Berlin 2018 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 25: Interfaces and Thin Films II
CPP 25.10: Talk
Tuesday, March 13, 2018, 12:30–12:45, PC 203
Real-Time Study on Growth and Packing Behavior of PDIs Thin Films Influenced by Side-Chains Modification — •Valentina Belova1, Benjamin Wagner1, Berthold Reisz1, Clemens Zeiser1, Giuliano Duva1, Jakub Rozbořil2, Jiří Novák2, Alexander Gerlach1, Alexander Hinderhofer1, and Frank Schreiber1 — 1Institut für Angewandte Physik, Tübingen, Germany — 2Masaryk University, Brno, Czech Republic
We study the growth of two highly performing small molecule organic semiconductors from the perylene diimide family (PDIs) interesting for photovoltaic application due to their good electron-accepting properties [1]: PDIR-CN2 and PDIF-CN2 whose chemical structures differ only in the imide substituents: branched alkyl chains and linear fluoroalkyl chains, respectively. Both types of substituents introduce some degree of steric hindrance for intermolecular interaction affecting solid state packing during vacuum deposition and thus induce specific structure-dependent optoelectronic properties in thin films. The phase transition from an amorphous structure to crystalline domains was followed in situ and in real-time by X-ray diffraction as a function of substrate temperature. We examined the relationship between structural properties and optical signatures probed via differential reflectance spectroscopy in real-time, ellipsometry and photoluminescence. A new crystalline polymorph for PDIR-CN2 at high temperatures was found. We observed that the fluorinated chains contribute to crystallization inhibition and surface roughening due to their high electron density. [1] V. Belova et al., JACS, 139, 8474 (2017).