Dresden 2006 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 23: POSTER Functional Organic Thin Films
CPP 23.10: Poster
Donnerstag, 30. März 2006, 17:00–19:00, P2
Energy Level Alignment at Dihexylsexithiophene-Metal Interfaces — •Steffen Duhm1, Hendrik Glowatzki1, Robert L. Johnson2, Jürgen P. Rabe1, and Norbert Koch1 — 1Humboldt-Universität zu Berlin, Institut für Physik, Newtonstr. 15, D-12489 Berlin — 2Universität Hamburg, Institut für Experimentalphysik, Luruper Chaussee 149, D-22761 Hamburg
The energy level alignment at metal-organic interfaces is a key issue for improving the performance of novel organic (opto-) electronic devices. In certain cases, solution-based processing of organic materials is preferred over vacuum sublimation. Frequently, alkyl side-chains are attached to the conjugated moieties for improved solubility. To investigate the influence of alkyl side-chain addition on interface energetics, we studied interfaces formed between the organic molecules sexithiophene (6T) and α,ω-dihexylsexithiophene (DH6T) and the metal surfaces Ag(111) and polycrystalline Au using ultraviolet photoelectron spectroscopy (UPS). Morphology was investigated with Atomic Force Microscopy (AFM) in ultra-high-vacuum. Interestingly, we observed significantly lower hole injection barriers (0.6 eV) for DH6T on the metal surfaces than for 6T. We explain this behavior in terms of the molecular orientation. In addition, we demonstrate that the hole injection barrier at interfaces between DH6T and metals can be further reduced by the insertion of (sub)monolayers of the strong electron acceptor tetrafluoro-tetracyanoquinodimethane (F4-TCNQ).