Dresden 2020 – scientific programme

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O: Fachverband Oberflächenphysik

O 6: Organic Molecules on Inorganic Substrates I: Electronic, Optical and other Properties

O 6.2: Invited Talk

Monday, March 16, 2020, 10:45–11:15, REC C 213

Excited State Dynamics at Interfaces with Organic Semiconductors — •Petra Tegeder — Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Germany

Understanding the dynamics of electronically excited molecular states after optical excitation in organic semiconductors is necessary for improvement and optimization of potential molecule-based devices such as organic photovoltaic cells or organic light emitting diodes. Using femtosecond time-resolved spectroscopies, namely two-photon photoemission (2PPE) and second harmonic generation (SHG) we studied the excited state dynamics at interfaces and within thin films of several organic semiconducting molecules. This includes the singlet fission dynamics in triisopropyl-silylethynyl-pentacene (TIPS-Pn) adsorbed on Au(111). Based on 2PPE measurements we proposed a coherent excitation of the singlet and multiexciton state, both decaying with the same time constant of 160 fs. The triplet state stabilizes on a time scale of 1.6 ps and decays to the ground state. The latter occurs within 620 ps. However, SHG measurements on TIPS-Pn films point towards a non-coherent formation of the singlet and multiexciton state. In well-ordered diindenoperylene (DIP) and perylene alkyldiimide (PDIR) films, respectively, and at differently structured DIP/PDIR interfaces we elucidated the exciton and charge transfer dynamics in the femtosecond regime using SHG.