Dresden 2006 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 23: POSTER Functional Organic Thin Films
CPP 23.52: Poster
Donnerstag, 30. März 2006, 17:00–19:00, P2
Efficient heterojunction organic solar cells with high photovoltages based on a new low-band-gap oligothiophene — •Kerstin Schulze1, Christian Uhrich1, Karl Leo1, Martin Pfeiffer1, Eduard Brier2, and Peter Bäuerle2 — 1Institut für Angewandte Photophysik, Technische Universität Dresden, George-Bähr-Str. 1, 01069 Dresden — 2Abteilung Organische Chemie II, Universität Ulm, Albert Einstein Allee 11, 89081 Ulm
We report on efficient vacuum deposited heterojunction organic solar cells containing a new oligothiophene derivative with absorption onset at around 700nm as a donor and fullerene C60 as an acceptor. At the heterointerface between the low-band-gap oligothiophene and C60, photogenerated excitons from both materials are efficiently separated into electrons on C60 and holes on the low lying HOMO of the oligothiophene. With these materials we can reach high open circuit photovoltages of up to 1.0V. The most efficient solar cells (3.1% power efficiency at 133mW/cm^2 simulated sunlight) are obtained when the photoactive heterojunction is embedded between a p-doped hole transport layer on the anode side and a thin exciton blocking layer and aluminium on the cathode side. However, due to the high ionization energy of the oligothiophene (around 5.6+/-0.1eV as determined from UPS), hole injection from any anode or hole transport layer is difficult and the IV-curves thus show a characteristic s-shape which reduces the fill factor FF. It is found that the actual FF sensitively depends on the workfunction of the p-doped hole transport layer and the thickness of the oligothiophene layer.