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For the fabrication of silicon heterojunction (SHJ) solar cells, hydrogenated amorphous silicon (a-Si:H) layers are deposited on each side of textured c-Si wafers. The high conversion efficiency of these cells relies significantly on the excellent surface passivation provided by these layers. A perfectly clean surface, free from organic and metallic impurities, is therefore a very important aspect in the fabrication of SHJ cells. Moreover, also for future heterojunction structures, using for example metal oxides in passivating contacts, a good control of surface quality will be important. In this work, the wet-chemical cleaning steps after KOH random pyramid texturing are investigated. The current cleaning process at ECN, based on procedures described in literature, takes about 90 min and includes many steps. This is very elaborative and costly and forms a barrier for industrial acceptance of the process. The aim of this work is to simplify the cleaning process, while maintaining good surface passivation and therefore high solar cell efficiency. By systematic testing of different sequences and process times of wet-chemical oxidation and etching steps, we arrived at a good qualitative understanding of their purposes and interactions. Optimization resulted in a wet-chemical cleaning sequence that takes less than 30 min and results in high minority carrier lifetime values that are similar to the reference procedure.

In the past years a wide discussion has been held among asphalt researchers regarding the existence and interpretation of observed microstructures on bitumen surfaces. To investigate this, the RILEM technical committee on nano bituminous materials 231-NBM has conducted a round robin study combining differential scanning calorimetry (DSC) and Atomic Force Microscopy (AFM). From this, methods for performing DSC and AFM tests on bitumen samples and determination of the influence of wax on the observed phases, taking into account thermal history, sample preparation and annealing procedure, are presented and critically discussed. DSC is used to measure various properties and phenomena that indicate physical changes such as glass transition temperature (T g) and phase transition such as melting and crystallization. In the case of existence of wax, either natural or synthetic, it can further indicate the melting point of wax, that could be used to determine wax content. The results from seven laboratories show that T g temperatures obtained from the heating scans are more repeatable and easier to obtain in comparison to the cooling scans. No significant difference was noted for T g's obtained from the first and second heating scans. AFM is an imaging tool used to characterize the microstructures on a bituminous surface. Using AFM three phases in the materials with wax could be distinguished. The changes in the phases observed with AFM for increases in temperature were correlated with the DSC curve, and it could be established that the so called "Bee" structure disappeared around the melting peak in the DSC curve. Thus, this research has confirmed the relation between the microstructures on a bitumen surface and the wax content. cop. 2013 RILEM.

A reversed-phase liquid chromatography-linear ion trap-Fourier transform ion cyclotron resonance-mass spectrometry method was developed for the profiling of lipids in human and mouse plasma. With the use of a fused-core C₈ column and a binary gradient, more than 160 lipids belonging to eight different classes were detected in a single LC-MS run. The method was fully validated and the analytical characteristics such as linearity (R², 0.994-1.000), limit of detection (0.08-1.28 μ/mL plasma), repeatability (RSD, 2.7-7.9%) and intermediate precision (RSD, 2.7-15.6%) were satisfactory-The method was successfully applied to p53 mutant mice plasma for studying some phenotypic effects of p53 expression. © 2008 American Chemical Society.