1. I. Institute
of Physics (IA), ‡Institute for Theoretical Solid State Physics, and §JARA-Fundamentals
of Future Information Technology, RWTH Aachen University, 52056 Aachen, Germany
2. Department of Electrical
Engineering, Princeton University, Princeton, New Jersey 08544, United States
3. National Center for Photovoltaics, National Renewable Energy Laboratory, Golden, Colorado 80401, United States