Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 100: Organic electronics and photovoltaics
O 100.4: Vortrag
Freitag, 18. März 2011, 12:00–12:15, WIL B122
Tuning the hole-injection barrier at the organic-metal interface with a strong organic acceptor — •Jens Niederhausen1, Patrick Amsalem1, Johannes Frisch1, Andreas Wilke1, Benjamin Bröker1, Antje Vollmer2, Ralph Rieger3, Klaus Müllen3, Jürgen P. Rabe1, and Norbert Koch1 — 1Humboldt-Universität, Institut für Physik, Berlin, Germany — 2Helmholtz Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany — 3Max Planck Institut für Polymerforschung, Mainz, Germany
Ultraviolet photoelectron spectroscopy was used to investigate how pre-adsorption of the strong electron acceptor hexaazatriphenylene-hexanitrile (HATCN) on Ag(111) affects the energy level alignment of two subsequent deposited conjugated organic materials (COM). The tuning of the sample work function (WF) by precovering Ag(111) with HATCN monolayers oriented either in a lying or in a standing fashion is found to induce important variations in the hole injection barrier (HIB) of the COM. An interface dipole of similar magnitude is observed upon adsorption of both COM overlayers on a lying HATCN monolayer with low WF. It is related to the push-back effect, which occurs at specific adsorption sites of the molecules at very low coverage. For COM adsorbed on Ag(111) precovered with a standing HATCN monolayer with high WF, Fermi level pinning is identified in both cases, and appears as a fundamental limit to further HIB lowering. The observed behavior is reminiscent of the adsorption characteristics of COM on high WF conducting polymers substrates. This leads to a situation where the HIB decreases by up to 1.1 eV.