Tuning hole-injection barriers at organic/metal interfaces exploiting the orientation of a molecular acceptor interlayer

J. Niederhausen,1 P. Amsalem,1 J. Frisch,1 A. Wilke,1 A. Vollmer,2 R. Rieger,3 K. Mullen,3 J. P. Rabe,1 and N. Koch1,2,* 1Humboldt-Universitat zu Berlin, Institut fur Physik, Newtonstr. 15, DE-12489 Berlin, Germany 2Helmholtz Zentrum Berlin fur Materialien und Energie GmbH BESSY II, Albert-Einstein-Str. 15., DE-12489 Berlin, Germany 3Max Planck Institut fur Polymerforschung, Ackermannweg 10, DE-55128 Mainz, Germany (Received 24 April 2011; revised manuscript received 1 August 2011; published 3 October 2011)