Search

Within the framework of research carried out by our team aimed at developing new immunological methods to determine proteins such as immunoglobulins G in different biological matrixes, for instance, serum and milk, tests were performed on several immunosensors based on different transducer types, i.e. amperometric (classical or screen-printed) electrodes for hydrogen peroxide. Lastly the feasibility of constructing immunosensors based on surface plasmon resonance (SPR) was investigated. "Competitive" immunological procedures were used in the first two cases. Conversely, the surface plasmon resonance transduction technique allowed a "direct" measurement. Applications were performed on human serum, powdered milks for babies and particularly on several animal milks, in the case of buffalo milk seeking a routine control method to identify possible inflammatory affections in the animals.

A Simple way to improve solar cell efficiency is to enhance the absorption of light and reduce the shading losses. One of the main objectives for the photovoltaic roadmap is the reduction of metalized area on the front side of solar cell by fin lines. Industrial solar cell production uses screen-printing of metal pastes with a limit in line width of 70-80 μm. This paper will show a combination of the technique of laser grooved buried contact (LGBC) and Screen-printing is able to improve in fine lines and higher aspect ratio. Laser grooving is a technique to bury the contact into the surface of silicon wafer. Metallization is normally done with electroless or electrolytic plating method, which a high cost. To decrease the relative cost, more complex manufacturing process was needed, therefore in this project the standard process of buried contact solar cells has been optimized in order to gain a laser grooved buried contact solar cell concept with less processing steps. The laser scribing process is set at the first step on raw mono-crystalline silicon wafer. And then the texturing etch; phosphorus diffusion and SiNx passivation process was needed once. While simultaneously optimizing the laser scribing process did to get better results on screen-printing process with fewer difficulties to fill the laser groove. This project has been done to make the whole production of buried contact solar cell with fewer steps and could present a cost effective opportunity to solar cell industries. In collaboration with Institute for Photovoltaics IPV, University of Stuttgart.

Conventional screen-printed crystalline silicon solar cell technology has dominated the photovoltaic industry for three decades. The key strengths of the technology are its robustness, simple processing and ready availability of the required processing equipment. Its performance is limited by several fundamental factors however. The largest performance losses arise from the inability to reliably print finer lines and the requirement for a heavily-doped emitter, which provides the cell with very poor short wavelength response. This thesis aims to overcome these limitations, initially through the development of techniques for creating a homogeneous and lightly-diffused emitter with sufficiently deep junction to be compatible with screen-printed contacts. It has been shown that by changing the doping profile of the emitter, excellent short wavelength response is achieved, and contact resistance losses for such an emitter can be reduced to acceptable levels, leading to respectable fill factors. For further improvement, a novel semiconductor finger solar cell design has been proposed and developed that effectively facilitates the formation of a selective emitter for screen-printed contacts but without requiring any alignment or close spacing of metal lines. The semiconductor fingers can be formed by laser grooving the lightly-doped Si surface and then heavily doping the groove walls via high temperature furnace diffusion. The current-carrying ability of these semiconductor fingers eliminates the requirement for a heavily-diffused top surface emitter and corresponding poor short wavelength response. In addition, they simultaneously allow screen-printed metal fingers to be placed further apart, therefore compensating for the inability to print narrower screen-printed lines, thus reducing shading. The addition of semiconductor fingers to the lightly-doped emitter enables fill factors as high as 79% to be achieved with standard screen-printing metallisation. Standard commercially-deposited PECVD silicon nitride has been shown capable of providing excellent surface passivation of the lightly-doped emitter, as demonstrated by the device’s excellent short wavelength response and open circuit voltages close to 640 mV. Cell efficiency of 18.4% has been demonstrated on 155 cm2 solar-grade p-type CZ wafers. Laser doping has been investigated as a method for simplifying and lowering the cost for forming semiconductor fingers by replacing laser grooves with laser-doped lines. Finally, the potential benefits of using n-type CZ wafers instead of p-type CZ wafers are evaluated through an innovative rear emitter solar cell design and processing techniques. Commercial screen-printed aluminium pastes have been used to form an aluminium-doped p+ emitter on the entire rear surface using a modified firing process. Open circuit voltages close to 650 mV and fill factors approaching 80% demonstrate the success in this cell design in eliminating both junction shunting and resistive losses that commonly limit screen-printed solar cells to much lower efficiencies. Efficiencies as high as 18.7% have been achieved with this cell design using large area solar-grade n-type CZ wafers.

