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DS: Fachverband Dünne Schichten
DS 17: [CPP] Organic Electronics and Photovoltaics II (Joint Session DS/CPP/HL/O)
DS 17.5: Talk
Tuesday, March 23, 2010, 14:45–15:00, H37
Study of Sub-Bandgap States in Polymer-Fullerene Solar Cells — •Martin Presselt1, Felix Herrmann1, Marco Seeland1, Maik Bärenklau1, Sebastian Engmann1, Roland Rösch1, Wichard J. D. Beenken2, Sviatoslav Shokhovets1, Harald Hoppe1, and Gerhard Gobsch1 — 1Experimental Physics I, Institute of Physics & Institute of Micro- und Nanotechnologies, Ilmenau University of Technology, Weimarer Str. 32, 98693 Ilmenau, Germany — 2Theoretical Physics I, Institute of Physics, Ilmenau University of Technology, Weimarer Str. 25, 98693 Ilmenau, Germany
At present polymer-fullerene blends are widely used to build organic solar cells. The main contribution to their photocurrent originates from optical transitions between occupied states below the HOMO level and unoccupied states above the LUMO level of the polymer.
In this work, we investigated the origin of states contributing to the optical absorption in the sub-bandgap spectral range and the resulting photocurrent in P3HT-PCBM bulk heterojunction solar cells. Photothermal deflection spectroscopy, temperature dependent external quantum efficiency, photoluminescence and electroluminescence as well as spectroscopic ellipsometry measurements have been carried out. Effects due to different P3HT-PCBM blending ratios and annealing temperatures have been studied.
Two models are discussed to explain the experimental observations: optical transitions involving (a) disorder and/or defect related states, and (b) charge transfer complexes.