Dresden 2014 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 3: Organic Electronics and Photovoltaics I (DS jointly with HL, O)

O 3.8: Vortrag

Montag, 31. März 2014, 11:45–12:00, ZEU 222

Temperature-dependent molecular orientation of the organic semiconductor PTCDI-C₈: Optical and structural properties — •Sebastian Bommel^1,2, Linus Pithan², Christopher Weber², Anton Zykov², Gonzalo Santoro¹, Stephan V. Roth¹, Jörg Megow², and Stefan Kowarik² — ¹Deutsches Elektronen-Synchrotron (DESY), Notkestr. 85, D-22607 Hamburg, Germany — ²Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, D-12489 Berlin, Germany

Optical and structural properties of molecular materials are not only essential for the rational design of opto-electrical devices, but also for the understanding of intermolecular interactions. Here, we report on the structural and optical properties of the organic semiconductor PTCDI-C₈ investigated by temperature-dependent Grazing Incidence X-ray Diffraction (GIXD) and photoluminescence (PL) measurements. Our in situ studies yield a large impact of temperature on unit cell parameters and optical transitions. The energy of the optical transition E₁₀-E₀₁ in the PL spectra shifts from 1.80 eV for 273 K to 1.85 eV for 413 K. Furthermore, a rearrangement of the molecular ensemble was found, indicated by a large change of the beta-angle of the PTCDI-C8 unit cell from 107^∘ (273 K) to 102^∘ (413 K). The influence of these structural changes, which are an indication for a change of molecular orientation with temperature, on the optical properties will be discussed in detail. Additionally, the structural and optical properties are supported by temperature-dependent molecular dynamics (MD) simulation based calculations.