Special projects between Bavaria and Florida

Dr. C. Deibel

Exp. Physics VI
Universität Würzburg

Dr. Zhai

NanoScience Technology Center
University of Central Florida

Columnar Conductive Polymer Assembly for Efficient Organic Solar Cells

One of the most promising candidates for large-scale economical power generation is the organic photovoltaic device due to the low cost of materials and fabrication and the favourable energy balance. However, their power conversion efficiency (~5 %) is still low compared to typical inorganic solar cells and remains clearly behind the theoretical predictions. In the BacaTec funded collaboration of the University of Central Florida with the Bavarian Julius-Maximilians-University Würzburg, novel polythiophene-based organic semiconductors essentially supramolecular structures such as columnar conductive polymer assemblies will be synthesized. The charge generation and transport properties of these highly ordered systems will be investigated. Organic photovoltaic devices will be fabricated by blending with suitable electron accepting materials. We expected to initiate and develop a long term scientific collaboration, with the aim of developing organic photovoltaic devices clearly above the current power conversion efficiencies.

Final report


The project BaCaTec "Columnar Conductive Polymer Assembly for Efficient Organic Solar Cells" was concerned with the specific arrangement of polymer nanowires in bulk heterojunction solar cells. In the project the Zhai group has produced corresponding samples based on regioregular polyalkylthiophene self-assembled nanowires, which were processed into thin film. In the Deibel group, these layers were completed by vapor deposition of electrodes to complete devices, and characterised by means of timedependent charge transport measurements, especially the photo-CELIV (charge extraction by linearly increasing voltage) technique. It has been found that the currently processed nanowires grow in the wrong direction, parallel to the electrodes, not perpendicular as desired. For this reason, the measured charge carrier mobility were not higher but lower than in the disordered reference material. The solar cell measurements correspondingly showed lower efficiencies as compared with disordered cells. First steps to affect growth through electrode functionalisation have been tried and are still in progress.


From this fruitful cooperation, which is based on the BaCaTec project and also expressed by a scientific visit of Dr. Deibel in Florida, data suitable for scientific publication as well as a project proposal "Materials World Network: Charge Transport and Recombination in BHJ Ordered Conjugated Polymer become OPVs with Structures "of the DFG and NSF can be seen as output.The proposal was filed in mid-November for review.


We hope that we can strengthen this cooperation, which was triggered by the BaCaTec project cooperation, under the umbrella of the DFG and NSF.


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