Ultrafast Singlet Fission and Intersystem Crossing in Halogenated Tetraazaperopyrenes.

Autor:	Wollscheid N; Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany.; Centre for Advanced Materials, Universität Heidelberg, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany., Günther B; Anorganisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany., Rao VJ; Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany.; Centre for Advanced Materials, Universität Heidelberg, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany., Berger FJ; Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany.; Centre for Advanced Materials, Universität Heidelberg, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany., Lustres JLP; Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany.; Centre for Advanced Materials, Universität Heidelberg, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany., Motzkus M; Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany.; Centre for Advanced Materials, Universität Heidelberg, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany., Zaumseil J; Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany.; Centre for Advanced Materials, Universität Heidelberg, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany., Gade LH; Anorganisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany., Höfener S; Institute of Physical Chemistry, Karlsruhe Institute of Technology (KIT), P.O. Box 6980, D-76131 Karlsruhe, Germany., Buckup T; Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany.; Centre for Advanced Materials, Universität Heidelberg, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany.
Jazyk:	angličtina
Zdroj:	The journal of physical chemistry. A [J Phys Chem A] 2020 Oct 01; Vol. 124 (39), pp. 7857-7868. Date of Electronic Publication: 2020 Sep 22.
DOI:	10.1021/acs.jpca.0c04852
Abstrakt:	Charge carrier multiplication via singlet fission into two triplet states has the potential to increase efficiencies of photovoltaics by one-third due to the reduction of thermalization losses. In the present work, we investigate tetraazaperopyrenes, a class of N -heteropolycyles, as suitable singlet fission candidates. Using a combined experimental and theoretical approach, fundamentally different mechanisms for triplet formation in solution and thin film are identified. In solution, an ultrafast intersystem crossing process is observed, which is accelerated for heavier halide substituents not only due to enhanced spin-orbit coupling but also due to the energy tuning between the S 1 and T 2 states. In thin films, a correlated triplet pair is formed coherently upon photoexcitation. Subsequently, an excimer formation is observed, which competes with the electronic decorrelation of the triplet pair. The comparison with peropyrene shows that aza-substitutions within the aromatic core can be a powerful strategy for tuning the energy levels of the states important to singlet fission.
Databáze:	MEDLINE
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