Berlin 2024 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 36: Poster: Ultrafast Electron Dynamics at Surfaces and Interfaces

O 36.6: Poster

Dienstag, 19. März 2024, 18:00–20:00, Poster C

Time-resolved photoelectron spectroscopy of charge separation at the PTCDA/TiOPc heterointerface on Ag(111) — •Marcel Theilen, Alexa Adamkiewicz, Alexander Lerch, Robert Wallauer, and Ulrich Höfer — Philipps-University Marburg, Germany

A key element for charge separation in organic donor/acceptor heterostructures is the formation of charge transfer (CT) states at the interface between the donor and acceptor molecules. A promising model system for studying such excitonic states is the well-defined heterosystem of PTCDA/TiOPc/Ag(111), which we examine by means of time-resolved two-photon photoemission (2PPE). Based on previous 2PPE measurements, the charge carrier dynamics upon selective excitation of excitons in the molecular layers are dominated by transfer processes into the interface state (IS) between molecule and metal. Increasing the molecule-metal distance results in a more effective decoupling to the IS and a possible formation of CT excitons at the donor/acceptor interface. However, the previous 2PPE measurements couldn't access the population of the excited molecular states, which is possible by means of time-resolved photoemission orbital tomography (tr-POT), as it provides a direct insight into the momentum-space dynamics of the excited molecular states. Here we demonstrate our first measurements of the charge carrier dynamics it the 2 ML PTCDA/2 ML TiOPc heterosystem using tr-POT. We follow the momentum-space dynamics of the excited molecular states and see, according to the 2PPE measurements, a strong coupling to the IS between molecule and metal.

Keywords: organic donor/acceptor interfaces; time-resolved photoelectron spectroscopy; time-resolved photoemission orbital tomography