Berlin 2024 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 46: Focus Session: Ultrafast Processes in Organic Semiconductors and Perovskites II (joint session O/CPP)

CPP 46.11: Vortrag

Donnerstag, 21. März 2024, 17:45–18:00, MA 004

Calculation of Diffusion Properties of Molecular Excitons based on Static Optical Spectra — •Chris Rehhagen and Stefan Lochbrunner — University of Rostock, Institute of Physics

The understanding of the mobility of molecular excitons is fundamental for the use of molecular systems in organic solar cells. Especially a small diffusion length is a bottleneck still limiting the efficiency of light harvesting devices. Often, the diffusion constant of molecular excitons is determined by experimental methods observing e.g. exciton-exciton interaction or quenching processes. Additionally, advanced theoretical tools are used for prediction. In both cases, the effort is significant. In this work, we present a method to predict the exciton diffusion constant using static absorption and emission spectra in combination with basic geometric information of the system. Based on Försters theory the diffusion constant can be calculated from the spectral overlap and the electronic coupling. Both properties can be determined from static spectra based on the methods given in the scientific literature. We analyze these methods in detail. Then, the results are compared with experimentally determined diffusion constants in four different PBI-based solid state systems investigated in our group previously, including one-dimensional aggregates, extended nanoparticles and single crystals. In all cases, we find consistency between the experimental results and our prediction.

Keywords: molecular excitons; exciton diffusion; electronic coupling; Förster transfer