Epitaxial Growth of pi Stacked Perfluoropentacene on Graphene Coated Quartz

Chemical vapor deposited large area graphene is employed as the coating of transparent substrates for the growth of the prototypical organic n type semiconductor perfluoropentacene PFP . The graphene coating is found to cause face on growth of PFP in a yet unknown substrate mediated polymorph, which is solved by combining grazing incidence X ray diffraction with theoretical structure modeling. In contrast to the otherwise common herringbone arrangement of PFP in single crystals and standing films, we report a amp; 960; stacked arrangement of coplanar molecules in flat lying films, which exhibit an exceedingly low amp; 960; stacking distance of only 3.07 , giving rise to significant electronic band dispersion along the amp; 960; stacking direction, as evidenced by ultraviolet photoelectron spectroscopy. Our study underlines the high potential of graphene for use as a transparent electrode in opto electronic applications, where optimized vertical transport through flat lying conjugated organic molecules is desire