1. Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands, Stratingh Institute and MSC, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands, and Christian Doppler Laboratory for Plastic Solar Cells, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria