Radiative Recombination in Organic Solar Cells

• Applicants: Professor Dr. Carsten Deibel; Professor Dr.-Ing. Thomas Kirchartz; Professor Dr. Uwe Rau
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 254002545

The proposed project seeks to develop an improved understanding of radiative and non-radiative recombination processes in organic solar cells using electroluminescence spectroscopy and complementary characterization techniques. This goal requires us to first gain a solid understanding of the mechanism of radiative recombination in organic solar cells. We will approach it by performing very sensitive steady state as well as transient electroluminescence measurements on selected systems, and by interpreting the results aided by simulations based on trapping-and-release models. In a second step, we will apply our ability to interpret electroluminescence measurements to characterize a wider range of state-of-the-art organic solar cells. We will focus in our project on characterizing the role of localized states or traps on the performance, on studying the relation between the microstructure of the material and its density of states and on the difference in origin between radiative and non-radiative recombination processes. Furthermore, we will use electroluminescence spectroscopy to study the band tail states at the donor:acceptor interface, which have been shown to determine the open-circuit voltage in bulk-heterojunction solar cells. Finally, we will attempt to summarize our results by establishing fundamental limits for the efficiency of molecular solar cells, in order to develop guidelines for improving their power conversion efficiencies.

• DFG Programme: Research Grants