Dresden 2020 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 49: Poster Session II
CPP 49.29: Poster
Tuesday, March 17, 2020, 14:00–16:00, P1A
Directly probing the singlet-triplet dynamics in organic semiconductors by high intensity step-function photoexcitation — •Jonas Gehrig1, Ulrich Müller1, Lena Roos2, Anke Krueger2, and Jens Pflaum1,3 — 1Experimental Physics VI, Julius Maximilian University of Würzburg, 97074 Würzburg — 2Institute of Organic Chemistry, Julius Maximilian University of Würzburg, 97074 Würzburg — 3ZAE Bayern, 97074 Würzburg
The excitonic singlet-triplet dynamics of organic semiconductors play a crucial role for their efficient implementation in opto-electronic devices. We present a compact setup to probe the relevant time-dependent processes like inter-system crossing, singlet fission (SF) or thermally activated delayed fluorescence (TADF). Unlike single molecule spectroscopy or pump-probe techniques, we utilize step-function photoexcitation at high excitation intensities in combination with time correlated single photon counting. Applying this technique to neat single crystals of tetracene (Tc) and its 2,2'-ditetracene dimer (DTc) we observed a sub-ns SF in Tc while this process is efficiently suppressed in DTc. X-ray diffraction analysis in combination with theoretical coupled-cluster calculations attribute this striking difference to the respective crystal structure being slightly modified by the covalent linking at the DTc 2,2'-position. On the molecular level, represented by doped anthracene single crystals, the fluorescent properties of Tc and DTc are almost identical and the absence of SF in both host-guest-systems emphasizes the role of inter- rather than intramolecular interactions for this non-radiative decay process.