1. Advanced Materials Engineering and Modelling Group, Faculty of Chemistry, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, Wroclaw 50-370, Poland
2. Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, Fife KY16 9SS, U.K.
3. Laboratoire PEIRENE EA 7500, Faculté des Sciences et Techniques, 123, Avenue Albert Thomas, Limoges cedex 87060, France