1 Biomolecular and Organic Electronics, Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping, Sweden. Electronic address: qingzhen.bian@liu.se.
2 Biomolecular and Organic Electronics, Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping, Sweden.
3 Laboratory of Organic Electronics, Department of Science and Technology, Linköping University, 60174 Norrköping, Sweden.
4 Molecular Surface Physics and Nano Science, Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping, Sweden.
5 Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping, Sweden.
6 Biomolecular and Organic Electronics, Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping, Sweden. Electronic address: olle.inganas@liu.se.