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Weiche Materie Poster: Do., 13:00–15:30 D-P338
Structure and crystallinity study in thin films of poly(3-hexylthiophene)
Siddharth Joshi 1 , Souren Grigorian 1 , Ullrich Pietsch 1 , Achmad Zen 2 , Dieter
Neher 2
1 Festkörperphysik, Universität Siegen, Siegen, Germany – 2 Institut für Physik, Uni-
versität Potsdam, Potsdam, Germany
Organic material devices have gained a lot of attention from last decade due to their
application to polymeric electronic devices such as light-emitting diodes, Field-effect
transistor(FETs), and photovoltaic cells (PVs). The special interest are focus on the
low-cost devices based on polymeric materials prepared by simple solution processing.
Regioregular poly(3-hexylthiophene) (P3HT) is one of the most promising polymer
material for such purpose having high charge carrier mobility. Up-to now one of the
fundamental problems in polymer transistors are to understand the relation between
the surface morphology and the charge transport as they have relatively low chargecarrier
mobility compared to inorganic semiconductor devices.
Therefore our studies are focussed on the investigation of the structural order [1]
and the degree of crystallinity of semicrystalline thin films (few nm) of low and high
molecular weight of P3HTs using X-ray scattering techniques. For detailed studies
grazing incidence X-ray diffraction [2,3] (GID) has employed to determine the vertical
and lateral structures of films, additionally, X-ray reflectivity technique has been used
to know the average thickness of such organic thin films using synchrotron radiation
source. The degree of crystallinity was determined utilising Rulands method [4]. The
present status of our calculations suggests that P3HT thin films having low molecular
weight show a high degree of crystallinity compared to films with high molecular
weight. This has been explained by the fact that crystalline parts of P3HT are embedded
into the amorphous matrix. Temperature and concentration dependent study
of the interplaner distances d of the P3HT thin films have shown that the d spacing
increases with temperature and depending on layer thickness. In general, structural investigations
at thin polymer films suffer from possible beam damage caused by probing
high-intense synchrotron radiation. Therefore the content of structural investigations
received from experiment might depend on the synchrotron radiation source for the
experiment.
[1] R. J. Kline, et. al., Nature materials, 5 (2006) 222.
[2] A. Zen, et al., Macromolecules, 39 (2006) 2162.
[3] A. Zen., et al., Adv. Funct. Mater. 14 (2004) 757.
[4] W. Ruland, Acta Cryst., 14 (1961) 1180.