Regensburg 2002 – wissenschaftliches Programm
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SYOH: Organische Halbleiter
SYOH 7: Poster
SYOH 7.52: Poster
Montag, 11. März 2002, 18:00–21:00, C
W-band and X-band ESR study of photoinduced charge transfer in conjugated polymer-fullerene composites — •M. Pientka1, J. De Ceuster2, E. Goovaerts2, J.C. Hummelen3, J. Parisi1, and V. Dyakonov1 — 1University of Oldenburg, Faculty of Physics, Department of Energy and Semiconductor Research, D-26111 Oldenburg, Germany — 2University of Antwerp, Physics Department, Universteitsplein 1, B-2610 Antwerpen, Belgium — 3Stratingh Institute and MSC, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
Light-Induced-Electron-Spin Resonance (LESR) is a sensitive technique to probe the charge transfer in organic donor-acceptor systems. In composites of poly(2-methoxy -5-(3-,7-dimethyloctyloxy)-1,4-phenylenevinylene)(MDMO-PPV) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), two paramagnetic species are formed under illumination. One peak is assigned to the polaron P+ on the PPV backbone, the other one to the radical anion of the fullerene molecule. In a first experiment, the temperature and microwave power dependence of the signal is studied. It is found a different saturation behaviour of the two radicals due to different spin lattice relaxation times. Additionally by studying the light intensity dependence of the signal, we find a square root behaviour which is characteristic for a bimolecular decay. The g-anisotropy of both radicals are resolved in high frequency (95 GHz) LESR. The polaron cation on the polymer possesses axial symmetry (g∥=2.0034(1), g⊥=2.0024(1)), the polaron anion on the fullerene has a rhombic symmetry with gx=2.0003(1), gy=2.0001(1), gz=1.9982(1).