Freiburg 2024 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 21: Ultrafast Dynamics II
MO 21.6: Vortrag
Donnerstag, 14. März 2024, 15:45–16:00, HS 3044
Symmetry-breaking charge transfer and intersystem crossing in copper phthalocyanine thin films — •Esther del Pino Rosendo1, Okan Yildiz2, Tomasz Marszalek2, Charusheela Ramanan3, and Paul W. M. Blom2 — 1Johannes Gutenberg-Universität. Staudingerweg 7, 55128 Mainz — 2Max Planck Institut für Polymerforschung. Ackermannweg 10 55128 Mainz — 3Vrije Universiteit Amsterdam. De Boelelaan 1105, 1081 HV Amsterdam
Intermolecular interactions in π-stacked chromophores strongly influence their photophysical properties, and thereby also their function in photonic applications. Mixed electronic and vibrational coupling interactions lead to complex potential energy landscapes with competitive photophysical pathways. The photoexcited dynamics of the small molecule semiconductor CuPc are characterized in solution as well as in thin film. In the thin film case, the material can organize in two different π-stacked architectures, α-CuPc and β-CuPc. In solution, CuPc undergoes ultrafast ISC to the triplet excited state. In the solid state, both α-CuPc and β-CuPc morphologies exhibit a mixing between Frenkel and charge-transfer excitons. We find that this mixing influences the photophysical properties differently, based on morphology. α-CuPc demonstrates symmetry-breaking charge transfer, which furthermore depends on excitation wavelength. This mechanism is not observed in β-CuPc. These results elucidate how molecular organization mediates the balance of competitive photoexcited decay mechanisms in organic semiconductors.
Keywords: Organic Chromophores; Transient Absorption Spectroscopy; Organic Semiconductors; Charge Transfer; Intersystem Crossing