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?-Stacks in Organic Crystals: Spectroscopic Signatures of Excimer Formation

Seminar by Johannes Gierschner, Mons, Belgium.

Abstact:
The establishment of thorough structure-property relationships for conjugated organic materials is of crucial importance in the design of (opto-)electronic devices. Among the structures, cofacial arrangements have gained considerable interest due to the changes of directionality and extent of charge and energy transport in columnar p-stacks, as well as their role as trap states for luminescence due to their excimer-like nature. The lecture will provide insight into the spectroscopic signatures of excimer states in molecular crystals in a combined experimental and theoretical approach, to elucidate the absorption and emission bandshapes, energetic positions, and deactivation pathways. In order to establish the implications of the arrangements to spectroscopy, model dimers and nano-sized single crystals are investigated. Size effects on absorption, light scattering and emission properties are discussed and comparisons are made with alternative packing motifs, e.g. 'herringbone' or 'brickstone' architectures.