Investigation of interlayers for organic tandem solar cells 1)Investigation of the properties of doped solution processed interlayers for polymer tandem solar cells. 2)Development of polymer tandme solar cells with high efficiency.

• Applicant: Dr. David Wynands
• Subject Area: Experimental Condensed Matter Physics ; Experimental and Theoretical Physics of Polymers
• Term: from 2011 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 200476906

The planed research has four main parts1) Hybrid tandem solar cells with a polymer based bottom cell and a small molecule based cell on top will be prepared.The interlayer will consist of doped small molecule transport layers with standard dopants.These tandem solar cells act as reference system.2) Investigation of doped solution processed interlayers.Doping of solution processed layers has already been reported by some other groups. These concepts and dopants shall be adopted and applied to interlayers in tandem cells. Here, the used materials do not need to fullfill the requisite of transparancy but will be chosen from a variety of well known standard polymers. The focus is laid on understanding the key properties the interlayer material must have for being dopable, providing ohmic contact to the subcell, and for enabling a recombination without energy loss. 3) Search for and investigation of new transparent and dopable solution processed interlayers. After first progress with the reference materials has been made, the approach shall be enhanced by finding new transport materials for the interlayers, especially transparent ones. For this purpose, the results of the investigation of the reference materials may provide ideas for the synthesis of modified polymers. Also solution processing of small molecules that are already established as transport materials is considered as option. 4) It is the aim to finally realize a polymer tandem cell with high efficency, by using the developed doped interlayers. The state of the art best absorber materials, which provide complementary absorption of the two subcells, will be utilized. The interlayer materials have to be chosen on account of the previous investigations, in order to ensure ohmic contacts to the respective subcells. The design of the interlayers will be optimized in consideration of the optimal thickness and energy level matching to the absorber materials.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Dr. Alan J. Heeger