Dresden 2009 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 42: Poster Session II (Nanostructures at surfaces: arrays; Nanostructures at surfaces: Dots, particles, clusters; Nanostructures at surfaces: Other; Nanostructures at surfaces: Wires, tubes; Metal substrates: Adsorption of O and/or H; Metal substrates: Clean surfaces; Metal substrates: Adsorption of organic/bio moledules; Metal substrates: Solid-liquid interfaces; Metal substrates: Adsorption of inorganic molecules; Metal substrates: Epitaxy and growth; Heterogeneous catalysis; Surface chemical reactions; Ab-initio approaches to excitations in condensed matter; Organic, polymeric, biomolecular films– also with adsorbates; Particles and clusters)

O 42.40: Poster

Mittwoch, 25. März 2009, 17:45–20:30, P2

Charge transfer in the TCNQ-sexithiophene complex — •Kai-Felix Braun and Saw-Wai Hla — Nanoscale & Quantum Phenomena Institute and the Department of Physics & Astronomy, Ohio University, Athens, Ohio 45701,USA.

Molecular crystals from thiophene molecules can be doped with TCNQ-F4 molecules for use in all-organic opto-electronic and semiconductor devices. The charge transfer and the molecular orbital energy level formation in between these two organic molecules is investigated here by density functional theory calculations (DFT). The isolated molecules are calculated non-bonded and bonded together forming a charge transfer complex (CTC). The relaxed structure of the complex shows essentially coplanar and centered molecules with the α-sexithiophene rings tilted alternatingly by 4.8°. The bond formation of these molecules results in a charge transfers of ~0.4 e- from the α-sexithiophene to the TCNQ-F4 molecule. The HOMO-LUMO gap width is reduced as compared to the isolated molecules due to the newly formed orbitals in the CTC complex. Upon adsorption on a Au(111) surface electrons are transferred onto the molecule complex thereby causing the molecular levels to align asymmetric with respect to the charge neutrality level. The theoretical results for the single molecule and CTC layer are compared to experimental photoemission and scanning tunneling spectroscopy results. Journal of Chemical Physics 129 (2008), 064707.