Dresden 2011 – scientific programme

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DS: Fachverband Dünne Schichten

DS 14: Organic Electronics and Photovoltaics HL-I (jointly with CPP, HL, and O)

DS 14.2: Talk

Monday, March 14, 2011, 18:00–18:15, FOE Anorg

Influence of temperature and illumination on the photo-voltage of organic solar cells — •Johannes Widmer, Wolfgang Tress, Karl Leo, and Moritz Riede — Institut für Angewandte Photophysik, TU Dresden, George-Bähr-Straße 1, 01069 Dresden

Temperature plays an essential role in many processes in organic devices, including the current and voltage generation in organic solar cells. In this contribution, we focus on the open-circuit voltage of organic solar cells when varying illumination intensity and temperature in the range of 200K to 400K. Zinc phthalocyanine (ZnPc) and C60 are used as reference system and other materials are investigated in comparison to demonstrate the connection between the effective energy gap and the open-circuit voltage of a photovoltaic device. The use of doped transport layers in a p-i-n diode geometry allows to minimize the energetic losses between the active layers and the contacts and gives access to the quasi Fermi levels in the heterojunction. We can verify the dependence between the effective gap of a heterojunction and the open-circuit voltage. A substantial difference, however, is observed comparing the interplay of temperature and illumination intensity of bulk and flat heterojunction devices. Classic photo-diode like behaviour is observed for the open-circuit voltage of bulk heterojunction devices, as described by generation-recombination dynamics. In the case of a flat heterojunction, however, the influence of temperature and illumination become independent, which is not covered by the established theory. These findings can contribute to the understanding of the photo-voltage of organic devices.