Light trapping, organic solar cells

Abstract In solar applications microstructured polymer surfaces can be used as optically functional devices. Examples are antireflective surfaces, dayUghting, sun protection systems, concentrator photovoltaic modules and light trapping structures in organic solar cells. The examples and the principles of function of the respective microstmctures are described in detail. The suitability of different manufacturing methods is discussed. Two of them, ultraprecision machining and interference lithography are described. For the latter experimental results are shown. Finally, the opportunities and the risks of the shown approaches are discussed. 

Folded solar cell architectures In order to benefit from the enhanced light absorption under the illumination at inclined incident angles, folded solar cell architectures have been developed for organic solar cells [24] (Fig. 9). An additional - and no less pronounced - light-trapping effect is due to multiple reflections and absorptions. Using substrates with a three-dimensional surface topography at the micrometer scale allows one to realize compact and flexible solar cells. Different... 

M. Niggemann, M. Riede, A. Gombert, K. Leo, Light trapping in organic solar cells, Phys. Status Solid A 205 (2008) 2862-2874. 

Improved Carrier Extraction by Intercalating Membranes. With light trapping, the condition for good extraction of electrons and holes requiring Le,h l, is also relaxed, since a smaller thickness of the solar cell is possible. For low mobility organic materials, this condition is still a problem. It ensures that electrons and holes generated in the absorber reach the membrane within their recombination lifetime. They can then pass into the external circuit. The distance of the membranes, however, is not limited by the thickness l of the absorber, as can be seen in Fig. 4.11, and can be made arbitrarily short. 

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