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O: Fachverband Oberflächenphysik

O 88: Focus Session: Ultrafast Processes in Organic Semiconductors and Perovskites II (joint session O/CPP)

O 88.10: Talk

Thursday, March 21, 2024, 17:30–17:45, MA 004

Interrelation between excimer dynamics and crystal structure of molecular solids: The case of perylene and perfluorotetracene — •Dominik Muth, Anton Krüger, Sebastian Anhäuser, Daniel Bischof, Gregor Witte, and Marina Gerhard — Department of Physics and Material Sciences Center, Philipps-Universität Marburg, Germany

Excimer formation in organic semiconductors has been known for approximately 70 years. The phenomenon has, however, recently attracted increased interest due to potential applications in the fabrication of organic white light emitting diodes. Gaining insight into the process of excimer formation in molecular solids and controlling the excimer properties via the intermolecular arrangement is therefore of great interest, also from a fundamental point of view.

In this work, we investigate the excimer dynamics in single crystals of two organic semiconductors, i.e. the prototypical material perylene as well as perfluorinated tetracene via time resolved photoluminescence spectroscopy. For both materials, two different polymorphs are studied, providing insight into the influence of the molecular packing on the formation of excimers. Beside the excimer signatures, resolving the dynamics on a picosecond time scale allows us to explore short-lived higher energetic features, which potentially originate from precursor states of excimers. Varying the temperature from 10 to 295 K as well as determining the polarization of the emitted signatures reveals thermal barriers for the population of certain states and the orientation of the underlying transition dipole moments.

Keywords: Excimer; Perylene; Perfluorotetracene; Molecular Crystals; Time resolved photoluminescence spectroscopy