2D polarization resolved optical spectroscopy for exploration of conformation, energy transfer and aggregation of macromolecules (conjugated polymers and proteins) within different environments under the goal to contribute to the improvement of organic bulk heterojunction solar cells.
Electrical Energy Systems, Power Management, Power Electronics, Electrical Machines and Drives
Experimental and Theoretical Physics of Polymers
Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
Final Report Abstract
Understanding the aggregation of macromolecules is essential in many areas of research and applications. Optical investigation methods are superior to other techniques due to their noninvasiveness and facile application. A very promising tool for revealing structural information of the self-organization of macromolecules into larger structures is the two-dimensional polarization imaging (2D POLIM), which was recently developed by Ivan Scheblykin in Lund. Within this project, I applied 2D POLIM to investigate conjugated polymer films for organic photovoltaics provided by our collaborators in Linköping. Films of liquid crystalline poly[2,3-bis(3-octyloxy-phenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1) were fabricated by a floating film transfer method. I found these films to be well ordered containing mm-sized domains of homogeneously oriented TQ1 chains, which demonstrates the promising prospect of this method for upscaling it to large area fabrication of organic photovoltaics. Moreover, the structural information provided by local correlations of polarization parameters obtained by 2D POLIM enhances the understanding of the film formation process, which is needed for further improvement. I also studied BHJ mixtures of TQ1 (donor) and poly(N,N’-bis(2-octyldodecyl)naphthalene-1,4,5,8-bis(dicarbox-imide)-2,6-diyl-alt-2,2’-bithiophene-5,5’-diyl) (N2200, electron acceptor). By 2D POLIM I visualized the microstructure of these BHJ films, which revealed a correlation between experimental parameters and power conversion efficiencies of fabricated solar cells, enabling improvement of fabrication routines for such BHJ films. Recently, the group in Lund had joined the investigation of organometal-halide perovskites. This allowed me to study the photophysical properties of such nanocrystals. The understanding gained from this study is useful for the design of new materials for organic optoelectronics. Further, I continued the investigation of the aggregation of mono-stained proteins linked to Parkinson disease (PD) in brain tissue. The results provide new knowledge on pathologic pathways of PD. They further demonstrate the power of 2D POLIM to contribute to the understanding of pathological pathways in protein aggregation linked to neurodegenerative diseases. 2D POLIM is superior to already existing optical investigation methods, because it is easily applicable, it can be applied to mm-sized tissue areas, and it requires only one type of labels in contrast to similar powerful imaging methods which employ Förster resonance energy transfer between spectrally differing donor and acceptor labels. Finally, the project in Lund enabled me to find a co-author needed for publishing my previous work on fluorescence correlation spectroscopy using reflecting substrates (done within DFG-FOR 887). This publication, on the one hand, explains and demonstrates a sophisticated method, which can be used for retrieving information on structure and dynamics in thin soft matter films. On the other hand, the observed structure and dynamics in the studied liquid crystal films contribute to the understanding of the influence of long-range interface forces in this model liquid crystal.
Publications
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Exploring the Electronic Band Structure of Organometal Halide Perovskite via Photoluminescence Anisotropy of Individual Nanocrystals, Nano Letters, 16(8), 5087–5094, 2016.1
D. Täuber, A. Dobrovolsky, R. Camacho, I. Scheblykin
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Fluorescence correlation spectroscopy in thin films at reflecting substrates as a means to study nanoscale structure and dynamics at soft matter interfaces, Physical Review E, 94(1), 012804, 2016.2
D. Täuber, K. Radscheit, C. von Borczyskowski, V. Al. Osipov, and M. Schulz
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Two-dimensional polarization microscopy reveals polymer chain self-organization in thin films of conjugated polymers, in „Self-Assembly in the world of polymers, 80th Prague Meeting on Macromolecules,“ eds: P. Stepánek, J. Kotek, Institute of Macromolecular Chemistry of the Academy of Sciences of the Czech Republic, ISBN 978-80-85009-85-9, p. 85, 2016
D. Täuber, W. Cai, Y. Xia, O Inganäs, I.G. Scheblykin
