A fluorescence-based device was developed for immunosuppressants. A measuring chip with ten parallel microchannels allows the simultaneous detection of more than one analyte with replicate measurements. The device is equipped with a microfluidic circuitry, which handles the sample mixing with necessary chemicals using an additional chip and its pumping into the measuring chip, and with integrated thin-film amorphous silicon photodiodes for the fluorescence detection. Submicrometric fluorescent magnetic particles are used to improve the efficiency of the assay. Results on the measurements of mycophenolic acid and cyclosporine A in both spiked solutions and microdialysate samples from patient blood are reported.

Single-color reflectrometry is a sensitive and robust detection method in optical biosensor applications, for example for bioanalysis. It is based on the interference of reflected monochromatic radiation and is label free. We present a novel setup for single-color reflectometry based on the patented technology of Berner et al. from 2016. Tilting areas of micro-mirrors allow us to encode the optical reflection signal of an analyte and reference channel into a particular carrier frequency with the amplitude being proportional to the local reflection. Therefore, a single photodiode is sufficient to collect the signals from both channels simultaneously. A 180∘ phase shift in the tilt frequency of two calibrated micro-mirror areas leads to a superposition of the analyte and reference signal which enables an efficient reduction of the baseline offset and potential baseline offset drift. A performance test reveals that we are able to detect changes of the refractive index n down to Δn < 0.01 of saline solutions as regents. A further test validates the detection of heterogeneous binding interaction. This test compromises immobilized testosterone-bovine serum albumin on a three-dimensional layer of biopolymer as ligand and monoclonal anti-testosterone antibodies as analyte. Antibody/antigen binding induces a local growth of the biolayer and change in the refractive index, which is measured via the local change of the reflection. Reproducible measurements enable for the analysis of the binding kinetics by determining the affinity constant KA = 1.59 × 10− 7 M− 1. In summary, this work shows that the concept of differential Fourier spotting as novel setup for single-color reflectometry is suitable for reliable bioanalysis.

The present paper describes a compact point of care (POC) optical device for therapeutic drug monitoring (TDM). The core of the device is a disposable plastic chip where an immunoassay for the determination of immunosuppressants takes place. The chip is designed in order to have ten parallel microchannels allowing the simultaneous detection of more than one analyte with replicate measurements. The device is equipped with a microfluidic system, which provides sample mixing with the necessary chemicals and pumping samples, reagents and buffers into the measurement chip, and with integrated thin film amorphous silicon photodiodes for the fluorescence detection. Submicrometric fluorescent magnetic particles are used as support in the immunoassay in order to improve the efficiency of the assay. In particular, the magnetic feature is used to concentrate the antibody onto the sensing layer leading to a much faster implementation of the assay, while the fluorescent feature is used to increase the optical signal leading to a larger optical dynamic change and consequently a better sensitivity and a lower limit of detection. The design and development of the whole integrated optical device are here illustrated. In addition, detection of mycophenolic acid and cyclosporine A in spiked solutions and in microdialysate samples from patient blood with the implemented device are reported.

Detailed structural investigations have been performed on a-Si1−xGex:H in 0 ≤ x ≤ l namely Raman, X-ray Photoelectron, and Photothermal Deflection Spectroscopies, which reveal the silicon sub-matrix to be considerably more rigid than the germanium one. In Si-Ge dominated networks distinct deviations from an overall random distribution of Si and Ge atoms can be deduced from a semi-quantitative analysis of the Raman data.

A main challenge towards ensuring improved lifetime performance and reduction of financial risks of photovoltaic (PV) technologies remains the accurate degradation quantification of field systems and the dependency of this performance loss rate to climatic conditions. The purpose of this study is to address these technological issues by presenting a unified methodology for accurately calculating the degradation rate (RD) of PV systems and provide evidence that degradation mechanisms are location dependent. The method followed included the application of data inference and time series analytics, in the scope of comparing the long-term RD of different crystalline Silicon (c-Si) PV systems, installed at different climatic locations. The application of data quality and filtering steps ensured data fidelity for the RD analysis. The yearly RD results demonstrated that the adopted time series analytical techniques converged after 7 years and were in close agreement to the degradation results obtained from indoor standardized procedures. Finally, the initial hypothesis that the RD is location dependent was verified, since the multicrystalline silicon (multi-c-Si) systems at the warm climatic region exhibited higher degradation compared to the respective systems at the moderate climate. For the investigated monocrystalline silicon (mono-c-Si) systems the location-dependency is also affected by the manufacturing technology.

