Dresden 2011 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 62: Organic Thin Films I
DS 62.6: Vortrag
Freitag, 18. März 2011, 11:30–11:45, GER 38
Electronic structure of diindenoperylene-fullerene heterojunctions — •Andreas Wilke1, Julia Wagner2, Mark Gruber2, Johannes Frisch1, Patrick Amsalem1, Antje Vollmer3, Benjamin Bröker1, Andreas Opitz2, Wolfgang Brütting2, and Norbert Koch1 — 1Humboldt-Universität zu Berlin, Brook-Taylor-Str. 6, 12489 Berlin — 2Universität Augsburg, Universitätsstr. 1, 86135 Augsburg — 3Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15,12489 Berlin
In organic photovoltaic cells (OPVCs) typically two organic materials with electron- acceptor and donor character are sandwiched between anode and cathode, forming either layered planar (PHJ) or bulk heterojunctions (BHJ), where charge separation occurs. We report on ultraviolet photoelectron spectroscopy (UPS) measurements on PHJ and BHJ of the donor diindenoperylene (DIP) and the acceptor C60. The results on energy level alignment at these heterojunctions are then discussed in comparison to the energy conversion efficiency achieved in corresponding OPVCs, which peaked at 4.1%. The offset between the highest occupied molecular orbital of DIP and the lowest unoccupied molecular orbital of C60, an estimate for the maximum achievable open circuit voltage, is 1.3 eV and 1.35 eV for the PHJ and BHJ, respectively. For comparison, OPVCs exhibited open circuit voltages up to 0.93 V. Our results demonstrate close agreement between the donor/acceptor energy level alignment and the open circuit voltage in devices and that induced carriers at contacts are beneficial for the energy conversion efficiency of OPVCs.