Extracting accurate capacitance voltage curves from impedance spectroscopy

We propose a method to obtain accurate capacitance-voltage (C-V) curves in the presence of multiple space charges. This method uses impedance spectroscopy to evaluate individual space charges separately. The advantage is that the knowledge of the exact equivalent circuit is not essentially needed. The comparison with other methods to calculate the doping concentration NA shows that our method is unaffected by series resistances and agrees best with the correct value of NA. The evaluation of the impedance spectra leads to a more thorough understanding of the respective Mott-Schottky plots

Laser Processed Black Silicon for Photovoltaic Applications

We present a femtosecond laser pulse process that induces a texture-like surface structure on silicon wafers and optionally incorporates sulfur into the silicon lattice for emitter formation depending on the processing atmosphere. Such laser processed Black Silicon provides an easily adjustable surface roughness for good light trapping in silicon solar cells. The structure is independent of the silicon crystal orientation and is easily applied on one wafer side only. A sulfur emitter can be formed within the laser structuring process, and allows electric current extraction from a solar cell structure manufactured from this material. Then the advantage is that no further emitter formation step like diffusion is necessary compared to other Black Silicon solar cell approaches, where the Black silicon is created wet chemically. By incorporating sulfur in the silicon crystal lattice, we can show that this Black Silicon absorbs in the infrared wavelength regime. This characteristic can potentially be used to better exploit the energy in the sun spectrum. We manufacture a laser processed Black Silicon solar cell prototype without any emitter diffusion step and achieve the highest efficiency of 4.5 % reported for this cell type

Tandem solar cell concept using Black Silicon for enhanced infrared absorption

In this work we present a novel tandem solar cell concept that is based on enhanced below band gap infrared absorption. The solar cell structure is based on silicon and infrared activated Black Silicon. Infrared active Black Silicon is produced by exposing silicon to fs-laser pulses. It features an enhanced IR absorption, when processed under a sulfur-containing atmosphere. Then sulfur is incorporated into the silicon lattice during laser processing providing energy states in the band gap. This silicon based tandem cell thus absorbs light with wavelengths beyond 1.1 μm. This can potentially increase the overall efficiency. In this paper we present the first experimental realization of this concept. We use a standard aluminium-back-surface-field (Al-BSF) silicon solar cell and implement a Black Silicon solar cell on its rear side for enhanced IR absorption. Current and voltage measurements show the feasibility of our concept

Focal adhesion kinase plays a dual role in TRAIL resistance and metastatic outgrowth of malignant melanoma

Despite remarkable advances in therapeutic interventions, malignant melanoma (MM) remains a life-threating disease. Following high initial response rates to targeted kinase-inhibition metastases quickly acquire resistance and present with enhanced tumor progression and invasion, demanding alternative treatment options. We show 2nd generation hexameric TRAIL-receptor-agonist IZI1551 (IZI) to effectively induce apoptosis in MM cells irrespective of the intrinsic BRAF/NRAS mutation status. Conditioning to the EC50 dose of IZI converted the phenotype of IZI-sensitive parental MM cells into a fast proliferating and invasive, IZI-resistant metastasis. Mechanistically, we identified focal adhesion kinase (FAK) to play a dual role in phenotype-switching. In the cytosol, activated FAK triggers survival pathways in a PI3K- and MAPK-dependent manner. In the nucleus, the FERM domain of FAK prevents activation of wtp53, as being expressed in the majority of MM, and consequently intrinsic apoptosis. Caspase-8-mediated cleavage of FAK as well as FAK knockdown, and pharmacological inhibition, respectively, reverted the metastatic phenotype-switch and restored IZI responsiveness. FAK inhibition also re-sensitized MM cells isolated from patient metastasis that had relapsed from targeted kinase inhibition to cell death, irrespective of the intrinsic BRAF/NRAS mutation status. Hence, FAK-inhibition alone or in combination with 2nd generation TRAIL-receptor agonists may be recommended for treatment of initially resistant and relapsed MM, respectively

Experimental implementation of a silicon wafer tandem solar cell

We combine aluminum back surface field (Al-BSF) solar cell precursors with an additional rear side infrared active floating emitter in a tandem cell configuration. This emitter is implemented area selectively by fs-laser hyperdoping in a sulfurous atmosphere. Its design as a floating emitter conceals losses induced by the laser process as long as n-doping occurs. All processes are adapted and supplemented by just a single new process step

Antibody engineering

xii, 790 p. : ill. ; 25 cm