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Using Two-Dimensional Spectroscopy to Probe Relaxation, Decoherence, and Localization of Photoexcited States in pi-Conjugated Polymers

Abstract

We use the coarse-grained Frenkel-Holstein model to simulate the relaxation, decoherence, and localization of photoexcited states in conformationally disordered π-conjugated polymers. The dynamics are computed via wave-packet propagation using matrix product states and the time evolution block decimation method. The ultrafast (i.e., t < 10 fs) coupling of an exciton to C-C bond vibrations creates an exciton-polaron. The relatively short (ca. 10 monomers) exciton-phonon correlation length causes ultrafast exciton-site decoherence, which is observable on conformationally disordered chains as fluorescence depolarization. Dissipative coupling to the environment (modelled via quantum jumps) causes the localization of quasi-extended exciton states (QEESs) onto local exciton ground states (LEGSs, i.e., chromophores). This is observable as lifetime broadening of the 0-0 transition of the QEES in two-dimensional electronic coherence spectroscopy. However, as this process is incoherent, neither population increases of the LEGSs nor coherences with LEGSs are observable. Damping does cause lifetime broadening of vibronic satellites.

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Publication details

The article was received on 30 Apr 2019, accepted on 07 Jun 2019 and first published on 07 Jun 2019


Article type: Paper
DOI: 10.1039/C9FD00054B
Faraday Discuss., 2019, Accepted Manuscript

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    Using Two-Dimensional Spectroscopy to Probe Relaxation, Decoherence, and Localization of Photoexcited States in pi-Conjugated Polymers

    W. Barford, J. L. A. Gardner and J. Mannouch, Faraday Discuss., 2019, Accepted Manuscript , DOI: 10.1039/C9FD00054B

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