Revisiting the Vibrational and Optical Properties of P3HT: A Combined Experimental and Theoretical Study

Léa Farouil 1, 2 Fabienne Alary 1 Eléna Bedel-Pereira 2 Jean-Louis Heully 1
1 PTC - Photochimie théorique et computationnelle (LCPQ)
LCPQ - Laboratoire de Chimie et Physique Quantiques
2 LAAS-MPN - Équipe Matériaux et Procédés pour la Nanoélectronique
LAAS - Laboratoire d'analyse et d'architecture des systèmes
Abstract : We demonstrate that DFT-based calculations can provide straightforward means to analyze the effect of aggregation on the optical properties of regioregular P3HT oligomers of different lengths (up to 20-mers) and of bioligomers of 8-mers in two different conformations. Our conclusions substantially differ from those obtained previously by applying the exciton model. Indeed, analysis of Huang–Rhys factors has evidenced that two vibrational modes, a collective mode and an effective mode, are combined in the vibronic structure of the absorption spectrum of oligothiophene. Computed spectra match perfectly their experimental counterparts provided we consider that the oligomer and at least the five lowest excited states of bioligomers behave as absorbers, and that both oligomer and bioligomer contribute to the emission spectra. Study of the nature of the Franck–Condon excitation and optimization of the five lowest excited singlet states indicate that high (hot) excited states of the bioligomer may play an important role in the initiation of charge separation and highlight the importance to take into account the relaxation processes in the theoretical modeling of emission properties.
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Journal articles
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https://hal.archives-ouvertes.fr/hal-01873591
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Submitted on : Thursday, September 13, 2018 - 2:20:56 PM
Last modification on : Friday, January 10, 2020 - 9:10:15 PM

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Léa Farouil, Fabienne Alary, Eléna Bedel-Pereira, Jean-Louis Heully. Revisiting the Vibrational and Optical Properties of P3HT: A Combined Experimental and Theoretical Study. Journal of Physical Chemistry A, American Chemical Society, 2018, 122 (32), pp.6532-6545. ⟨10.1021/acs.jpca.8b03814⟩. ⟨hal-01873591⟩

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