Femtosecond Fluorescence Upconversion Study of a Naphthalimide–Bithiophene–Triphenylamine Push–Pull Dye in Solution

Valentin Maffeis 1 Romain Brisse 1 Vanessa Labet 2 Bruno Jousselme 1 Thomas Gustavsson 3, 4
1 LICSEN - Laboratoire Innovation en Chimie des Surfaces et NanoSciences
NIMBE UMR 3685 - Nanosciences et Innovation pour les Matériaux, la Biomédecine et l'Energie (ex SIS2M)
4 DICO - Biomolécules Excitées
IRAMIS - Institut Rayonnement Matière de Saclay, LIDyl - Laboratoire Interactions, Dynamique et Lasers (ex SPAM)
Abstract : There is a high interest in the development of new push-pull dyes for the use in dye sensitized solar cells. The pronounced charge transfer character of the directly photo-excited state is in principle favorable for a charge injection. Here, we report a time-resolved fluorescence study of a triphenylamine-bithiophene-naphthalimide dye in four solvents of varying polarity using fluorescence upconversion. The recording of femtosecond time-resolved fluorescence spectra corrected for the group velocity dispersion allows for a detailed analysis discriminating between spectral shifts and total intensity decays. After photoexcitation, the directly populated state (S1/FC), evolves towards a relaxed charge transfer state (S1/CT). This S1/CT state is characterized by a lower radiative transition moment and a higher non-radiative quenching. The fast dynamic shift of the fluorescence band is well described by solvation dynamics in polar solvents, but less so in non-polar solvents, hinting that the excited state relaxation process occurs on a free energy surface whose topology is strongly governed by the solvent polarity. Finally, the highly stabilized S1/CT state undergoes a fast non-radiative quenching. This study underlines the influence of the environment on the intramolecular charge transfer (ICT) process, and the necessity to analyze time-resolved data in detail when solvation and ICT occur simultaneously.
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https://hal-cea.archives-ouvertes.fr/cea-01817447
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Submitted on : Monday, June 18, 2018 - 8:17:57 AM
Last modification on : Wednesday, July 31, 2019 - 2:56:05 PM

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Valentin Maffeis, Romain Brisse, Vanessa Labet, Bruno Jousselme, Thomas Gustavsson. Femtosecond Fluorescence Upconversion Study of a Naphthalimide–Bithiophene–Triphenylamine Push–Pull Dye in Solution. Journal of Physical Chemistry A, American Chemical Society, 2018, 122, pp.5533-5544. ⟨https://doi.org/10.1021/acs.jpca.8b05177⟩. ⟨10.1021/acs.jpca.8b05177⟩. ⟨cea-01817447⟩

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