Excitation energy transfer within covalent tetrahedral perylenediimide tetramers and their intermolecular aggregates

Charusheela Ramanan, Chul Hoon Kim, Tobin J. Marks, Michael R. Wasielewski

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)

Abstract

Perylenediimides (PDIs) offer a number of attractive characteristics as alternatives to fullerenes in organic photovoltaics (OPVs), including favorable orbital energetics, high extinction coefficients in the visible spectral region, photostability, and the capacity to self-assemble into ordered nanostructures. However, energy transfer followed by charge separation in PDI assemblies must kinetically out-compete excimer formation that limits OPV performance. We report on the excitation energy transfer (EET) rate in a covalently linked PDI tetramer in which the PDI chromophores are arranged in a tetrahedral geometry about a tetraphenyladamantane core. Transient absorption spectroscopy of the tetramer in CH2Cl2 reveals a laser intensity-dependent fast absorption decay component indicative of singlet-singlet annihilation resulting from intramolecular EET. Femtosecond fluorescence anisotropy measurements show that the EET time constant τ = 6 ps, which is similar to that predicted for a through-space Förster EET mechanism. Concentration-dependent steady-state spectroscopic studies reveal the formation of intermolecular aggregates of the tetramers in toluene. The aggregates are formed by cofacial π-stacking interactions between PDIs of neighboring tetramers. Transient absorption spectra of the aggregated tetramers in toluene solution demonstrate long-lived excited-state decay dynamics (τ ∼ 30 ns) in agreement with previous observations of PDI excimers.

Original languageEnglish
Pages (from-to)16941-16950
Number of pages10
JournalJournal of Physical Chemistry C
Volume118
Issue number30
DOIs
Publication statusPublished - Jul 31 2014

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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