Building Blocks for Organic Electronics and Light-Responsive Materials

The first project (a collaboration with Dr. Moufdi Hadjab) is focused on studying small conjugated molecules consisting of diketopyrrolopyrrole, benzothiadoazole, thiophene, furan or naphthalene diimide units and their combinations. We are interest in characterization of optical, electronic and transport properties of these building blocks when they are organized into supramolecular structures: Crystals, semicrystalline polymeric fibers or self-assembled carpets on metals or semiconductive surfaces.

As one example of the ongoing studies, Figure depicts the structures of the adsorption layers of furan-flanked diketopyrrolopyrrole on graphite surface. The ordering is dependent, as seen from this illustration, one the method of thin-film formation: the vacuum deposition leads to more structured carpets (a), as compared to spin-coated samples (b). Computer simulation approach helps also to understand the role of the conformation (cis-cis, cis-trans or trans-trans) on the molecular ordering.

The second project (PI Markus Koch, a collaboration with Prof. Dr. Svetlana Santer) is a multiscale approach to the light-responsive matter. Azobenzenes, endowing inert matrices with light-sensitivity, and their isomers are the main objects of computations.

Azobenzenes having non-conventional geometries, like stars shown in Figure, possess unique molecular properties: Both isolated molecules can be in several isomerization states, and the ordered cylinders made of all-trans stars can loose their shape and functions upon UV light. More interesting phenomena are observed in azobenzene-containing polymer systems and self-assembled azobenzene monolayers. More information can be found here.