In der vorliegenden Dissertation werden numerische Verfahren zur Simulation von mikrofluidischen Systemen vorgestellt, welche mittels electrowetting-on-dielectrics (EWOD) aktuiert werden. Als Anwendungsbeispiel wird eine chipintegrierte nichtmechanische Mikropumpe präsentiert. Die Pumpwirkung wird durch…
This study presents a comprehensive and systematic investigation of the deposition and patterning of hydrogenated amorphous silicon carbide (a-SiC:H) using advanced plasma-based techniques to precisely tailor its optical characteristics for micro-optical applications. We demonstrate the ability to adjust…
Diese Arbeit trägt zum theoretischen Verständnis von Solarzellenmaterialien bei, die über dotiertes Silizium hinausgehen. Insbesondere werden Perowskite und III-V-Tandemsolarzellenmaterialien behandelt, wobei die Arbeit wie folgt gegliedert ist. Im ersten Teil nutzen wir die Dichtefunktionaltheorie um…
Predicting spectra and related properties such as the dielectric function of crystalline materials based on machine learning has a huge, hitherto unexplored, technological potential. For this reason, we create an ab initio database of 9915 dielectric tensors of semiconductors and insulators calculated…
Correct mesh handling and in particular domain extraction is an important step of many simulation workflows. In the boundary element method, for example, only the surfaces of arbitrarily shaped domains have to be meshed. Here, an algorithm is presented that extracts all distinct spatial regions and domains…
Multiabsorber structures for photoelectrochemical devices based on III–V semiconductor compounds enable direct solar-to-fuel conversion with the highest efficiencies to date as their tunable band gaps allow optimal exploitation of the solar spectrum. In monolithic tandem record devices, GaInP is frequently…
We systematically investigate the correlations between exciton binding energies and various easily calculated ground-state properties ("predictors") that have been proposed to correlate with them. We do so for 51 bulk compounds, ranging from simple binary semiconductors to more exotic materials such…
A robust, simple, and efficient convergence workflow for GW calculations in plane-wave-based codes is derived from more than 7000 GW calculations on a diverse dataset of 70 semiconducting and insulating solids divided into 60 bulk and 10 2D materials. The workflow can significantly accelerate material…
A microfluidic pump is presented that generates its pumping action via the EWOD (electrowetting-on-dielectric) effect. The flow is generated by the periodic movement of liquid-vapor interfaces in a large number (≈10⁶) of microcavities resulting in a volume change of approx. 0.5 pl per cavity per pump…
Cambridge: Royal Society of Chemistry (RSC), 2024-04-24
Artificial leaves could be the breakthrough technology to overcome the limitations of storage and mobility through the synthesis of chemical fuels from sunlight, which will be an essential component of a sustainable future energy system. However, the realization of efficient solar-driven artificial leaf…
Singularities in the fundamental solutions pose a mathematical challenge for all applications of the boundary element method, if the source and field point lie on the same element. To avoid complex and error-prone numerical procedures, analytical solutions for the integrals that arise are desirable.…
A fabrication strategy for high-efficiency passive three-dimensional microfluidic valves with no mechanical parts fabricated in silicon and glass substrates is presented. 3D diffuser-nozzle valve structures were produced and characterized in their added value in comparison to conventional diffuser-nozzle…
Nanosponges are subject of intensive research due to their unique morphology, which leads among other effects to electrodynamic field localization generating a strongly nonlinear optical response at hot spots and thus enable a variety of applications. Accurate predictions of physical properties require…
We present a highly efficient simulation method for the calculation of three-dimensional quasi-static interface shapes under the influence of electric fields. The method is especially useful for the simulation of microfluidic systems driven by electrowetting on dielectrics because it accounts automatically…
Melville, NY: American Inst. of Physics, 2022-12-12
Time‐resolved photoluminescence (TRPL) measurements and the extraction of meaningful parameters involve four key ingredients: a suitable sample such as a semiconductor double heterostructure, a state‐of‐the‐art measurement setup, a kinetic model appropriate for the description of the sample behavior,…
A multistage optimization method is developed yielding Tesla valves that are efficient even at low flow rates, characteristic, e.g., for almost all microfluidic systems, where passive valves have intrinsic advantages over active ones. We report on optimized structures that show a diodicity of up to 1.8…
The ASi-Sii defect model as one possible explanation for light-induced degradation (LID) in typically boron-doped silicon solar cells, detectors, and related systems is discussed and reviewed. Starting from the basic experiments which led to the ASi-Sii defect model, the ASi-Sii defect model (A: boron,…
We explore the atomic structures and electronic properties of the As-terminated GaAs(001) surface in the presence of hydrogen based on ab initio density functional theory. We calculate a phase diagram dependent on the chemical potentials of As and H, showing which surface reconstruction is the most stable…
The atomic structure and electronic properties of the InP and Al0.5In0.5P(001) surfaces at the initial stages of oxidation are investigated via density functional theory. Thereby, we focus on the mixed-dimer (2 × 4) surfaces stable for cation-rich preparation conditions. For InP, the top In-P dimer is…
Building nanoparticle (NP) superlattices formed in a complex fashion by subsets that can be explored separately presents a promising approach to realize the next generation of superlattices for different applications. Here, by incorporating self‐aligned and geometrically different subsets of Au NPs into…