1. Helmholtz-Zentrum Berlin, Department of Renewable Energy, Nanooptical Concepts for PV, Hahn-Meitner-Platz 1, 14109 Berlin, GermanybFreie Universität Berlin, Department of Physics, Arnimallee 14, 14195 Berlin, Germany
2. Helmholtz-Zentrum Berlin, Department of Renewable Energy, Nanooptical Concepts for PV, Hahn-Meitner-Platz 1, 14109 Berlin, Germany