Ultrafast Dynamics in Quasi-Dimensional Organic Molecular Crystals Self-Assembled Monolayers of Photochromic Molecules (English shop)

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This dissertation investigates the optical and electronic properties of organic molecular materials, focusing on ultrafast excitation dynamics in quasi-one-dimensional molecular crystals and the structural characterization of self-assembled monolayers containing photochromic molecules.

The first part examines excitonic and phononic processes in organic molecular crystals using MePTCDI as a model system. Employing ultrafast time-resolved spectroscopy, including transient absorption, degenerate four-wave mixing and time-resolved luminescence, the study investigates exciton relaxation, electronic dephasing and coherent molecular vibrations. The experimental findings reveal extremely rapid exciton relaxation processes occurring on femtosecond timescales and provide insights into the interaction between electronic excitations and lattice vibrations.

The second part explores self-assembled monolayers of azobenzene-functionalized molecules on gold surfaces. Scanning tunneling microscopy, infrared spectroscopy and second-harmonic generation are used to investigate molecular organization, structural properties and the conditions required for photochromic switching. The results demonstrate the formation of highly ordered molecular monolayers while identifying steric limitations that prevent photoisomerization in densely packed structures.

By combining ultrafast optical spectroscopy with molecular surface engineering, the dissertation contributes to the understanding of organic photophysics, exciton dynamics and photoresponsive molecular systems.