Ultrafast Exciton Self-Trapping upon Geometry Deformation in Perylene-Based Molecular Aggregates

Alexander Schubert (1) , Volker Settels , Wenlan Liu , Frank Würthner , Christoph Meier (2, 3) , Reinhold F. Fink , Stefan Schindlbeck , Stefan Lochbrunner , Bernd Engels , Volker Engel (1)

1 Institut für Physikalische und Theoretische Chemie
2 Théorie (LCAR)
3 LCAR - Laboratoire Collisions Agrégats Réactivité

Femtosecond time-resolved experiments demonstrate that the photoexcited state of perylene tetracarboxylic acid bisimide (PBI) aggregates in solution decays nonradiatively on a time-scale of 215 fs. High-level electronic structure calculations on dimers point toward the importance of an excited state intermolecular geometry distortion along a reaction coordinate that induces energy shifts and couplings between various electronic states. Time-dependent wave packet calculations incorporating a simple dissipation mechanism indicate that the fast energy quenching results from a doorway state with a charge-transfer character that is only transiently populated. The identified relaxation mechanism corresponds to a possible exciton trap in molecular materials.

Mots clés: ab initio calculations; quantum dynamics; femtochemistry; excitation energy transfer (EET); photophysics

Domaines: Physique [physics]

Alexander Schubert, Volker Settels, Wenlan Liu, Frank Würthner, Christoph Meier, et al.. Ultrafast Exciton Self-Trapping upon Geometry Deformation in Perylene-Based Molecular Aggregates. Journal of Physical Chemistry Letters, 2013, 4 (5), pp.792-796. ⟨10.1021/jz4000752⟩. ⟨hal-00929907⟩