Dr. Souren Grigorian "Real-time Synchrotron Studies of Conjugated Organic Systems"
Institute of Physics, University of Siegen, Germany
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When |
May 14, 2014 from 02:15 PM to 03:00 PM |
Where | Seminarraum A, FMF, Stefan-Meier-Str. 21, Freiburg |
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Surface sensitive X-ray techniques have emerged to a versatile and frequently used method in the field of thin organic films and patterned nanostructures. Combination of x-ray reflectivity and grazing incidence x-ray diffraction (GIXD), especially, grazing incidence in- and out-of-plane geometries allow to probe the ordering and structural properties in the lateral directions as well as along to the normal of the thin film surface. GIXD technique has been widely used for the structural investigations of polythiophene films, in particular, extensively studied poly(3-hexylthiophene)s (P3HT) [1,2]. However, is not completely understood how an improvement in crystallinity is correlated to the enhancement of the thin film mobility. Despite the current efforts to unravel a relation between the microstructural properties and the device performance, typically the structural and electrical studies were addressed separately [1,3].
Recently combined in situ studies of the structural and electrical properties during solidification of polythiophene films were realized in the typical lateral OFET geometry [4]. Time dependent measurements allow monitor all stages of solution-gel-solid transitions and simultaneous detection of the electrical and the structural changes during the solidification process. The observed complex time-dependence of X-ray intensity and the current response reveal a highest conducting level for a transition phase before the final solidification. A difference of the solidification scenario between pure P3HT and mixed with fullerenes systems will also be addressed.
1. Y. Kim, S. Cook, S. M. Tuladhar, S. A. Choulis, J. Nelson, J. R. Durrant, D. D. C. Bradley, M. Giles, I. Mcculloch, C. S. Ha and M. Ree, Nature Materials, 2006, 5, 197
2. S. Grigorian, D. Tranchida, D. Ksenzov, D.; Schäfers, F.; Schönherr, H.; Pietsch, U. Eur. Pol. J., 2011, 47, 2189
3. R. J. Kline, M. D. Mcgehee and M. F. Toney, Nat Mater, 2006, 5, 222
4. L.Grodd, U. Pietsch, S. Grigorian. Macromol. Rapid Commun. 2012, 33,1765