Molecule puzzles

FAU researchers examine how molecules arrange themselves on surfaces used in new technologies

It is a little like throwing pieces of a puzzle at a magnetic board and hoping they will fall into place by themselves. This is roughly what scientists do when they apply molecules to surfaces in order to create materials for new technologies such as organic solar cells. So far, they lack the knowledge to place the molecules on the surfaces in a controlled manner. A research group recently founded at FAU, funCOS, aims to provide that knowledge. The German Research Foundation (DFG) has now given the green light to the team of scientists led by Prof. Dr. Jörg Libuda, Chair of Chemistry and Pharmacy.

Scientists have modelled organic solar cells or electronic components on nature where molecules have important functions: porphyrins, for instance, absorb the sunlight during photosynthesis in plants, converting the energy and passing it on. Porphyrins are now to do the same thing in organic solar cells.

For power to be generated, however, the molecules need to be applied to carrier surfaces. The scientists place the molecules in a solvent, immerse the carrier in the solution – ‘and then you hope for as many molecules as possible to cling to the surface in an orderly manner,’ explains the speaker of funCOS, Prof. Jörg Libuda. So far, scientists still depend on serendipity: how many molecules are bound to the surface, what chemical bonds they form and which chemical reactions they trigger – the researchers can control none of these things so far. The order of the molecules is of vital importance if technologies such as our example of organic solar cells are to function: if they are placed on the surface in the wrong position or irregularly, malfunctions ensue.

This is where the research group FOR 1878 ‘funCOS – Functional Molecular Structures on Complex Oxide Surfaces’ comes into play: 15 research groups at FAU are already examining the areas where molecules and carrier surfaces meet, which are known as molecule/oxide interfaces. ‘We want to gain control of the molecules in order to get access to certain functions, such as collecting sunlight,’ Libuda summarises the project. The research results are to be compiled in a type of modular system, allowing researchers to create bespoke, functional molecule/oxide interfaces.

An ambitious endeavour: the scientists have to test the molecules on various surfaces and then examine them with regard to different properties. To ensure ideal test conditions, the researchers are using simplified models. ‘We have to be able to control the experimental set-up right down to the smallest atom. This is why we only use surfaces where we know the exact location of every atom,’ Libuda explains the researchers’ approach. The scientists from the Faculty of Sciences and the Faculty of Engineering are not only researching different molecules and carrier surfaces, they are also examining various aspects of their properties. ‘If you look through a microscope, you see the molecule as a little bump. The location of the molecule on the surface may be clearly visible, but the microscope does not tell you anything about chemical bonds. Another group is then tasked with that part,’ Libuda explains.

Further information:

Prof. Dr. Jörg Libuda
Phone: +49 (0)9131 85 27308