Dresden 2017 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 32: Organic Thin Films I (joint session CPP/DS/HL, organized by DS)
CPP 32.8: Talk
Wednesday, March 22, 2017, 11:30–11:45, CHE 91
Correlation of Structure, Morphology, and Spectroscopic Properties of Polymorphic, Textured Squaraine Thin Films — •Frank Balzer1, Heiko Kollmann2, Martin Silies2, Matthias Schulz3, Arne Lützen3, Christoph Lienau2, and Manuela Schiek2 — 1University of Southern Denmark, Sønderborg, Denmark — 2University of Oldenburg, Germany — 3University of Bonn, Germany
The dihydroxy anilino squaraine 2,4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl]squaraine (SQIB) crystallizes into at least two polymorphic structures: a monoclinic and an orthorhombic phase. Spin-coated thin films are, depending on the annealing temperature, highly textured with two distinct morphological features, which are assigned to the two polymorphic forms. These features exhibit different absorption spectra with characteristic spectral signatures of molecular excitons with oblique transition dipole alignment and large Davydov splitting. The monoclinic form shows a blue-shifted absorption compared to the monomer band, while the absorption profile of the orthorhombic form is red-shifted. The transitions of the excitonic states for each polymorph are polarized mutually perpendicular, probed by polarization-resolved confocal spectro-microscopy. X-ray diffraction reveals a strong out-of-plane orientation. Crystalline domains are distributed with random in-plane orientation on the samples. Their local in-plane orientation is deduced from spectro-microscopy recordings as well as from polarized light microscopy.