1. School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, College of Optics and Photonics: CREOL and FPCE, and Department of Physics, University of Central Florida, Orlando, Florida 32816-2700, and Institute of Solid-State Physics, Graz University of Technology, Petergasse 16, A-8010 Graz, Austria