Research

Research in our group is located somewhere between basic research and technology development with a focus on the synthesis of Photonic Nanostructures for various applications in the areas of opto-, nano- and large area electronics, optical and electrical sensing as well as nano-photonics. To cover these diverse topics our research group is devided into several subgroups, as listed below:

Photovoltaics: Nowadays, photovoltaics is one of the major sources of renewable electricity. The goal of the photovoltaics subgroup is the implementation of photonic and plasmonic nano-scatterers in PV devices to enhance and control light absorption especially in thin film solar cells. Novel types of materials interfaces like hybrid organic-inorganic and semiconductor-insulator-semiconductor heterojunctions are investigated for an efficient charge carrier collection especially over large surfaces in three dimensional nano-architectures. Cost efficient and materials saving transparent conductive device contacts are developed by combining metal nanoparticles and graphene with atomic layer deposition of metal oxides.

Electron Microscopy & Analysis: We accumulate a multitude of analytical and modifying techniques from the fields of scanning electron microscopy, focused ion beam systems and Raman spectroscopy. An important task is to correlate several of those techniques to enable a deeper understanding of nanostructured materials. Therefore, the EMA subgroup supports all other subgroups and several divisions of the MPL with its extensive knowledge and equipment.

Nano Optics: Structural geometries of particles and materials with sizes in the visible wavelength regime can control the propagation of light in unprecedented ways. Especially, metallic nanostructures provide for extreme light localization, for efficient scattering and, in combination with dielectric counterparts, for extremely high local densities of electromagnetic states. Such phenomena are investigated and applied by the fabrication and optimization of nano-architectures for the use as metamaterials (of chiral or hyperbolic nature for spectrally matched molecule coupling), optical antennas (e.g. for tip enhanced Raman spectroscopy ) and efficient scatterers (e.g. for enhanced solar cell absorption). To gain a fundamental understanding of the underlying physical principles numerical and analytical approaches in electrodynamics are employed.

GaN & Graphene: Growth of group-III-nitrides such as GaN, InGaN and AlGaN is carried out in a metal-organic vapour phase epitaxy (MOVPE) system. We focus on the realization of nanowires for optoelectronic applications in photovoltaic and light emitting devices. Bottom-up GaN nanowires are grown by a self-catalyzed vapor-liquid-solid growth whereas top-down nanowires are etched from a GaN layer by nanosphere lithography and reactive ion etching. The n-type GaN nanowires are overgrown with InGaN quantum wells and p-type GaN to complete the device structure. As a novel contact material graphene is investigated either in the bottom-up or the top-down approach.

Solar Fuels: Conversion of solar energy into chemical energy is gaining considerable attention in the renewable energy production sector. Since sunlight and water are almost inexhaustible sources, it is attractive to split water directly into hydrogen and oxygen using solar energy. Hydrogen, as a chemical fuel, is a convenient and portable energy source. The goal of our research is to develop 3D nano-architectures as cost effective and efficient photo-anodes and photo-cathodes for water splitting.

 

 

 

For more details on the group activities you may also refer to our publications.