Chemical fluctuations in polycrystalline thin-films for photovoltaic devices
Within this project we investigate chemical fluctuations at the nanometre scale in polycrystalline Cu(In,Ga)Se2 and CuInS2 thin-flims used as absorber material in solar cells.
Secondary phase formation as well as chemical fluctuations such as impurity segregation at structural defects like grain boundaries can significantly affect the optoelectronical properties of photovoltaic materials. Within this project we investigate such chemical fluctuations at the nanometre scale in polycrystalline Cu(In,Ga)Se2 and CuInS2 thin-flims used as absorber material in solar cells. We apply combined scanning transmission electron microscopy (STEM) with energy dispersive X-ray spectroscopy (EDX) as well as correlated transmission Kikuchi diffraction (TKD) and atom probe tomography (APT).
Accumulation and diffusion of Na (green) along Cu depleted structural defects (blue) in epitaxial grown CuInSe2 films on GaAs substrate
Mechanistic description of In/Ga interdiffusion. STEM-BF image of a cross section from a Na2Se treated CuInSe2 film grown on GaAs substrate and corresponding Ga, In and Cu elemental maps.
Mechanistic description of In/Ga interdiffusion. STEM-BF image of a cross section from a Na2Se treated CuInSe2 film grown on GaAs substrate and corresponding Ga, In and Cu elemental maps.
Image quality maps from a TKD measurement of an APT needle and corresponding unique color map showing a RHAGB (blue) and ∑3 TB (red). Na & C co-segregation as well as Cu enrichment (blue iso-concentration surface) at the RHAGB. Concentration profile across the RHAGB revealing an atomic redistribution.
Image quality maps from a TKD measurement of an APT needle and corresponding unique color map showing a RHAGB (blue) and ∑3 TB (red). Na & C co-segregation as well as Cu enrichment (blue iso-concentration surface) at the RHAGB. Concentration profile across the RHAGB revealing an atomic redistribution.
International researcher team presents a novel microstructure design strategy for lean medium-manganese steels with optimized properties in the journal Science
Here the focus lies on investigating the temperature dependent fracture of materials down to the individual microstructural length-scales, such as respective phases, grain/phase boundaries or hetero-interfaces, to understand brittle-ductile transitions in deformation and the role of chemistry or crystallography on it.
This project is part of Correlative atomic structural and compositional investigations on Co and CoNi-based superalloys as a part of SFB/Transregio 103 project “Superalloy Single Crystals”. This project deals with the identifying the local atomic diffusional mechanisms occurring during creep of new Co and Co/Ni based superalloys by correlative…
The aim of the work is to develop instrumentation, methodology and protocols to extract the dynamic strength and hardness of micro-/nano- scale materials at high strain rates using an in situ nanomechanical tester capable of indentation up to constant strain rates of up to 100000 s−1.
In this project, we investigate a high angle grain boundary in elemental copper on the atomic scale which shows an alternating pattern of two different grain boundary phases. This work provides unprecedented views into the intrinsic mechanisms of GB phase transitions in simple elemental metals and opens entirely novel possibilities to kinetically engineer interfacial properties.
