title: Charge Transfer Dynamics at Dye-Sensitized ZnO and TiO2 Interfaces Studied by Ultrafast XUV Photoelectron Spectroscopy.
abstract: Interfacial charge transfer from photoexcited ruthenium-based N3 dye molecules into ZnO thin films received controversial interpretations. To identify the physical origin for the delayed electron transfer in ZnO compared to TiO2, we probe directly the electronic structure at both dye-semiconductor interfaces by applying ultrafast XUV photoemission spectroscopy. In the range of pump-probe time delays between 0.5 to 1.0 ps, the transient signal of the intermediate states was compared, revealing a distinct difference in their electron binding energies of 0.4 eV. This finding strongly indicates the nature of the charge injection at the ZnO interface associated with the formation of an interfacial electron-cation complex. It further highlights that the energetic alignment between the dye donor and semiconductor acceptor states appears to be of minor importance for the injection kinetics and that the injection efficiency is dominated by the electronic coupling.
authors.affiliation: Joint Laboratory for Ultrafast Dynamics in Solutions and at Interfaces (JULiq), Institute of Methods for Material Development, Helmholtz-Zentrum Berlin, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany.|Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
authors.forename: Mario
authors.initials: M
authors.lastname: Borgwardt
authors.affiliation: Joint Laboratory for Ultrafast Dynamics in Solutions and at Interfaces (JULiq), Institute of Methods for Material Development, Helmholtz-Zentrum Berlin, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany.|Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Wilke
authors.affiliation: SPECS Surface Nano Analysis GmbH, Voltastrasse 5, D-13355 Berlin, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Kampen
authors.affiliation: SPECS Surface Nano Analysis GmbH, Voltastrasse 5, D-13355 Berlin, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Mähl
authors.affiliation: School of Chemistry, Monash University, Clayton 3800, VIC, Australia.
authors.forename: Manda
authors.initials: M
authors.lastname: Xiao
authors.affiliation: School of Chemistry, Monash University, Clayton 3800, VIC, Australia.
authors.forename: Leone
authors.initials: L
authors.lastname: Spiccia
authors.affiliation: Institute of Solar Fuels, Helmholtz-Zentrum Berlin, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany.
authors.forename: Kathrin M
authors.initials: KM
authors.lastname: Lange
authors.affiliation: Joint Laboratory for Ultrafast Dynamics in Solutions and at Interfaces (JULiq), Institute of Methods for Material Development, Helmholtz-Zentrum Berlin, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany.|Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
authors.forename: Igor Yu
authors.initials: IY
authors.lastname: Kiyan
authors.affiliation: Joint Laboratory for Ultrafast Dynamics in Solutions and at Interfaces (JULiq), Institute of Methods for Material Development, Helmholtz-Zentrum Berlin, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany.|Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
authors.forename: Emad F
authors.initials: EF
authors.lastname: Aziz