Hannover 2010 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 5: Femtosecond Spectroscopy I

MO 5.1: Vortrag

Dienstag, 9. März 2010, 14:00–14:15, F 102

Influence of TiO₂/Perylene Interface Modifications on Electron Injection and Recombination Dynamics — •Robert Schütz, Andreas F. Bartelt, Antje Neubauer, Rainer Eichberger, and Thomas Hannappel — Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin, Germany

Dye sensitized solar cells (DSSCs) operate by injecting electrons from the excited state of a light-harvesting dye into the continuum of conduction band states of a wide bandgap semiconductor. It is well known that the efficiency of DSSCs can be improved by controlling the interface energetics using molecular interface modifiers. Whereas this leads to a beneficial band level shifting, it also affects the interfacial electron injection and recombination dynamics. We used femtosecond transient absorption spectroscopy in the VIS region to demonstrate a retardation of the ultrafast injection and recombination dynamics by coadsorbing inert gases and solvents with increasing dipole moments on a TiO₂/perylene interface. Model perylene dyes with different electronic couplings to the colloidal TiO₂ films were subject to precisely defined chemical environments. While coadsorption of N₂ and Ar doubled injection times compared to UHV, introduction of solvents led to retardations of up to 2 orders of magnitude which correlates well with the degree of polarity of the chemical species. The ultrafast component of the nonexponential back electron transfer was significantly reduced with coadsorbant polarity.