Exciton-exciton annihilation as a probe of exciton diffusion in large porphyrin nanorings

Giovanni Bressan, Michael Jirasek, Harry L. Anderson, Ismael A. Heisler, Stephen R. Meech

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The photophysical behavior of natural and artificial cyclic supramolecular structures has been intensively investigated in the past decade. Among the artificial structures, large fully π-conjugated porphyrin nanorings are of particular interest because of their electronic, structural, and topological features, which make them suitable candidates for light-harvesting applications. A number of factors affect the efficiency with which such structures harvest and transmit energy. For instance, under intense irradiation conditions, the efficiency of light harvesting can be quenched by competing processes, such as exciton–exciton annihilation. Here, we investigate the pump fluence dependence of the transient absorption spectra of a series of porphyrin nanorings ranging in circumference between 13 and 52 nm (10–40 porphyrin units). This allowed the isolation of a fluence-dependent fast-decaying component in all but the smallest nanorings studied. This effect has been assigned to exciton–exciton annihilation and fit to a one-dimensional exciton diffusion model, which confirms that the exciton size and/or its mobility are inversely proportional to the nanoring size.
Original languageEnglish
Pages (from-to)18416–18425
Number of pages10
JournalThe Journal of Physical Chemistry C
Issue number34
Early online date30 Jul 2020
Publication statusPublished - 27 Aug 2020

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