Electroluminescence (EL) is a powerful tool for the qualitative mapping of the electronic properties of solar modules, where electronic and electrical defects are easily detected. However, a direct quantitative prediction of electrical module performance purely based on electroluminescence images has yet to be accomplished. Our novel approach, called “EL power prediction of modules” (ELMO) as presented here, used just two electroluminescence images to predict the electrical loss of mechanically damaged modules when compared to their original (data sheet) power. First, using this method, two EL images taken at different excitation currents were converted into locally resolved (relative) series resistance images. From the known, total applied voltage to the module, we were then able to calculate absolute series resistance values and the real distribution of voltages and currents. Then, we reconstructed the complete current/voltage curve of the damaged module. We experimentally validated and confirmed the simulation model via the characterization of a commercially available photovoltaic module containing 60 multicrystalline silicon cells, which were mechanically damaged by hail. Deviation between the directly measured and predicted current/voltage curve was less than 4.3% at the maximum power point. For multiple modules of the same type, the level of error dropped below 1% by calibrating the simulation. We approximated the ideality factor from a module with a known current/voltage curve and then expand the application to modules of the same type. In addition to yielding series resistance mapping, our new ELMO method was also capable of yielding parallel resistance mapping. We analyzed the electrical properties of a commercially available module, containing 72 monocrystalline high-efficiency back contact solar cells, which suffered from potential induced degradation. For this module, we predicted electrical performance with an accuracy of better than 1% at the maximum power point.

This study presents the first laser porosificated silicon anode for lithium‐ion batteries. The pulsed laser induced pore creation improves the cycling stability of the d = 210 nm thick sputtered thin film anodes compared to plain Si. Galvanostatic cycling with a charge capacity limited to C = 932 mAh g −1 and a 2 C current rate shows a stable cycling for more than N = 600 cycles. After N = 3000 cycles the laser porosificated and crystallized Si has a remaining capacity of C 3000 > 120 mAh g −1 . Postmortem scanning electron microscopy images after N = 3000 cycles prove that the laser porosification reduces cracks in the active layer.

Point-of-care testing (POCT) devices for continuous low-cost monitoring of critical patient parameters require miniaturized and integrated setups for performing quick high-sensitivity analyses, away from central clinical laboratories. This work presents a novel and promising laser-induced fluorescence platform for measurements in direct optical test formats that leads towards such powerful POCT devices based on fluorescence-labeled immunoassays. Ultimate sensitivity of thin film photodetectors, integrated with microfluidics, and a comprehensive optimization of all system components aim at low-level signal detection in the targeted biosensor application. The setup acquires fluorescence signals from the volume of a microfluidic channel. An innovative sandwiching process forms a flow channel in the microfluidic chips by embedding laser-cut double-sided adhesive tapes. The custom fit of amorphous silicon based photodiode arrays to the geometry of the flow channel enables miniaturization, fully adequate for POCT devices. A free-beam laser excitation with line focus provides excellent alignment stability, allows for easy and reliable swapping of the disposable microfluidic chips, and therewith greatly improves the ease of use of the resulting integrated device. As a proof-of-concept of this novel in-volume measurement approach, the limit of detection for the dye DY636-COOH in pure water as a model fluorophore is examined and found to be 26 nmol l(-1).

A novel therapeutic drug monitoring point of care testing (POCT) optical device for the detection of immunosuppressants in transplanted patients was designed and tested, with the body interface constituted by an intravascular microdialysis catheter (MicroEye®) which provides the dialysate as clinical sample. An optical biochip with 10 microchannels, based on total internal reflection fluorescence (TIRF), enables the frequent measurement of immunosuppressants. Heterogeneous competitive immunoassays for the detection of mycophenolic acid, tacrolimus and cyclosporine A are implemented on the different microchannels, with the derivative of the immunosuppressants immobilised on the bottom part of the micro-channels.

Fluorescence spectroscopy is a highly sensitive detection method widely used in analytical chemistry, bioanalytics, and medicine. The here presented amorphous silicon (a‐Si:H) based thin film photodetector arrays contribute to the miniaturization of this measurement method and thereby enable integration of a point‐of‐care testing (POCT) device. Revealed from photocurrent decay measurements, the limit of detection of the photodiodes with an active area A = 36.3 mm2 is in the 100 fA‐range. Dark current analysis at zero bias voltage yields a standard deviation σ = 4.4 fA for the thermally generated noise of the nip photodiodes. In the context of the desired application, a minimum detectable fluorescence radiation intensity Umin = 4.5 pW cm−2 with a dynamic range DNR = 78 dB is estimated. At the emission peak wavelength λem = 667 nm and with a bandwidth Δf = 0.25 Hz the photodiodes reach a noise equivalent power NEP = 54.6 fW Hz−1/2 and therewith a specific detectivity D* = 1.1 × 1013 Jones. Fluorescence measurements with the dye DY‐636 diluted in pure water with a molar concentration c = 1.31 μM demonstrate the suitability of the multi‐channel photodetectors for high‐sensitivity fluorescence spectroscopy.Low‐signal a‐Si:H photodetector multi‐channel chips in different geometrical layouts with an active area of up to 36.3 mm2 per diode.

