Regensburg 2010 – scientific programme

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O: Fachverband Oberflächenphysik

O 29: [CPP] Organic Electronics and Photovoltaics I (Joint Session DS/CPP/HL/O)

O 29.1: Talk

Tuesday, March 23, 2010, 09:30–09:45, H37

Side chain variations on dicyanovinyl-oligothiophenes studied by photoinduced absorption spectroscopy: consequences for small molecule organic solar cells — •Hannah Ziehlke¹, Roland Fitzner², Christian Koerner¹, Egon Reinold², Peter Baeuerle², Karl Leo¹, and Moritz Riede¹ — ¹Institut für Angewandte Photophysik, Technische Universität Dresden — ²Institut für Organische Chemie II und Neue Materialien, Universität Ulm

Oligothiophenes capped with electron-withdrawing dicyanovinyl groups (DCVnT) are promising candidates for applications in small molecule organic solar cells. These oligothiophene derivatives can act as electron donor in blend layers with C₆₀. Single heterojunction devices reach efficiencies above 4 %. The introduction of side chains as intermolecular spacer has little effect on the energetics and mainly influences the morphology of the evaporated thin film. In addition, the distance between donor and acceptor molecules and thus the energy transfer and charge separation at the interface can be controlled. The energetic and dynamic properties of the long lived photoexcitations in pristine and blend layers can be obtained by photoinduced absorption spectroscopy (PIA). We here characterize of DCV3T with zero, two, and four alkyl chains (Methyl and Butyl) via PIA spectroscopy complemented with morphological studies. Our results indicate that the energy transfer process at the heterojunction is more efficient for smaller spatial distances between donor and acceptor molecules.