Recent improvements in light-emitting diode (LED) technology has allowed for the use of LEDs for solar simulators with excellent characteristics. In this paper, we present a solar simulator prototype fully based on LEDs. Our prototype has been designed specifically for light soaking and current-voltage (I(V )) measurements of amorphous silicon solar cells. With 11 different LED types, the spectrum from 400 to 750 nm can be adapted to any reference spectrum-such as AM1.5g-with a spectral match corresponding to class A+ or better. The densely packed LEDs provide power densities equivalent to 4 suns for AM1.5g or 5 suns with all LEDs at full power with no concentrator optics. The concept of modular LED blocks and electronics guarantees good uniformity and easy up-scalability. Instead of cost-intensive LED drivers, lowcost power supplies were used with current control, including a feedback loop on in-house developed electronics. This prototype satisfies the highest classifications (better than AAA from 400 to 750 nm) with an illuminated area of 18 cm × 18 cm. For a broader spectrum, the spectral range could be extended by using other types of LEDs or by adding halogen lamps. The space required for this can be saved by using LEDs with higher power or by reducing the maximum light intensity.

An electrospray microchip for mass spectrometry comprising an integrated passive mixer to carry out on-chip chemical derivatizations is described. The microchip fabricated using UV-photoablation is composed of two microchannels linked together by a liquid junction. Downstream of this liquid junction, a mixing unit made of parallel oblique grooves is integrated to the microchannel in order to create flow perturbations. Several mixer designs are evaluated. The mixer efficiency is investigated both by fluorescence study and mass spectrometric monitoring of the tagging reaction of cysteinyl peptides with 1,4-benzoquinone. The comparisons with a microchip without a mixing unit and a kinetic model are used to assess the efficiency of the mixer showing tagging kinetics close to that of bulk reactions in an ideally mixed reactor. As an ultimate application, the electrospray micromixer is implemented in a LC-MS workflow. Online derivatization of albumin tryptic peptides after a reversed-phase separation and counting of their cysteines drastically enhance the protein identification.Mass spectrometry (MS) based workflows play a major role in proteomics, 1,2 to identify, characterize, and quantify proteins at an ever increasing throughput, and in ever more complex mixtures. A number of approaches have been investigated to complement the mass spectrometric analysis of tryptic peptides based on chemical tagging, in order to isolate specific subclasses of proteins by affinity baits, or for quantitation purposes. Furthermore, the use of nonquantitative addition of chemical probes to increase the information content of MS analysis is a promising approach. For example, Sechi and Chait proposed the differential alkylation of cysteine residues as a way to increase the identification score in peptide mass fingerprinting. 3 Over the last years, our lab has been involved in the study of benzoquinone reagents as specific tags for cysteine residues in acidic solution. More particularly, a novel methodology based on the on-chip electrochemical tagging of cysteines, by oxidation of hydroquinone into benzoquinone at the microchip electrode, during ESI-MS of peptides has been introduced. 4 The potential of this on-line electrochemical tagging was demonstrated with microfabricated electrospray emitters, where instrumental parameters (current density at the electrospray electrode, residence time of analytes and chemical probes, etc.) can be properly tailored and controlled. However, this methodology was so far limited to off-line analysis of peptide fractions. In order to bring the potential of tagging methodologies to on-line analysis (e.g., in HPLC-ESI-MS analysis of tryptic peptides), we have developed here a combined derivatization/electrospray device where we physically mix the samples with the labeling reagent.A number of studies have been performed to study chemical reaction kinetics by ESI-MS, pioneered by Lee et al. 5 In their setup, reactants were mixed manually in a vessel that was directly coupled to the ESI source. The time sca...

The drift length L drift = μτE within the i layer of a-Si:H solar cells is a crucial parameter for charge collection and efficiency. It is strongly reduced not only by light-induced reduction of μτ, but also by electric field deformation ΔE by charges near the p-i and i-n interfaces. Here, a simple model is presented to estimate contributions of free carriers, charges trapped in band tails and charged dangling bonds to ΔE. It is shown that the model reproduces correctly trends observed experimentally and by ASA simulations: charged dangling bonds contribute most to ΔE of meta-stable cells. Electrons trapped in the conduction band tail near the i-n interface lead to the strongest field deformation in the initial state, while positively charged dangling bonds near the p-i interface get more important with degradation under AM1.5g spectrum. The measurable parameter V coll is proposed as an indirect parameter to estimate the electric field, and an experimental technique is presented that could enable the distinction of defects near the p-i and the i-n interfaces.

This paper describes the different aspects of the design of rapid and sensitive immunoassays in a microchip platform, with accurate control of the fluidics inside the microchannels. In order to get the required sensitivity and reproducibility, it is notably necessary to monitor and actively control the fluidic events at each step of the assay. Particularly, it is important to know at what linear velocity the liquid is transported through the microfluidic reactor, and we will show here how individual flow sensors inserted in each channel of the disposable chip can be used to precisely monitor the fluid flows within microchannels, and this with various fluid delivery means.

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