We present a new and simple laser-based process to porosify thin film silicon using a pulsed laser. During deposition, we incorporate gas atoms or molecules into the Si thin film. Pulsed laser radiation of wavelength λ = 532 nm heats up thin film Si beyond its melting point. Upon heating, gas atoms or molecules form nm-sized thermally expanding gas bubbles in the silicon melt, until they explosively exit the film, leaving pores behind. Rapid heating and fast cooling during pulsed laser processing enable re-solidification of the liquid Si before the created pores contract and pore closure occurs within the liquid phase. Optimized plasma-enhanced chemical vapor deposition or sputtering of amorphous Si thin films on stainless steel substrate incorporates the necessary concentration of gas atoms or molecules. We are able to tailor the pore size between 50 and 550 nm by changing laser pulse energy density and film deposition parameters. Evaporated silicon containing no gas atoms forms only a few very large μ m-sized gas bubbles due to laser-induced vapor formation of evaporated solid material at the substrate–silicon interface.

In this work, the seasonality and performance loss rates of eleven grid-connected photovoltaic (PV) systems of different technologies were evaluated through seasonal adjustment. The classical seasonal decomposition (CSD) and X-12-ARIMA statistical techniques were applied on monthly DC performance ratio, RP, time series, constructed from field measurements over the systems' first five years of operation. The results have shown that the RP of crystalline silicon (c-Si) technologies was higher during winter. This was also the case for the copper–indium gallium-diselenide (CIGS) and cadmium telluride (CdTe) technologies but with lower seasonal amplitude. The amorphous silicon (a-Si) technology exhibited a different seasonal profile, with high RP during summer and autumn and low during winter. In addition, the trends extracted from the application of CSD and X-12-ARIMA on three-year, four-year and five-year RP time series were used to estimate linear performance loss rates. A comparison between standard linear regression (LR), CSD and X-12-ARIMA has shown that CSD and X-12-ARIMA resulted in higher rates overall for c-Si, 1.07 and 0.93%/year respectively, but with significantly less uncertainty than LR. Lastly, it was shown that X-12-ARIMA provided statistical inference in the presence of outliers and produced model residuals that were uncorrelated, in contrast to CSD.

The R & D status of cells and modules based on hydrogenated amorphous silicon (a-Si:H) and those based on CdTe and CuInSe2 is reviewed.The stability of a-Si:H solar cells is still a major concern, Improvements have been achieved on air empirical basis by application of multijunction structures, optimization of interfaces, etc, Stabilized efficiencies of close to 10 % have been reported. In parallel, the introduction of the 'defect-pool model' led to remarkable progress in understanding; it follows that a-SiGe:H instead of a-Si:H should be used for the i-layer (absorber). Improved cell engineering concepts, however, such as enhancement of the built-in electric field via reduction of the i-layer thickness and/or folded structures, are believed to be more promising.Polycrystalline thin-film cells based on CdTe and CuInSe2 ave not affected by inherent degradation mechanisms, The specific properties of these materials demand heterojunctions, and particular problems arise due to the polycrystallinity of the films and to the lattice mismatch and mismatch of the electronic band structures of the materials involved. These are discussed in conjunction with measures currently applied for optimizing solar cell performance. Both cell types exhibit efficiencies in the range 16-17 %.Estimations of, production costs and energy payback times of thin-film photovoltaic modules are reviewed (even below 1 US$ W-p(-1) and as low as 4 months, respectively) and environmental concerns, especially for Cd-containing cells, are summarized.

The effects of current mismatch and shading on the power output of single photovoltaic (PV) modules are well analyzed, but only few investigations address mismatch losses at a PV system level that also limit the annual energy yield. The simple question, what happens if PV strings with different numbers of modules are connected in parallel, has not yet been discussed in detail. In case of strings with unequal module count, the system builder must decide whether to use inverters with multiple maximum power point (MPP) trackers, module-power optimizers, or to shorten all strings for balancing the system. Our findings from this study open a new option. The numerical modeling of PV systems with strings of different length in parallel to several others which have an equal module count renders mismatch losses below 1% for most system configurations. For configurations where one string is one module shorter than the others, the mismatch losses fall below 0.5%. Therefore strings with unequal length may favorably connect to a cost-effective single-MPP inverter without causing significant energy yield losses. Moreover, typical thin film PV modules are less sensitive to mismatch than crystalline silicon based ones. (C) 2014 Elsevier Ltd. All rights reserved.

