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Title: Structure formation in perfluoropentacene:diindenoperylene blends and its impact on transient effects in the optical properties studied in real-time during growth

We discuss the result of the competing effects of favourable intermolecular interactions and steric incompatibilities due to the size mismatch of perfluoropentacene (PFP) and diindenoperylene (DIP) on the structure formation and associated optical properties in mixed films. Using real-time grazing incidence X-ray diffraction we investigate the size of coherently scattering islands l{sub s} as a function of film thickness and mixing ratio. We find that for PFP:DIP 1:2 blends l{sub s} is by a factor of ∼4 smaller than in pure DIP films, while l{sub s} of the PFP:DIP 2:1 blends is not significantly reduced compared with pure PFP. Yet, we observe an increase in l{sub s} with film thickness for all of the samples, independent on the mixing ratio. In parallel with the structural characterization we investigate the evolution of the absorption spectra in the visible spectral range and its dependence on l{sub s} in situ during film growth using differential reflectance spectroscopy. We observe a surprisingly strong effect of changes in the structural order on the shape of ε{sub 2,} {sub xy}(E), evident by a pronounced evolution of characteristic peaks in the thickness range from 1.6 nm to 9.6 nm. The combined results of the real-time experiments allowmore » to identify the thickness dependent crystal grain size as the origin of the observed transient effects in the absorption spectra.« less
Authors:
; ; ; ; ;  [1] ;  [1] ;  [2]
  1. Universität Tübingen, Institut für Angewandte Physik and LISA, Auf der Morgenstelle 10, 72076 Tübingen (Germany)
  2. (Japan)
Publication Date:
OSTI Identifier:
22251528
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 139; Journal Issue: 17; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION SPECTRA; CRYSTALS; FILMS; GRAIN SIZE; GRAZING; INTERACTIONS; OPTICAL PROPERTIES; SPECTROSCOPY; THICKNESS; X-RAY DIFFRACTION