Unified picture of the photoexcitations in phenylene-based conjugated polymers: Universal spectral and dynamical features in subpicosecond transient absorption

B. Kraabel, Victor I Klimov, R. Kohlman, S. Xu, H. L. Wang, D. W. McBranch

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Abstract

Using subpicosecond transient absorption spectroscopy, we investigate the primary photoexcitations in thin films and solutions of several phenylene-based conjugated polymers and an oligomer. We identify several features in the transient absorption spectra and dynamics that are common to all of the materials which we studied from this family. The first spectral feature is a photoinduced absorption (PA) band peaking near 1 eV that has intensity-dependent dynamics that match the stimulated emission dynamics exactly over two orders of magnitude in excitation density. This band is associated with singlet intrachain excitons. The second spectral feature (observed only in thin films and aggregated solutions) is a PA band peaking near 1.8 eV, that is longer lived than the 1 eV exciton PA band, and that has dynamics that are independent (or weakly dependent) on excitation density. This feature is attributed to polarons, generated through a mechanism that is sample dependent. In pristine samples, polarons are generated via a mechanism that is quadratic in exciton density, whereas in photodegraded samples or samples doped with electron acceptors, the generation mechanism becomes linear in exciton density.

Original languageEnglish
Pages (from-to)8501-8515
Number of pages15
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume61
Issue number12
Publication statusPublished - 2000

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Photoexcitation
Conjugated polymers
photoexcitation
Excitons
Absorption spectra
excitons
absorption spectra
Polarons
polymers
polarons
Thin films
Stimulated emission
thin films
stimulated emission
Absorption spectroscopy
oligomers
Oligomers
excitation
absorption spectroscopy
LDS 751

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

Unified picture of the photoexcitations in phenylene-based conjugated polymers : Universal spectral and dynamical features in subpicosecond transient absorption. / Kraabel, B.; Klimov, Victor I; Kohlman, R.; Xu, S.; Wang, H. L.; McBranch, D. W.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 61, No. 12, 2000, p. 8501-8515.

Research output: Contribution to journalArticle

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AU - Wang, H. L.

AU - McBranch, D. W.

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