Regensburg 2010 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 48: Surface dynamics I

O 48.9: Vortrag

Mittwoch, 24. März 2010, 12:30–12:45, H40

Electronic structure and charge carriers dynamics in 6T absorbed on Au(111). — •Erwan Varene, Isabel Martin, Martin Wolf, and Petra Tegeder — Freie Universitaet Berlin, Fachbereich Physik, Arnimallee 14, 14195

Two-photon photoemission (2PPE) spectroscopy is employed to gain insight into the electronic structure as well as the charge carriers dynamics at the sexithiophene (6T)/Au(111) interface. This oligothiophene was chosen because it serves as a model system for the more structurally disordered polythiophene. These materials are used as electron donors in organic photovoltaic cells and organic field effect transistors. We observed the formation of an interface dipole of -0.8 eV and we found the highest occupied molecular orbital (HOMO) to be located 1.5 eV below the Fermi level (EF). In addition, we resolved two unoccupied states at 1.2 eV and 3 eV with respect to EF. The state 1.2 eV exhibiting a long lifetime of 500 fs can be assigned to an exciton. The state at 3 eV originates from the LUMO+1, possessing a lifetime of about 150 fs.