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Structure and Dynamics of conjugated polymers : A combined approach of quasielastic neutron scattering, wide-angle x-ray diffraction and atomistic simulations

Mercredi 18 décembre 2013 11:00 - Duree : 1 heure
Lieu : Conference Room, ILL4 - 6 rue Jules Horowitz - Grenoble

Orateur : Dr. Anne A. Y. GUILBERT (Department of Chemical Engineering and Centre for Plastic Electronics, Imperial College London, United Kingdom)

Nowadays, the best performing designs of organic solar cells are based on blend films of a conjugated polymer and a fullerene derivative. The performance of such devices is strongly related to the blend microstructure. Therefore, in the selection of new semiconductor materials for improved light harvesting or higher photovoltage, it is essential to understand the effect of chemical structure on microstructure and on its evolution in time since most of the common conjugated polymers exhibit a glass transition temperature around room temperature. In this work, we use an approach combining computations (quantum chemistry and molecular dynamics (MD) ) and experiments (quasi-elastic neutron scattering (QENS) and grazing incidence wide-angle X-Ray diffraction (GIWAXS)). First, I will present a study of the dynamics of poly(3-hexylthiophene-2.5-diyl) P3HT and poly(3-octylthiophene-2.5-diyl) P3OT, in bulk, by combining QENS and MD. The targeted quantities are the activation energy and the relaxation times of the different motions of the polymers. This is particularly relevant to the understanding of, on one hand, the results of post-annealing treatment, and on the other, lifetime of organic solar cells by correlating operation temperature and time with motion of the polymer. Second, an ab-initio method to predict crystal polymorphisms will be presented. The results of these simulations are then compared with the GIWAXS data of poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b’]dithiophene-2,6-diyl]] (C-PCPDTBT) thin films and its analogue Si-PCPDTBT1, where the carbon bridging atom between the backbone and the side chains has been substituted with a silicon atom impacting considerably the crystal structure and crystallinity of this material. Thus influencing the performances of the organic solar cells. Finally, the GIWAXS data on 3-helythiophene-2,5-diyl 3HT oligomers of different lengths - that show a transition between two polymorphs depending on the oligomer length2 – is compared with the predictions. 1 Guilbert et al., submitted to Chem. Mater. 2 Koch et al., JACS, 2013, 135,13699-13709

Contact : tellier@ill.fr

Discipline évènement : (Physique)
Entité organisatrice : (ILL)
Nature évènement : (Séminaire)
Evènement répétitif : (General ILL Seminar - College 7)
Site de l'évènement : Polygone scientifique

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