transport tèrmic.

[en] Conjugated polymers are promising materials for flexible electronics and organic photovoltaics due to their lightweight, flexible nature, and cost-effectiveness. In the field of heat-to-electricity conversion, conjugated polymers are being extensively considered as promising thermoelectric materials due to their intrinsically low thermal conductivity and reasonable Seebeck coefficients. Enhancing the electrical conductivity towards efficient thermoelectrics based on conjugated polymers has been the focus of significant research efforts, including fine optimization through extensive studies on doping processing techniques and synthesis of novel efficient dopants. However, a comprehensive understanding of the correlation between the doping, doping-introduced morphological changes, and the resulting thermoelectric properties-particularly thermal conductivity-has received relatively limited attention thus far. This is, in part, due to the complex microstructures exhibited by conjugated polymer thin films, and its dependency on factors such as processing steps and material properties (e.g. molecular weight). In this thesis, we comprehensively investigate the impact of doping, molecular weight blending and molecular length on the morphology and the resulting thermoelectric properties of conjugated polymers, with a particular focus on thermal conductivity. The first set of results reports on the impact of doping on thermal conductivity based on eight polymers and four doping systems. We observed that upon doping, the out-of-plane component of the thermal conductivity of five polymers with relatively high structure order is reduced compared to the corresponding value for the neat polymers. We investigated several hypotheses to understand this behavior: (i) an increase in intrinsic thermal anisotropy due to in-plane orientation of the backbones, (ii) a modification in the crystalline to amorphous fraction, and (iii) an alloying effect resulting from the introduction of the dopant. Through various structural analysis techniques, including Grazing Incidence Wide Angle X-Ray (GIWAXS), Raman and infrared spectroscopy, we correlated structural and thermal properties, demonstrating a direct influence of in-plane alignment of their backbones on both the in-plane and out-of-plane components of thermal conductivity. Furthermore, through specifically designed experiments based on photolysis reaction, we demonstrated that the shortening of the polymer's backbones significantly impacts thermal conductivity. Therefore, the subsequent chapter centered on the impact of average molecular weight on morphology and the resultant thermal and electrical transport within polymers. By blending P3HTs with two different molecular weights in distinct ratios, we first investigated the impact of molecular weight on the microstructure and thermal transport in the pristine samples. Following this, we characterized the thermoelectric performance of the doped samples as a function of molecular weight. The correlation between the microstructure, doping, thermal conductivity and electron conductivity is discussed in this chapter. In the following chapter, we studied the impact of polymer molecular length on morphology and the resulting thermal and electrical transport properties using seven synthesized oligomers with gradually increasing molecular lengths. GIWAXS, photoluminescence, and UV-Vis spectroscopy were utilized to establish morphological changes across the various molecular lengths. An imaging approach was employed to accurately assess the overall homogeneity of thermal conductivity across different positions within the samples. Additionally, building on the room-temperature data of oligomers, we extended our study to temperature-dependent measurements. Consequently, we characterized the temperature-dependent thermal conductivity as a function of molecular weight and analyzed the morphological changes across different temperatures using PL. In conclusion, this thesis demonstrates the effects of doping on the thermoelectric properties of conjugated polymers and highlights the intricate relationships between molecular weight, morphology, doping, temperature, and thermal transport.