Ultrafast coherent exciton dynamics in size-controlled perylene bisimide aggregates

Seongsoo Kang, Christina Kaufmann, Yongseok Hong, Woojae Kim, Agnieszka Nowak-Król, Frank Würthner, Dongho Kim

Research output: Contribution to journalArticle

Abstract

For H-aggregates of perylene bisimide (PBI), it has been reported that upon photoexcitation, an initially delocalized Frenkel exciton is localized by excimer formation. However, in recent studies, the beforehand exciton dynamics preceding the excimer formation was suggested in larger aggregates consisting of at least more than 10-PBI subunits, which was not observed in small aggregates comprising less than four-PBI subunits. This feature implies that the size of molecular aggregates plays a crucial role in the initial exciton dynamics. In this regard, we have tried to unveil the initial exciton dynamics in PBI H-aggregates by tracking down the transient reorientations of electronic transition dipoles formed by interactions between the PBI subunits in systematically size-controlled PBI H-aggregates. The ultrafast coherent exciton dynamics depending on the molecular aggregate sizes can be distinguished using polarization-dependent femtosecond-transient absorption anisotropy spectroscopic measurements with a time resolution of ∼40 fs. The ultrafast decay profiles of the anisotropy values are unaffected by vibrational relaxation and rotational diffusion processes; hence, the coherent exciton dynamics of the PBI H-aggregates prior to the excimer formation can be directly revealed as the energy migration processes along the PBI H-aggregates.

Original languageEnglish
Article number064501
JournalStructural Dynamics
Volume6
Issue number6
DOIs
Publication statusPublished - 2019 Nov 1

    Fingerprint

All Science Journal Classification (ASJC) codes

  • Radiation
  • Instrumentation
  • Condensed Matter Physics
  • Spectroscopy

Cite this

Kang, S., Kaufmann, C., Hong, Y., Kim, W., Nowak-Król, A., Würthner, F., & Kim, D. (2019). Ultrafast coherent exciton dynamics in size-controlled perylene bisimide aggregates. Structural Dynamics, 6(6), [064501]. https://doi.org/10.1063/1.5124148