Relationships between diffusion parameters and phosphorus precipitation during the POCl3 diffusion process

The POCl3 diffusion process is still a common way to create the pn-junction of Si solar cells. Concerning the screen-printing process, it is necessary to find a compromise between low emitter recombination, low contact resistance and high lateral conductivity. The formation of a homogeneous emitter during the POCl3 diffusion process depends on several diffusion parameters, including duration, temperature and gas flow. This primarily controls the growth of the highly doped phosphosilicate glass (PSG) layer, which acts as a dopant source during the diffusion process. Detailed investigations of the PSG layer have shown a distinct correlation between the process gas flows and the composition of the PSG layer. Specifically, in this research we examine the influence of phosphorus precipitation at the PSG/Si interface. Furthermore, we show the influence of phosphorus precipitation during the pre-deposition phase on the passivation quality of the corresponding emitter. In a second step, we use the results to create emitters with a reduced density of phosphorus precipitates. In a last step, the optimized emitter structure was transferred to screen-printed solar cell processes, whereby efficiencies up to 19.4% abs. were achieved on monocrystalline p-type Cz material with full area Al-BSF rear side

New mechanistic model to simulate microalgae growth

The prospect of treating wastewater and at the same time producing microalgae biomass is receiving increasing attention. Mechanistic models for microalgae growth in wastewater are currently being developed for new systems design as well as to improve the understanding of the involved biokinetic processes. However, mathematical models able to describe the complexity of microalgal cultures are still not a common practice. The aim of the present study is to present and calibrate a new mechanistic model built in COMSOL Multiphysics™ platform for the description of microalgae growth. Carbon-limited algal growth, transfer of gases to the atmosphere; and photorespiration, photosynthesis kinetics and photoinhibition are included. The model considers the growth of microalgae as a function of light intensity and temperature, as well as availability of nitrogen and other nutrients. The model was calibrated using experimental data from a case study based on the cultivation of microalgae species in synthetic culture medium. The model was able to reproduce experimental data. Simulation results show the potential of the model to predict microalgae growth and production, nutrient uptake, and the influence of temperature, light intensity and pH on biokinetic processes of microalgae.Peer ReviewedPostprint (author's final draft

“Angular resolution expected from iCHORD orientation maps through a revisited ion channeling model”

International audienceCrystalline orientation maps are obtained in a Focused Ion Beam (FIB) microscope using the ion CHanneling ORientation Determination (iCHORD) method, which relies on the channeling phenomenon observed in ion-induced secondary electron images. The current paper focuses on the angular resolution that can be expected from such orientation maps, obtained using a revisited ion channeling model. A specific procedure was developed to evaluate the angular resolution, based on the distribution of orientation errors when evaluating controlled sample disorientation. The main advantage is that no external reference is required. An angular resolution of 1° is obtained on a nickel based sample using standard acquisition conditions. This value fulfills most of the needs in terms of microstructural characterization usually carried out by Electron Back Scattered Diffraction

Functional behaviour of TiO2films doped with noble metals

To evaluate the effects of different concentrations of noble metal in a TiO2 matrix, different films of both Ag:TiO2 and Au:TiO2 systems were prepared. Mechanical and tribological characterization was carried out to evaluate the coatings response as a function of the noble metals composition and (micro)structure of the films. The overall set of results indicates that the amorphous films reveal better results than the crystalline ones. For the amorphous samples, the reduced Young’s modulus and the adhesion critical loads followed similar tendencies in both sets of films. Wear rates were similar for all samples except for the one with the highest silver content. To improve brittleness of TiO2 films, the results seem to indicate that a slight metal doping is preferred, and Au showed to be a better choice than Ag. In fact, the sample with the lowest Au content revealed a better mechanical behaviour than the pure TiO2 film.This research was sponsored by FEDER funds through the COMPETE program (Programa Operacional Factores de Competitividade) and by FCT (Fundação para a Ciência e a Tecnologia), under the projects PEST-C/FIS/UI607/2013 and PEst-C/EME/UI0285/2013. The authors also acknowledge the financial support by the project Nano4color – Design and develop a new generation of color PVD coatings for decorative applications (FP7 EC R4SME Project No. 315286)

Optimizing phosphorus diffusion for photovoltaic applications: Peak doping, inactive phosphorus, gettering, and contact formation

The phosphosilicate glass (PSG), fabricated by tube furnace diffusion using a POCl3 source, is widely used as a dopant source in the manufacturing of crystalline silicon solar cells. Although it has been a widely addressed research topic for a long time, there is still lack of a comprehensive understanding of aspects such as the growth, the chemical composition, possible phosphorus depletion, the resulting in-diffused phosphorus profiles, the gettering behavior in silicon, and finally the metal-contact formation. This paper addresses these different aspects simultaneously to further optimize process conditions for photovoltaic applications. To do so, a wide range of experimental data is used and combined with device and process simulations, leading to a more comprehensive interpretation. The results show that slight changes in the PSG process conditions can produce high-quality emitters. It is predicted that PSG processes at 860?°C for 60?min in combination with an etch-back and laser doping from PSG layer results in high-quality emitters with a peak dopant density Npeak?=?8.0?×?1018?cm?3 and a junction depth dj?=?0.4?m, resulting in a sheet resistivity?sh?=?380 ?/sq and a saturation current-density J0 below 10 fA/cm2. With these properties, the POCl3 process can compete with ion implantation or doped oxide approaches

ENTRAP and its potential interaction with European networks

AbstractENTRAP comprises a pan-European cooperation of leading scientific institutions and regulatory bodies in the field of nuclear-waste characterization and its quality assurance for the safe disposal of radioactive waste. Here, the scope of this cooperation is presented and explained and links or interfaces for a potential collaboration with partners fulfilling tasks of IDG-TP are pursued

Macromolecular and electrical coupling between inner hair cells in the rodent cochlea

Inner hair cells (IHCs) are the primary receptors for hearing. They are housed in the cochlea and convey sound information to the brain via synapses with the auditory nerve. IHCs have been thought to be electrically and metabolically independent from each other. We report that, upon developmental maturation, in mice 30% of the IHCs are electrochemically coupled in ‘mini-syncytia’. This coupling permits transfer of fluorescently-labeled metabolites and macromolecular tracers. The membrane capacitance, Ca2+-current, and resting current increase with the number of dye-coupled IHCs. Dual voltage-clamp experiments substantiate low resistance electrical coupling. Pharmacology and tracer permeability rule out coupling by gap junctions and purinoceptors. 3D electron microscopy indicates instead that IHCs are coupled by membrane fusion sites. Consequently, depolarization of one IHC triggers presynaptic Ca2+-influx at active zones in the entire mini-syncytium. Based on our findings and modeling, we propose that IHC-mini-syncytia enhance sensitivity and reliability of cochlear sound encoding