Regensburg 2002 – wissenschaftliches Programm
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SYOH: Organische Halbleiter
SYOH 7: Poster
SYOH 7.53: Poster
Montag, 11. März 2002, 18:00–21:00, C
Photoinduced absorption spectroscopy on MDMO-PPV/PCBM composites — •M. Knipper1, M. Pientka1, S. Böger1, Z. Chiguvare1, I. Riedel1, J.C. Hummelen2, J. Parisi1, and V. Dyakonov1 — 1University of Oldenburg, Faculty of Physics, Department of Energy and Semiconductor Research, D-26111 Oldenburg, Germany — 2Stratingh Institute and MSC, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
Photoinduced absorption spectroscopy is a well known excited states
characterisation technique
of conjugated polymers. We have applied this method to investigate
organic donor-acceptor systems that are relevant for applications in
organic solar
cells. In pristine MDMO-PPV, we find a strong peek at 1.35 eV which is
assigned to the
first excited state of the exitonic triplet system. In PPV/PCBM
mixtures, the 1.35eV peak
vanishes and, instead two new peaks occur - one at 1.38eV and the other
one at 1.2eV. We
assign these peaks to the polaronic states which are created due to
electron transfer from the
polymer to the C60.
The signal intensity is studied depending on temperature, laser
excitation power
and chopping frequency of the laser light. With the detection of the
in-phase and
out-of-phase signal and their dependence of the chopping frequency, we
determine the
lifetime of the polaronic states in the range of milliseconds. The
excitation power dependence
of the signal allows us to discriminate between monomolecular and
bimolecular decay.