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O: Fachverband Oberflächenphysik
O 17: [DS] Organic Electronics and Photovoltaics II (Joint Session DS/CPP/HL/O)
O 17.5: Vortrag
Montag, 22. März 2010, 15:00–15:15, H8
Electronic properties of Cu-phthalocyanine-fullerene planar and bulk heterojunctions on PEDOT:PSS — •Andreas Wilke, Toshiko Mizokuro, Ralf Peter Blum, Jürgen P Rabe, and Norbert Koch — Institut für Physik, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 6, D-12489 Berlin
In organic photovoltaic cells (OPVCs) typically two organic materials with electron-acceptor and electron-donor properties are placed between anode and cathode, forming either a layered planar or mixed bulk heterojunction where charge separation should occur. To improve the efficiency of this central process it is important to know and understand the energy levels at such heterojunctions, and how they may depend on heterojunction morphology. We report ultraviolet and X-ray photoelectron spectroscopy studies on layered planar and mixed bulk heterojunctions of Cu-phthalocyanine (CuPc) and C60, a prototypical material pair for OPVCs. The respective heterojunctions were formed on poly(ethylene-dioxythiophene):poly(styrenesulfonate) substrates, in order to achieve morphologies comparable to those in actual OPVCs. The energy offset between the highest occupied levels of CuPc and C60 was determined to 1.3 eV for both the layered and mixed bulk heterojunction. Our results demonstrate that the energy levels that determined the efficiency of charge separation in OPVCs made of CuPC and C60 are independent of particular interface morphology, and that differences in device efficiency are due to other effects.
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