Organic semiconductors

In recent years, physical chemists at University of Cologne have devoted their research on the emerging field of “organic electronics”. The active materials in this field are aromatic compounds with semiconducting properties. Material classes involve small molecules that can be vapour-deposited and short-chain oligomers as well as polymers for solution processing. Typical device types include organic light-emitting diodes (OLED), organic solar cells (OSC), organic field-effect transistors (OFET), and organic memories (OMEM). The Center for Organic Production Technologies (COPT) will enable the transfer of new results and concepts into technological advancement.

“Crosslinkable semiconductors” can be processed just like ordinary photoresists. This class of materials is very successful in fabrication of multilayered OLED with improved performance and extended lifetimes, microdisplays with RGB subpixels on the micron scale, and hole-conductive nanofoams for improved light outcoupling. By using a special spray-coating technique, optical lens arrays and diffractive optics elements are implemented into the OLED, giving rise to efficient light guiding.

In the field of solar cells the focus is on strongly absorbing materials such as low-molecular-weight dyes as well as poly(3-hexylthiophene) and various low-bandgap polymers. Here, the molecular orientation and ?-packing of organic semiconductors in the (mostly amorphous) bulk as well as at organic-organic and organic-metal interfaces are of paramount importance. An in-depth characterization of the molecular arrangement will be studied by various scanning-probe techniques.

Recently, graphene and graphene-like molecules have attracted a lot of attention also in the field of organic electronics, e.g. as replacement for the transparent ITO. A vision is to modify and chemically functionalize graphene to allow for better processing and to incorporate these novel materials into optoelectronic devices and sensors.

Organic-inorganic hybrids are another promising material class, combining inorganic nanoparticles with interesting fluorescent, absorbing and/or magnetic properties with conjugated polymers. Further, organic/inorganic hetero-layered stacks are promising for tandem solar cells, for memory devices, and/or for encapsulation purposes. 

Groups: Mathur | Meerholz | Loosdrecht