Dresden 2011 – scientific programme
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DS: Fachverband Dünne Schichten
DS 24: Organic Electronics and Photovoltaics CPP-II (jointly with CPP, HL, and O)
DS 24.8: Talk
Tuesday, March 15, 2011, 12:30–12:45, ZEU 222
Triplet Excitons and Cations in dicyanovinyl end-capped quaterthiophenes with varying side chain length — •Christian Koerner1, Hannah Ziehlke1, Roland Fitzner2, Egon Reinold2, Peter Bäuerle2, Karl Leo1, and Moritz Riede1 — 1Institut für Angewandte Photophysik, Technische Universität Dresden — 2Institut für Organische Chemie II und Neue Materialien, Universität Ulm
Dicyanovinyl end-capped oligothiophenes (DCV-nT) are highly suitable for systematical investigations of energy and charge transfer processes in donor-acceptor blends because of the tunability of electronic and morphological properties by varying e.g. length of backbone or side chains. Moreover, it has been shown to work well as absorber in small molecule organic solar cells (OSC) achieving up to 5.2% power conversion efficiency (PCE) for DCV-5T in a bulk heterojunction (BHJ) device1.
We use photoinduced absorption spectroscopy (PIA) to probe the long-living (µs-ms) excited states (triplet excitons, cations) after photoexcitation of DCV-nT:C60 blends. With PIA, their generation and recombination behaviour can be investigated. Here, we report our results obtained on a series of DCV-4Ts with varying side chains from none to methyl side chains which supposedly mainly influences the morphology of the thin film. We complement our studies by exploring the potential of these materials as absorber layer in planar and BHJ solar cells. For example, DCV-4T without side chains gives an open circuit voltage of 1V and PCEs of 1.9% in a BHJ solar cell with C60.
1 Fitzner et al., Adv. Func. Mat., accepted