Dresden 2011 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 12: Organic Semiconductors II: Solar Cells B (jointly with HL, DS)
CPP 12.9: Vortrag
Dienstag, 15. März 2011, 12:45–13:00, ZEU 222
Surface structure of organic heterojunction solar cells — •M. Zerson1, E.-C. Spitzner1, C. Riesch1, A. Sperlich2, H. Kraus2, A. Förtig2, C. Deibel2, V. Dyakonov2, R. Lohwasser3, M. Thelakkat3, and R. Magerle1 — 1Chemische Physik, TU Chemnitz — 2Experimental Physics VI, Julius-Maximilians-University of Würzburg — 3Makromolekulare Chemie I, Univ. Bayreuth
In organic heterojunction solar cells based on P3HT and PCBM, the charge transfer within the active layer as well as the charge transport towards the electrodes are determined by the electronic properties of the interfaces and their microstructure. The surface of semicrystalline polypropylene has been shown to be covered by a thin layer of amorphous material. We aim at investigating potential similarities between organic semiconductors for photovoltaics. We report on 3D depth profiling of the surface structure of different types of P3HT and blends of P3HT with PCBM using amplitude modulation atomic force microscopy. From a map of amplitude-phase-distance curves, the tip indentation into the soft (compliant) amorphous surface layer is measured. This spatial information serves as depth coordinate for reconstructing high resolution cross sections and 3D depth profiles of the top 10 nm of the specimen. Furthermore, the shape of the unperturbed (true) surface and the thickness of the amorphous top layer are determined. The latter is found to be between 4 and 10 nm thick, depending on the type of material and the sample preparation conditions (thermal and solvent annealing). We discuss the impact of the thickness of the amorphous top layer on the efficiency of organic solar cells.