1. Department of Materials Science and Engineering, University of Washington, Box 352120, Seattle, Washington 98195-2120; Institut für Organische Chemie, Organische Chemie II, Universität Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany; Materials Ireland Polymer Research Centre, Department of Physics, Trinity College, University of Dublin, Dublin 2, Ireland; and Humboldt Universitaet, Institut fuer Physik, Lehrstuhl Photobiophys, Invalidenstrasse 110, D-10115, Berlin, Germany