Regensburg 2019 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 3: Molecular Electronics and Excited State Properties

CPP 3.6: Vortrag

Montag, 1. April 2019, 11:00–11:15, H13

Polarized absorbance and Davydov splitting in bulk and thin-film pentacene polymorphs — •Caterina Cocchi¹, Tobias Breuer², Gregor Witte², and Claudia Draxl¹ — ¹Physics Dept. and IRIS Adlershof, Humboldt-Universität zu Berlin, Germany — ²Faculty of Physics, Philipps-Universität Marburg, Germany

Pentacene is one of the most studied organic materials but a number of issues related to it are still debated. One of them concerns the role of polymorphism and its effects on the lowest-energy excitations, appearing in the visible region and being subject to a sizable Davydov splitting. We address this problem in a combined theoretical and experimental work, where the electronic and optical properties of three pentacene phases (two bulk polymorphs and the thin-film phase) are investigated. Optical spectra computed from many-body perturbation theory are compared with the polarization-resolved absorbance. In this way, the two Davydov components of the first exciton are identified along with the optical fingerprints of each considered phase. All polymorphs exhibit common features at the absorption onset, while phase-dependent characteristics appear only above 2 eV. We discuss the character of the lowest-lying singlet and triplet excitons, highlighting the contributions from the electronic bands as well as the role of electron-hole interaction and local-field effects [1].

[1] C. Cocchi T. Breuer, G. Witte, and C. Draxl Phys. Chem. Chem. Phys. DOI: 10.1039/C8CP06384B (2018).