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O: Fachverband Oberflächenphysik

O 78: Focus Session: Ultrafast Processes in Organic Semiconductors and Perovskites I (joint session O/CPP)

O 78.1: Topical Talk

Donnerstag, 21. März 2024, 10:30–11:00, MA 004

Transport and trapping in molecular materials at the picosecond time scale — •Marina Gerhard — Department of Physics and Material Sciences Center, Philipps-Universität Marburg, Germany

The Excitonic character of photoexcited states and the soft lattice of organic semiconductors pose guidelines for the design of devices, which are substantially different from those of their inorganic counterparts. To exploit the benefits of organic semiconductors, it is essential to comprehend the fate of photogenerated excitons at early times after their generation. In this context, molecular materials with a well-defined structure serve as ideal model systems to study processes such as exciton transport, excimer formation, singlet fission and energetic funneling. This contribution focuses on two recent studies, in which we explore the exciton dynamics in molecular systems using time and spatially resolved photoluminescence spectroscopy. For tetracene, the transport of excitons is driven by the interplay between singlet fission and triplet fusion. We demonstrate that this peculiar transport mechanism shows a pronounced temperature dependence and that it is severely hampered by the presence of trap states. The second study investigates heterostructures comprised of anthradithiophene with small concentrations of pentacene, which can efficiently mediate singlet fission through a favorable energy level arrangement of both compounds, demonstrating a system in which exciton funneling opens the possibility to spatially and spectrally separate light harvesting and singlet fission moieties.

Keywords: organic semiconductors; time-resolved photoluminescence spectroscopy; singlet fission; excimer formation; exciton transport