Berlin 2015 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 36: Organic Electronics and Photovoltaics: Transport of Charges – from Molecules to Devices (jointly with CPP, HL)
TT 36.8: Talk
Tuesday, March 17, 2015, 11:30–11:45, C 130
The molecular structure of a high electron mobility n-type copolymer [P(NDI2OD-T2)] as studied by Infrared Transition Moment Orientational Analysis [IR-TMOA] — •Arthur Markus Anton1, Robert Steyrleuthner2, Wilhelm Kossack1, Dieter Neher3, and Friedrich Kremer1 — 1Institut für Experimentelle Physik I, Universität Leipzig, Germany — 2Fachberich Physik, Freie Universität Berlin, Germany — 3Institut für Physik und Astronomie, Universität Potsdam, Germany
To investigate the molecular order in thin layers of P(NDI2OD-T2) a novel technique, named Infrared Transition Moment Orientational Analysis (IR-TMOA), is employed. Structure-specific vibrational bands are analyzed in dependence on polarization and inclination of the sample film with respect to the optical axis. Making use of IR specificity we deduce the molecular order parameter tensor for the respective moieties with regard to the sample coordinate system and determine separately the orientation of atomistic planes defined through the naphthalenediimide (NDI) and bithiophene (T2) units relative to the substrate, and hence, relative to each other. We observe that chlorobenzene causes the T2 planes to align preferentially parallel to the substrate at an angle of 29∘. A chloronaphthalene:xylene mixture, instead, gives rise to a reorientation of the T2 units from a face on into an edge on arrangement (65 to 70∘). In contrast, the NDI part remains basically unaffected. For both solvents, evidence for aggregated chains is observed by UV/vis absorption spectroscopy [Steyrleuthner et al., J. Am. Chem. Soc. 136 (2014)].