Origin of line broadening in the electronic absorption spectra of conjugated polymers: Three-pulse-echo studies of MEH-PPV in toluene

Gregory D. Scholes, Delmar S. Larsen, Graham R. Fleming, Garry Rumbles

Research output: Contribution to journalArticle

78 Citations (Scopus)

Abstract

Integrated three-pulse stimulated echo peak shift data are compared for N, N-bis-dimethylphenyl-2,4,6,8-perylenetetracarbonyl diamide and (Formula presented) (MEH-PPV) in toluene solvent. These two molecules represent a model probe of solvation dynamics and a prototypical soluble, electroluminescent conjugated polymer, respectively. The results indicate that it is inappropriate to describe the linear absorption spectrum of MEH-PPV as being primarily inhomogeneously broadened. Conformational disorder along the polymer backbone gives rise to an ensemble of polyene electronic oscillators that are strongly coupled to each other. As a consequence, fluctuations in the electronic energy gap on a time-scale of 50-fs derive primarily from bath-mediated exciton scattering. The data reported here provide an explanation for the broad, structureless electronic absorption of MEH-PPV. This interpretation provides a valuable insight into the nature of the initial photoexcited state, and the efficient population of the emissive state.

Original languageEnglish
Pages (from-to)13670-13678
Number of pages9
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume61
Issue number20
DOIs
Publication statusPublished - Jan 1 2000

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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