Dresden 2014 – scientific programme

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O: Fachverband Oberflächenphysik

O 77: Focussed Session: Towards a Quantitative Understanding of Complex Adsorption Structures: Surface Science goes Organic III

O 77.6: Talk

Thursday, April 3, 2014, 17:30–17:45, TRE Phy

Combined 2PPE and photoluminescence study of electron and exciton dynamics at the PTCDA/Ag(111) interface — •Andreas Namgalies, Manuel Marks, Sangam Chatterjee, and Ulrich Höfer — Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität Marburg, D-35032 Marburg

The presence of a metal contact can drastically alter the electron and exciton dynamics of organic semiconductors. For a study of the fundamental processes that govern this dynamics as well as the dynamics of carrier transfer at the metal/organic interface, we combine the advantages of time resolved 2-photon-photoemission (2PPE) and time-resolved photoluminescence in one experiment and investigate well-ordered and characterized thin films of PTCDA/Ag(111). Our luminescence setup enables monolayer sensitivity and a time resolution of approximately 700 fs using a streak camera.

It will be shown that a long-lived component of hot electrons in the 2PPE spectrum, whose lifetime and intensity strongly increases as a function of layer thickness, arises at the metal interface as a result of exciton decay of PTCDA. Systematic studies as a function of film thickness reveal, that Foerster-like dipole-dipole coupling is important for the decay in the regime of several monolayers, whereas exciton hopping between PTCDA layers and quenching and the interfaces dominates the decay for thicker films.