Film morphology and photophysics of polyfluorene

A. J. Cadby, P. A. Lane, H. Mellor, S. J. Martin, M. Grell, C. Giebeler, D. D.C. Bradley, M. Wohlgenannt, C. An, Z. V. Vardeny

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Abstract

We have studied the interplay between photophysics and film morphology of poly(9,9-dioctyl)fluorene (PFO) using a variety of optical probes. Upon slowly warming a spin-cast PFO film from 80 to 300 K, a fraction of the sample is transformed into a different solid phase, the β phase. Absorption and electroabsorption measurements show that the β phase has more extended conjugation than the glassy phase. As a consequence, excited states of the β phase are redshifted and have higher polarizability. The photoinduced absorption spectrum of a glassy PFO film is dominated by triplet excitons, whereas both polarons and triplet excitons are seen in a sample containing a fraction of the β phase. The dependence of the photoinduced absorption and photocurrent upon the excitation wavelength shows that there is a clear link between polaron and triplet photogeneration.
Original languageEnglish (US)
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume62
Issue number23
DOIs
StatePublished - Dec 15 2000
Externally publishedYes

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