Annihilation dynamics of molecular excitons measured at a single perturbative excitation energy
journal contributionposted on 04.09.2020, 10:44 by Constantin Heshmatpour, Pavel Malevich, Felix PlasserFelix Plasser, Maximilian Menger, Christoph Lambert, Frantisek Sanda, Jürgen Hauer
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.
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.