This contribution is dedicated to Prof. Frank Willig. The dynamics of heterogeneous electron transfer between chemisorbed photosensitizers and semiconductors is strongly governed by the electronic coupling between molecular adsorbate and solid substrate mediated by molecular anchor and spacer groups. In the first part of the talk, I will review a systematic study of the charge transfer dynamics in photovoltaic perylene-spacer-anchor-TiO2 model systems performed in Frank Willig's group. In particular, electron transfer dynamics of perylene dyes with two different anchor groups, carboxylic and phosphonic acid, as well as sp3-  and sp2-hybridized spacer groups are compared [1,2].  Both forward (injection) as well as ultrafast backward (recombination) electron transfer show profound dependence on the chemical nature of the anchor-cum-spacer groups. Electronic structure calculations provide a microscopic explanation of the differences in electronic coupling.In the second part of the talk, I will discuss recent pump-probe reflectivity measurements on TiO2. Ultrafast electronic interband excitation with 5 eV photon energy induces a large-amplitude coherent optical phonon with a phase shift of -0.2 p compared to an instantaneous cosine-like displacive excitation. The dynamic evolution of the potential energy surface minimum of the coherent phonon coordinate is explored using accurate density functional theory calculations, which con?rm a shift of the potential energy surface minimum upon resonant laser excitation and reveal a signi?cant positive contribution to the displacive force due to the cooling of the excited hot electron-hole plasma on the few-femtosecond time scale [3].[1] R. Ernstorfer et al., J. Phys. Chem. B 110, 25383 (2006).[2] P. Persson, J. Chem. Theory Comput. 2, 441 (2006).[3] E.M. Bothschafter et al., Phys. Rev. Lett. 110, 067402 (2013).

Chemical control of heterogeneous electron transfer dynamics and strong electron-lattice couplingin TiO<sub>2</sub>

246th National Meeting (2013)

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Chemical control of heterogeneous electron transfer dynamics and strong electron-lattice couplingin TiO2

Chemical control of heterogeneous electron transfer dynamics and strong electron-lattice couplingin TiO₂