Regensburg 2022 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 39: Molecular Electronics and Excited State Properties
CPP 39.6: Vortrag
Donnerstag, 8. September 2022, 12:45–13:00, H38
Temperature Dependent Optical Transition in Zinc Phthalocyanine Single Crystals — •Lisa Schraut-May1, Sebastian Hammer1, Kilian Frank2, Bert Nickel2, and Jens Pflaum1,3 — 1Experimental Physics VI, Julius Maximilian University, 97074 Würzburg — 2Department of Physics and Center for Nano Science, Ludwig Maximilian University, 80539 Munich — 3Bavarian Center for Applied Energy Research, 97074 Würzburg
By its various polymorphs, Zinc Phthalocyanine (ZnPc) serves as an excellent model system to study the interplay between molecular packing on microscopic length scales and the resulting photophysical properties [1]. Here, we address the dependence of the excitonic coupling on the underlying crystal structure of the thermodynamically stable ZnPc β-phase. For this purpose, we conducted complementary temperature dependent X-ray diffraction as well as polarisation dependent photoluminescence (PL) studies on ZnPc single crystals. By means of the PL signals spectral characteristics we observed a continuous transition from a J- into an H-aggregated state between 300 K and 100 K. Remarkably, below 100 K an exceptionally sharp PL peak evolves being indicative for the formation of a superradiant J-aggregate. As there is no indication for a discrete structural phase transition, we interpret the resulting PL signal in this temperature range by a model of vibronically coupled excitons steered by the gradual anisotropic thermal contraction of the crystal lattice [2]. We thank the Bavarian research network SolTech for financial support. [1] Hammer et al., Appl. Phys. Lett. (2019) [2] Hestand et al., Chem. Rev. (2018)