1. Department of Physics and Astronomy; University of Florence and LENS; Via Sansone 1 I-50019 Sesto Fiorentino (FI) Italy
2. C.H.O.S.E. (Centre for Hybrid and Organic Solar Energy); Department of Electronic Engineering; University of Rome Tor Vergata; Via del Politecnico 1 I-00133 Rome Italy
3. Istituto Italiano di Tecnologia; Graphene Labs; Via Morego 30 I-16163 Genova Italy
4. Center of Materials Technology and Photonics & Electrical Engineering Department, School of Applied Technology; Technological Educational Institute (T.E.I) of Crete; Heraklion 71 004 Crete Greece