Photophysics of charge-transfer excitons in thin films of π -conjugated polymers

Zhendong Wang, Sumit Mazumdar, Alok Shukla

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Abstract

We develop a theory of the electronic structure and photophysics of interacting chains of π -conjugated polymers to understand the differences between solutions and films. While photoexcitation generates only the intrachain exciton in solutions, the optical exciton as well as weakly allowed charge-transfer excitons are generated in films. We extend existing theories of the lowest polaron pair and charge-transfer excitons to obtain descriptions of the excited states of these interchain species, and we show that a significant fraction of ultrafast photoinduced absorptions in films originates from the lowest charge-transfer exciton. Our proposed mechanism explains the simultaneous observation of polaronlike-induced absorption features peculiar to films in ultrafast spectroscopy and the absence of mobile charge carriers as deduced from other experiments. We also show that there is a 1:1 correspondence between the essential states that describe the photophysics of single chains and of interacting chains that constitute thin films.

Original languageEnglish (US)
Article number235109
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume78
Issue number23
DOIs
StatePublished - Dec 1 2008

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ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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