Dresden 2009 – scientific programme
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SYOP: Symposium Organic Photovoltaics: From Single Molecules to Devices
SYOP 4: Organic Photovoltaics: from Single Molecules to Devices
SYOP 4.41: Poster
Thursday, March 26, 2009, 16:30–19:00, P1A
Donor-Acceptor Block Copolymers for their Application in Organic Photovoltaics. — •Sven Hüttner1, 2, Michael Sommer2, Ullrich Steiner1, and Mukundan Thelakkat2 — 1Cavendish Laboratory, University of Cambridge, UK — 2Angewandte Funktionspolymere, Universität Bayreuth, Germany
Organic photovoltaic cells rely on two different materials, a donor (p-type) and an acceptor (n-type) material. In conventional approaches, both materials are blended together to form the active layer. We use a block copolymer instead, where a donor and an acceptor polymer are covalently linked. Block copolymers are well known to phase separate in highly ordered nanostructures on lengthscales of the exciton diffusion length. The acceptor block consists of perylene bisimide moieties and shows excellent electronic properties. Different donor blocks have been synthesized - one of the block copolymers features poly(3-hexylthiophene) (P3HT). We demonstrate photovoltaic devices based on these polymers with high external quantum efficiencies up to 30%.
The investigation of the morphology is accompanied by transient absorption spectroscopy resolving the exciton formation, separation and recombination processes on a time scale from ps to ms. Furthermore organic thin film transistors are used to characterize the transport properties in these materials displaying unique properties: Initially all materials exhibit p-type character after processing. However, depending on the post treatment and on the molecular weight ratios of blocks, we can switch the polarity of the transistor or achieve ambipolar transport.