1. Cavendish Laboratory University of Cambridge 19, JJ Thomson Avenue Cambridge CB3 0HE UK
2. Institute for Photovoltaics (ipv) University of Stuttgart Pfaffenwaldring 47 70569 Stuttgart Germany
3. Helmholtz Young Investigator Group FRONTRUNNER IEK5-Photovoltaik Forschungszentrum Jülich 52425 Jülich Germany
4. CINBIO Universidade de Vigo Materials Chemistry and Physics Group Department of Physical Chemistry Campus Universitario Lagoas, Marcosende 36310 Vigo Spain
5. Department of Materials Imperial College London Exhibition Road London SW7 2AZ UK