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Annihilation dynamics of molecular excitons measured at a single perturbative excitation energy
journal contributionposted on 04.09.2020 by Constantin Heshmatpour, Pavel Malevich, Felix Plasser, Maximilian Menger, Christoph Lambert, Frantisek Sanda, Jürgen Hauer
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Exciton–exciton annihilation (EEA) is a ubiquitous phenomenon, which may limit the efficiency of photovoltaic devices. Conventional methods of determining EEA time scales rely on measuring the intensity dependence of third-order signals. In this work, we directly extract the annihilation rate of molecular excitons in a covalently joined molecular trimer without the need to perform and analyze intensity dependent data by employing fifth-order coherent optical spectroscopy signals emitted into ±2k⃗1 ∓ 2k⃗2 + k⃗3 phase matching directions. Measured two-dimensional line shapes and their time traces are analyzed in the framework of the many-body version of the Frenkel exciton model, extended to incorporate annihilation dynamics. Combining double-sided Feynman diagrams with explicit simulations of the fifth-order response, we identify a single peak as a direct reporter of EEA. We retrieve an annihilation time of 30 fs for the investigated squaraine trimer.
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Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through TUM International Graduate School of Science and Engineering (IGSSE), GSC 81.
DFG under Germany’s Excellence Strategy (EXC 2089/1-390776260).
Czech Science Foundation (Grant No. 17-22160S).
“Exciton-exciton annihilation probed by nonlinear spectroscopy” (MSMT Grant No. 8J19DE009, DAAD-Projekt 57444962).
Alexander von Humboldt Foundation.
Federal Ministry for Education and Research.