Berlin 2018 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 12: Ultrafast Electron and spin dynamics at interfaces II
O 12.4: Vortrag
Montag, 12. März 2018, 15:45–16:00, MA 005
Ultrafast electron transfer across a ZnO-organic interface — •Lukas Gierster1, Sesha Vempati1, Jan-Christoph Deinert1,2, Anton Zykov3, Stefan Kowarik3, Yves Garmshausen4, Stefan Hecht4, and Julia Stähler1 — 1Fritz-Haber-Institut Berlin, Dpt. Phys. Chem. — 2Helmholtz-Zentrum Dresden-Rossendorf — 3Humboldt-Universität zu Berlin, Dpt. of Physics — 4Humboldt-Universität zu Berlin, Dpt. of Chemistry
Combining organic molecules with inorganic semiconductors is a promising route towards novel optoelectronic devices, such as organic LEDs or photovoltaics [1]. The electron transfer across the hybrid interface is a crucial factor for the efficiency of such devices. We investigate this fundamental process at the ZnO/p-quinquephenyl pyridine (5P-Py) surface using time-resolved two-photon photoelectron spectroscopy. Upon adsorption of 5P-Py (mass equivalent of 2 ML) on ZnO (10-10) we find an occupied interfacial hybrid state close to the Fermi level. It can be used as an initial state to populate the molecular LUMO without direct excitation of the molecules. The LUMO population decays within 90 fs by electron transfer to ZnO. Furthermore, a bulk 5P-Py film (16 nm) was investigated, which was characterized by AFM and XRD showing a grainy and crystalline structure. Here, excitons were created by HOMO-LUMO excitation, which decay on a picosecond timescale due to exciton diffusion followed by charge separation at the interface as well as recombination. [1] N. Koch, ChemPhysChem 8, 1438-1455 (2007)