arXiv subjects

Maximilian Krause

Publications and source records attributed to Maximilian Krause.

3 recordsLinked to original sources

arXiv2026

Loss analysis of Low Bandgap (Ag,Cu)(In,Ga)Se2 Solar Cells for Tandem Applications

Tandem solar cells can better harness the energy of the solar spectrum. Chalcopyrite solar cells have drawn attention, being the only highly efficient devices with bandgap around 1.0 eV, suitable for bottom cells. In the quest for better efficiencies, we conduct a complete loss analysis of 1.0 eV bandgap (Ag,Cu)(In,Ga)Se2 cells with efficiencies around 18.5%. We perform absolute photoluminescence, electroluminescence, JV and EQE measurements on the absorber and the finished cells to analyze losses of short-circuit current, open-circuit voltage and fill factor. The relevant losses in current are due to absorption losses in the absorber and could only be mitigated by light management structures. But the most significant losses are found in the voltage, due to non-radiative recombination in the absorber, and the fill factor, due to a high diode factor. The diode factor of the cells is significantly higher than in the absorber alone, indicating a strong influence of recombination in the space charge region.

cond-mat.mtrl-sci↗

arXiv2025

Diffraction Stress Factors Calculated Using a Maximum Entropy Method

Diffraction-based stress analysis of textured materials depends on understanding their elastic heterogeneity and its influence on microscopic strain distributions, which is generally done by using simplifying assumptions for crystallite interactions to calculate tensorial stress factors or in the case of very strong textures, by considering the material phase as a single crystal (crystallite group method). In this paper, we apply the micromechanical Maximum Entropy Method (MEM) to this purpose, which marks its first use for materials with texture. The special feature of this approach is a native parametrization by the effective stiffness of the material, which allows the approach to be tailored to a macroscopically measurable sample property. We perform example stress analyses of cold-rolled copper, finding through validation with full-field simulations that the MEM yields accurate local strains even for materials with extremely sharp textures. In an example stress analysis of mildly textured cold-rolled ferritic steel, the accuracy of the approach compares favorably to the established Voigt, Reuss and self-consistent Eshelby-Kröner approaches. Compared to the latter, the method is also numerically efficient to calculate.

cond-mat.mtrl-sci↗

arXiv2022

FFT-based investigation of the shear stress distribution in face-centered cubic polycrystals

The onset of nonlinear effects in metals, such as plasticity and damage, is strongly influenced by the heterogeneous stress distribution at the grain level. This work is devoted to studying the local stress distribution of shear stresses resolved in the slip systems as the critical driving force for plastic deformations. Specific grain orientations with respect to load direction are investigated in the linear elastic regime and at incipient plastic deformations based on a large ensemble of microstructures. The elastic anisotropy of the single crystal is found to have a crucial influence on the scatter of the stress distribution, whereas the Young's modulus in the respective crystal direction governs the mean stress in the grain. It is further demonstrated that, for higher anisotropy, the shear stresses deviate from the normal distribution and are better approximated by a log-normal fit. Comparing the full-field simulations to the Maximum Entropy Method (MEM), reveals that the MEM provides an excellent prediction up to the second statistical moment in the linear elastic range. In a study on the spatial distribution of shear stresses, the grain boundary is identified as a region of pronounced stress fluctuations and as the starting point of yielding during the elastic-plastic transition.

cond-mat.mtrl-sci↗