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Journal Article

Nuclear dynamics of singlet exciton fission in pentacene single crystals

MPS-Authors
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Rossi,  M.
Fritz-Haber-Institut der Max-Planck-Gesellschaft;
Simulations from Ab Initio Approaches, Theory Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;

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Schwoerer,  H.
Ultrafast Beam Applications, Scientific Service Units, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;

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Fulltext (public)

eabg0869.full.pdf
(Publisher version), 2MB

Supplementary Material (public)

suppl.zip
(Supplementary material), 73MB

Citation

Seiler, H., Krynski, M., Zahn, D., Hammer, S., Windsor, Y. W., Vasileiadis, T., et al. (2021). Nuclear dynamics of singlet exciton fission in pentacene single crystals. Science Advances, 7(26): eabg0869. doi:10.1126/sciadv.abg0869.


Cite as: http://hdl.handle.net/21.11116/0000-0007-751A-9
Abstract
Singlet exciton fission (SEF) is a key process for developing efficient optoelectronic devices. An aspect rarely probed directly, yet with tremendous impact on SEF properties, is the nuclear structure and dynamics involved in this process. Here, we directly observe the nuclear dynamics accompanying the SEF process in single crystal pentacene using femtosecond electron diffraction. The data reveal coherent atomic motions at 1 THz, incoherent motions, and an anisotropic lattice distortion representing the polaronic character of the triplet excitons. Combining molecular dynamics simulations, time-dependent density-functional theory, and experimental structure factor analysis, the coherent motions are identified as collective sliding motions of the pentacene molecules along their long axis. Such motions modify the excitonic coupling between adjacent molecules. Our findings reveal that long-range motions play a decisive part in the electronic decoupling of the electronically correlated triplet pairs and shed light on why SEF occurs on ultrafast time scales.