Résumé des résultats (Abstract)
(Anglais)
|
The project aims at the improvement of organic materials for optoelectronic applications, such as photonic antennae, LEDs, lasing microcavities, and electro-optic modulators. The difficulties met with conventional polymer-based organic materials (e.g., limited stability and detrimental inter chain interactions) are overcome by the design of highly ordered and well defined materials with full control of intermolecular interactions, making use of the unique properties of oligomeric conjugated molecules encapsulated in host compounds (e.g., host-guest compounds (HGCs) of oligophenylenevinylenes and oligothiophenes with zeolites and perhydrotriphenylene).
By molecular and supramolecular engineering, the desired properties are obtained: improved chemical stability (by exclusion of oxygen), high fluorescence quantum yields (by avoiding molecular aggregation), color tuning (by variation of conjugation length and substituents), intrinsic polarisation (uniaxial systems), high lasing efficiencies (e.g., by doping with long wavelength emitters), enhanced energy and electron transfer (by low-dimensional, highly ordered systems with small, controllable intermolecular distances), energy funnelling (by spatially separating energy donor and acceptor molecules), and high NLO efficiencies (microscopic order on macroscopic scale). The HGCs are structurally characterised by XRD, optical methods using polarised light and by atomic microscopies. NLO efficiencies and luminescence properties are investigated. The rates of electron and energy transfer are determined by fluorescence spectroscopy with fem to second time resolution and spatial resolutions down to the single-molecule level. Theoretical calculations of molecular properties and intermolecular interactions (dipolar coupling, energy and charge transfer rates) will lead to a detailed understanding of the structure-property relationships of HGCs. The technological potential of the materials for device fabrication is explored.
|