This paper describes a procedure for the determination of antimony (III) by differential pulse anodic stripping voltammetry using a mercury film screen-printed electrode as the working electrode. The procedure has been optimized using experimental design methodology. Under these conditions, in terms of Residual Standard Deviation (RSD), the repeatability (3.81 %) and the reproducibility (5.07 %) of the constructed electrodes were both analyzed. The detection limit for Sb (III) was calculated at a value of 1.27×10–8 M. The linear range obtained was between 0.99 × 10–8 – 8.26 × 10–8 M. An analysis of possible effects due to the presence of foreign ions in the solution was performed and the procedure was successfully applied to the determination of antimony levels in pharmaceutical preparations and sea water samples.

Screen-printed electrodes coated with the nation layer have been investigated for cholinesterase biosensor design. The butyrylcholinesterase (ChE) from horse serum was immobilised onto the nation layer by cross-linking with glutaraldehyde vapours. The biosensors obtained showed better long-term stability and lower working potential in comparison to those obtained with no nation coating. The sensitivity of a biosensor toward organophosphate pesticides is not affected by the nation coating. The detection limits were found to be 3.5 x 10-7 M for trichlorfon and 1.5 x 10-7 M for coumaphos. (C) 2000 Elsevier Science B.V. | Screen-printed electrodes coated with the nafion layer have been investigated for cholinesterase biosensor design. The butyrylcholinesterase (ChE) from horse serum was immobilized onto the nafion layer by cross-linking with glutaraldehyde vapours. The biosensors obtained showed better long-term stability and lower working potential in comparison to those obtained with no nafion coating. The sensitivity of a biosensor toward organophosphate pesticides is not affected by the nafion coating. The detection limits were found to be 3.5×10-7 M for trichlorfon and 1.5×10-7 M for coumaphos.

In this paper, we investigate the surface recombination of local screen-printed aluminum contacts applied to rear passivated solar cells. We measure the surface recombination velocity by microwave-detected photoconductance decay measurements on test wafers with various contact geometries and compare two different aluminum pastes. The aluminum paste which is optimized for local contacts shows a deep and uniform local back surface field that results in Smet = 600 cm/s on 1.5 Ωcm p-type silicon. In contrast, a standard Al paste for full-area metallization shows a nonuniform back surface field and a Smet of 2000 cm/s on the same material. We achieve an area-averaged rear surface recombination velocity S rear = (65 ± 20) cm/s for line contacts with a pitch of 2 mm. The application of the optimized paste to screen-printed solar cells with dielectric surface passivation results in efficiencies of up to 19.2 % with a Voc = 655 mV and a Jsc = 38.4 mA/cm2 on 125×125 mm2 p-type Cz silicon wafers. The internal quantum efficiency analysis reveals Srear = (70 ± 30) cm/s which is in agreement with our lifetime results. Applying fine line screenprinting, efficiencies up to 19.4 % are demonstrated. German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety/0327529A

Barium titanate thick films were prepared from mechanically activated powders based on BaCO3 and TiO2. The thick films were screen-printed on alumina substrates electroded with Ag/Pd. The BT films were sintered at 850 degreesC for 1 hour. The thickness was 30-75 mum depending of number of layers. The microstructure of thick films and the compatibility between BT layers and substrate was investigated by SEM. The dielectric properties were measured and the results were reported.

Trace metal speciation is key to understand/predict bioavailability and potential toxicity of metals to biota and will, undoubtedly, be incorporated in future regulations. Electroanalytical methods have a role to play in such development: they offer a wide range of advantages such as speed, portability, economy, solid interpretation backgrounds and low limits of quantification. This review focusses on three selected stripping techniques: Competitive-Ligand Exchange - Cathodic Stripping Voltammetry (CLE-CSV), Scanned Stripping Chrono-Potentiometry (SSCP) and AGNES (Absence of Gradients and Nernstian Equilibrium Stripping) reporting their working principles, characteristics (strong and weak points) and recent applications to systems of environmental relevance (such as seawaters, freshwaters or soil extracts). The authors from the Universitat de Lleida gratefully acknowledge financial support from the Spanish Ministry MINECO (Project CTM2016-78798).