Berlin 2005 – scientific programme
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SYOO: Organic Optoelectronics and Photonics
SYOO 6: Poster
SYOO 6.23: Poster
Monday, March 7, 2005, 18:00–20:00, Poster TU A
The influence of active layer morphology on the performance of organic vacuum deposited bulk heterojunction solar cells — •Stefan Sonntag1, Martin Bauer1, Martin Pfeiffer1, Karl Leo1, Peter Bäuerle2, and Paul Simon3 — 1Institut für Angewandte Photophysik, TU Dresden, Germany — 2Abteilung Organische Chemie II und Sektion Massenspektrometrie Universität Ulm — 3Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
The critical influence of the active layer morphology is known for polymeric bulk heterojunction solar cells. In particular, the performance can be strongly improved by reducing the typical scale of phase separation between the donor and the acceptor component. In solar cells based on a bulk heterojunction between zinc phthalocyanine (ZnPc) and fullerene C60, we find a significantly improved performance with fill factors up to 57 per cent when the active layer is deposited onto heated substrates (150∘C). The heating leads to some degree of phase separation including crystalline C60 domains that enhance electron delocalization and thus reduce recombination losses. Moreover, we studied the influence of substrate temperature during layer growth for bulk heterojunctions of thiophene oligomers and C60. Firstly, the absorption of the thiophene is enhanced and red shifted at higher substrate temperatures due to a co-planarization of the thiophene rings in the solid. And secondly, the fill factor is improved significantly due to reduced recombination losses at low electric fields. Finally, we will discuss the influence of the oligomer length on the properties of the bulk heterojunction and the potential of thiophene oligomers for solar cells.