Research

Today, we already use "organic electronics" in everyday life. Self-luminous displays in smartphones are a prominent example. Here, very thin layers of functional organic molecules are embedded between flat electrodes and are excited by an external voltage to emit visible light.

The Sokolowski laboratory investigates the fundamental chemical and physical processes that play a role when such organic molecules come into contact with electrode surfaces and how to exploit this knowledge for novel devices. These experiments aim at gaining a detailed understanding of the chemical interactions that occur between the electrode surface and the molecules. Here, the lab investigates model systems on a microscopic level. Methods as scanning tunneling microscopy (STM), low-energy electron diffraction (LEED) and techniques based on photoelectron spectroscopy, e.g., x-ray standing waves at normal incidence (NIXSW), provide detailed information about the geometric and electronic structure of molecules that are in contact with the surface of a solid material.

Another topic of interest concerns the arrangement and formation of condensed molecular layers on surfaces. There, one of the most fascinating questions concerns the crystalline structures of molecular layers on surfaces which form under the competition of intermolecular and interfacial bonds. A further topic are the fluorescence spectra of individual or condensed layers of molecules on surfaces. It turns out that these spectra contain rich information about the specific molecular bonds to the surface and the lateral ordering in the molecular phase. This plays an important  role for the resulting transition dipole of the layer and can be exploited to tailor the fluorescence properties of molecular layers.

In the past, the group has systematically compared the surfaces of noble metals for different surface orientations. Recently, the interest has shifted to surfaces of insulating materials, e.g., KCl, 2D materials (e.g., hexagonal boron nitride), and vicinal (i.e., stepped) surfaces. On surfaces of insulators the interfacial bonding interferes less with the electronic states of adsorbed (aromatic) organic molecules. Prototypical molecules (acenes, perylenes) are studied, but also specially designed molecules in close cooperation with synthetically oriented groups in organic chemistry.

This research is funded by the German Research Foundation (DFG), in particular within the DFG Research Training Group "Template Designed Organic Electronics (TiDE)".