Remarkable conductivity enhancement in P-doped polythiophenes via rational engineering of polymer-dopant interactions

Molecular doping is an effective approach to tune the charge density and optimize electrical performance of conjugated polymers. However, the introduction of dopants, on the other hand, may disturb the polymer microstructure and disrupt the charge transport path, often leading to a decrease of charge carrier mobility and deterioration of electrical conductivity of the doped films. Here we show that dopant-induced disorder can be overcome by rational engineering of polymer-dopant interactions, resulting in remarkable enhancement of electrical conductivity. Benchmark poly(3-hexylthiophene) (P3HT) and its analogous random polymers of 3-hexylthiophene and thiophene P[(3HT)1-x-stat-(T)x] were synthesized and doped by 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). Remarkably, random P[(3HT)1-x-stat-(T)x] was doped to a far superior electrical conductivity, that in the case of x ≥ 0.24, the conductivity of P[(3HT)1-x-stat-(T)x] is over 100 times higher than that of the doped P3HT, despite both P3HT and P[(3HT)1-x-stat-(T)x] exhibit comparable charge carrier mobility in their pristine state and in spite of their practically identical redox properties. This result can be traced back to the formation of π-stacked polymer-dopant-polymer co-crystals exhibiting extremely short packing distances of 3.13–3.15 \uc5. The mechanism behind these performances is based on a new role played by the dopant molecules that we name “bridging-gluing”. The results are coherently verified by the combination of optical absorption spectroscopy, X-ray diffraction, density functional theory calculations, and molecular dynamics simulations

Polymères conducteurs électroniques et nanomatériaux hybrides pour le stockage de l'énergie

Dans une première partie de ce travail, nous avons préparé des nanostructures à base de polypyrrole (PPY) et de nanoparticules d'oxyde de fer, obtenues par polymérisation chimique oxydative du pyrrole en présence d'une solution aqueuse colloïdale de Fe2O3. Nous avons étudié particulièrement l'influence de la nature de l'agent dopant et de la proportion en Fe2O3 sur la morphologie des poudres et leur conductivité électrique. Les mesures de capacitances sur des électrodes à base de nanocomposites (mises en forme a partir d'un liant et en présence de noir d'acétylène) indiquent une augmentation significative des propriétés de stockage de charges pour les structures hybrides par rapport au PPY sans nanoparticules. Dans un second temps, nous avons optimisé la synthèse et effectué la caractérisation d'électrodes composites de poly 3-méthylthiophène (PMeT). Enfin nous avons examiné les performances de ces systèmes en utilisant un liquide ionique à température ambiante (1-éthyl-3-méthyl-imidazolium bis(trifluorométhylsulfonyl)Imide (EMITFSI)) comme alternative aux électrolytes liquides classiques afin d'améliorer la stabilité électrochimique et la capacité spécifique des nanocomposites.In this work, we report first on the preparation of nanostructures based on polypyrrole and iron oxide nanoparticles by oxidative polymerisation of pyrrole in colloidal solution of Fe2O3. The conductivity and the morphology of nanocomposites were studied and related to the doping agent role and the weight ratio (Fe2O3/PPy). The specific capacity measurement on the composite electrode (based on the nanocomposite, acetylene black and binders) indicate a significant enhancement of charge storage for nanocomposites compared to pure polypyrrole. Then, we investigated the synthesis and characterisation of composite electrode based on poly 3-méthylthiophène (PMeT), which depend on different methods of preparation, electrolyte and doping potential. Finally, a room temperature ionic liquid (RTIL) such as imidazolium trifluoromethanesulfonimide (EMITFSI), was used and seem to be a promising electrolyte since it increases further the capacity with a high stability during charge-discharge processes.CERGY PONTOISE-BU Neuville (951272102) / SudocSudocFranceF