This paper presents a comparison of the annual performance loss rate (PLR) of twelve different grid-connected photovoltaic (PV) technologies based on outdoor field measurements. The annual DC performance loss rates of the installed PV technologies are obtained by using linear regression and classical series decomposition applied on the monthly DC performance ratio (PR) time series over five years (June 2006-June 2011). The PLR values obtained over the five-year period differ by up to 0.65% per year depending on the selection of the applied analysis method. The choice of the analysis technique affects the resulting PLR value but not the performance loss trend exhibited over the evaluation period for most technologies. Finally, there is evidence that the duration of the data used in the analysis affects the results as the PLR pattern exhibited by the crystalline-silicon (c-Si) and copper indium gallium diselenide (CIGS) technologies demonstrates a gradual convergence towards a steady state value over the five-year period, whereas more time is required to reach steady state for the thin-film technologies of amorphous silicon (a-Si) and cadmium telluride (CdTe). (C) 2014 Elsevier Ltd. All rights reserved.

Due to its high energy density, theoretical studies propose silicon as a promising candidate material for metal-air batteries. Herein, for the first time, experimental results detail the use of n-type doped amorphous silicon and silicon carbide as fuel in Si-air batteries. Thin-film silicon is particularly interesting for flexible and rolled batteries with high specific energies. Our Si-air batteries exhibit a specific capacity of 269 Ah kg(-1) and an average cell voltage of 0.85 V at a discharge current density of 7.9 mu A cm(-2), corresponding to a specific energy of 229 Wh kg(-1). Favorably in terms of safety, low concentrated alkaline solution serves as electrolyte. Discharging of the Si-air cells continues as long as there is silicon available for oxidation.

In this work, the seasonal performance of different grid-connected photovoltaic technologies installed both in the warm climate of Nicosia, Cyprus, and in the moderate climate of Stuttgart, Germany, was evaluated. The technologies presented include mono-crystalline-silicon, multi-crystalline-silicon and thin-film amorphous-silicon, cadmium-telluride and copper-indium gallium-diselenide technologies. The crystalline-silicon technologies exhibited maximum performance ratio (PR) peaks during the winter and minimum peaks during the warmer summer seasons in Nicosia. This signifies that the performance of these technologies installed in the warm climate is strongly dependent on temperature. The identical type crystalline-silicon technologies in Stuttgart exhibited a similar behaviour as in Nicosia with the exception of rapid decreases in performance due to snow in the winter. In contrast, the amorphous-silicon thin-film technologies exhibited a different seasonal performance compared with the remaining installed technologies, as their operating PR was higher during the summer and autumn months and lower during the winter.

Spatially resolved measurements of minority carrier lifetime are a valuable tool to monitor the quality of silicon wafers and of single processing steps. Common implementations of this technique generate excess minority carriers by scanning the variable focus of a pulsed light beam over the wafer surface. The resulting carrier distribution is spatially inhomogeneous; therefore minority carriers diffuse out of the illuminated area. However, most existing evaluation models neglect carrier diffusion, and hence overestimate the photogenerated minority carrier concentration by several orders of magnitude. This contribution presents a simulation model to calculate the correct local minority carrier concentration due to carrier diffusion for variable line and spot focus geometries. Carrier density distributions from spatially resolved photoluminescence measurements confirm the results of the model.

This paper analyzes the impact of hydrogen on the photoluminescence (PL) efficiency of the three wide gap silicon alloys: silicon carbide (a-SiCx), silicon nitride (a-SiNx): silicon oxide (a-SiOx). All three materials behave similarly. The progression of the PL efficiency over the Si content splits into two regions. With decreasing Si content, the PL efficiency increases until a maximum is reached. With a further decrease of the Si content, the PL efficiency declines again. A comprehensive analysis of the sample structure reveals that the PL efficiency depends on the degree of passivation of Si and Y atoms (Y = C, N, O) with hydrogen. For samples with a high Si content, an effective passivation of incorporated Y atoms gives rise to an increasing PL efficiency. The PL efficiency of samples with a low Si content is limited due to a rising amount of unpassivated Si defect states. We find that a minimum amount of 0.2 H atoms per Si atom is required to maintain effective luminescence.

Local shading during thin film deposition monolithically interconnects thin film solar cells into photovoltaic modules. This in-situ series connection method is, for the first time, applied to an amorphous silicon tandem cell structure. Sequential maskingand mask-shifting forms the electrical series connection in-situ, i.e. during the sputtering and plasma depositions of the contact and semiconductor layers of the thin film solar cell structure. The resulting photovoltaic module consists of five amorphous silicon tandem cells with a total module area A(m) = 12.5 cm(2). The module exhibits a fill factor FFm > 72% and a total area efficiency eta(m) = 6.2%. Thermographic imaging proves successful patterning by local shading and attributes low shunt resistances of some component cells to single pinhole formation. The dark-shunt resistance of each cell of the module amounts to R-sc.dark.cell > 13 k Omega cm(2) and for the complete module to R-sc.dark.module = 454 k Omega cm(2). ((c) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)