1. IEK5‐PhotovoltaicsForschungszentrum Jülich 52425 Jülich Germany
2. Institute of Physics and AstronomyUniversity of Potsdam Karl‐Liebknecht‐Str. 24‐25 D‐14476 Potsdam‐Golm Germany
3. Faculty of Engineering and CENIDEUniversity of Duisburg‐Essen Carl‐Benz‐Str. 199 47057 Duisburg Germany