1. Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, School of Basic Sciences, Swiss Federal Institute of Technology, CH-1015 Lausanne, Switzerland, Centre for Electronic Materials and Device, Department of Chemistry, Imperial College London, Exhibition Road, SW7 2AZ London, U.K., and Institut de Ciencia Molecular (IcMol), Universitat de Valencia, 46100-Burjassot, Valencia, Spain