1. Molecular Neurobiology, MBB, Karolinska Institutet, SE-171 77 Stockholm, Sweden, Organic Electronics, ITN, Linköping University, SE-601 74 Norrköping, Sweden, Organic Physics, ITN, Linköping University, SE-601 74 Norrköping, Sweden, and Applied Physics, IFM, Linköping University, SE-581 83 Linköping, Sweden