1. LTCI, Institut Polytechnique de Paris, Télécom Paris, 46 rue Barrault, 75013 Paris, France
2. Materials Department, University of California Santa Barbara, Santa Barbara, California 93106, USA
3. Institute for Energy Efficiency, University of California Santa Barbara, Santa Barbara, California 93106, USA
4. Center for Opto-electronic Materials and Devices, Korea Institute of Science and Technology, Seoul 02792, South Korea
5. Department of Electrical and Computer Engineering, University of California Santa Barbara, Santa Barbara, California 93106, USA
6. Center for High Technology Materials, University of New-Mexico, 1313 Goddard St. SE, Albuquerque, New Mexico 87106, USA