Dresden 2006 – scientific programme

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SYET: Dynamics of electron transfer processes at surfaces

SYET 1: Dynamics of electron transfer processes at surfaces

SYET 1.6: Invited Talk

Thursday, March 30, 2006, 12:30–13:00, HSZ 04

Time-resolved electron injection from the excited state of anchored molecules into semiconductors — •Frank Willig¹, Lars Gundlach¹, Ralph Ernstorfer¹, Volkhard May², Petter Persson³, Rainer Eichberger¹, and Silke Felber¹ — ¹Hahn-Meitner-Institute, SE4, Glienickerstrasse 100, 14109 Berlin, Germany — ²Humboldt Universität, Institut für Physik, Newtonstrasse 15, 12489 Berlin, Germany — ³Uppsala University, Quantum Chemistry, Box 518, SE-75120 Uppsala, Sweden

The chromophore perylene was covalently attached to the anchor groups carboxylic acid and phosphonic acid. These molecules were further modified by inserting different spacer groups. The anchor groups formed strong chemical bonds with the semiconductors TiO2 and ZnO. The adsorption geometry was predicted on the basis of DFT calculations and checked with angle and polarization dependent two-photon photoemission (2PPE) signals. The above complex molecules were adsorbed from solution in a dedicated ultra-high-vacuum (UHV) chamber. The characteristic time for transferring the electron from the excited state of the chromophore to empty acceptor states of the semiconductor was measured with 2PPE and with transient absorption. The experimental electron transfer times were compared with line widths obtained from DFT calculations and from fit curves to the linear absorption spectra. The initial energy distribution of the injected electrons represents the heterogeneous electron transfer spectrum. The measured shape of the distribution agreed with the theory for heterogeneous electron transfer in the so called wide band limit.