Optical constants of conjugated polymer/fullerene based bulk-heterojunction organic solar cells

The performance of organic solar cells consisting of multiple layers, which are a few hundred nanometers thick, is determined by strong optical interference effects. In order to model their optical and photoelectrical behavior, we determined the optical constants of all components of this system. This was done by fitting model dielectric functions to reflection and transmission spectra of all layers in the solar cell device. We put a special emphasis on understanding the optical behavior of the photoactive bulk heterojunction film, which consists of a composite of semiconducting polymers with fullerenes.