In the semiconductor nanostructures work group, fundamental materials research comprises the conversion of light into other energy forms for photovoltaic and sensor applications and photo-driven hydrogen production. The materials used for this purpose are nanostructured in a targeted manner to obtain model systems for fundamental research and novel characteristics, in particular for the development of innovative application concepts.
The current focus of research includes the following topics, which are being processed both experimentally and with the help of theoretical models:
- Highly-ordered supramolecular chromophore structures for organic and hybrid solar cells and organic light-emitting diodes (OLEDs): The (molecularly-thin) thin films of organic chromophores can be assembled to model layer systems with a defined morphology and interfaces in order to carry out a detailed study of charge separation and transport at the interfaces. Furthermore, strongly directional optical properties can be implemented that can be used as non-Lambert emitters for OLEDs and in novel semi-transparent solar cells.
- Silicon nanostructures for photo-driven hydrogen production: Silicon-based nanostructures have a series of excellent physical and chemical properties that make them ideal for different applications, including photo-driven hydrogen production. In this group, fundamental aspects of hydrogen production based on silicon nanostructures, such as charge carrier transport, mechanisms of photocatalysis, and methods of nanostructuring, are researched and optimized.
- Molecular sensors for the detection of small molecules in the breath or surrounding air: Molecular sensor layers are developed using electronic noses to detect physiologically relevant molecules such as nitrogen or carbon oxides. These layers reversibly bind analytes, can be electronically or photonically read, and allow the development of inexpensive organic alternatives to classic electronic noses based on inorganic semiconductors.
- Inorganic semiconductor nanostructures for cancer theranostics: New approaches to the in vitro and in vivo visualization and biodegradation of silicon nanoparticles in cancer cells/tumors through linear and nonlinear optical imaging methods are being tested. The results show new prospects for multimodal visualization, in particular to determine the absorption and chemical composition of silicon nanoparticles and their distribution in tumor cells. These findings lay the foundation for the use of silicon nanoparticles as highly-efficient theranostic substances in personalized therapies.
Processes and Methods
In this work group, the following processes and characterization methods are applied:
- Production and structuring of thin (in)organic layers: Top-down and bottom-up technologies and thin-film technology (CVD, ALD, PVD), lithography, chemical methods for nanostructuring and surface modification, Langmuir-Blodgett (LB) and Langmuir-Schäfer technology (LB: standard and alternate depositions, temperature control, light-dark measurements, R2R integration), XRD, EBSD, EDX, electron and ion microscopy; SEM, TEM, FIB
- Spectroscopic methods: Standard absorption, emission (polarization and angle-dependent), and fluorescence excitation spectroscopy, online fluorescence monitoring of LB processes, photothermal deflection spectroscopy (PDS), external quantum efficiency (EQE) measurements, electroluminescence (EL), ellipsometry, and UV-Vis spectroscopy
- Molecular mechanical and quantum chemical simulations: Geometric optimization and conformer identification of large molecules, assessment of HLB values, calculation of absolute molecular orbital energy layers, absorption and emission spectra (with oscillation broadening), description of properties from molecular clusters to materials, and description of the photoexcitation dynamic (FMS, in cooperation with Prof. Martínez) and fluorescence lifetimes.