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This paper summarises the outcome of an analysis of stablecoins undertaken by the ECB Crypto-Assets Task Force. At the time of writing, the stablecoin debate lacks a common taxonomy and unambiguous terminology. This paper applies a definition that distinguishes stablecoins from existing forms of currencies – regardless of the technology used – and characterises stablecoin arrangements based on the functions they fulfil. This approach emphasises the role of technology-neutral regulation in preventing arbitrage, as well as comprehensive Eurosystem oversight, irrespective of stablecoins’ regulatory status. Against this background, this paper assesses stablecoins’ implications for the euro area based on three scenarios for the uptake of stablecoins: (i) as a crypto-assets accessory function; (ii) as a new payment method; and (iii) as an alternative store of value. While the first scenario is merely the continuation of the current state of the market and, thus far, has not posed concerns for the financial sector and/or central bank tasks, stablecoins of the type envisaged in the second scenario may reach a scale such that financial stability risks can become material, and the safety and efficiency of the payment system may be affected. The third scenario is both the least plausible and the most relevant from a monetary policy perspective. The paper concludes that the Eurosystem relies on appropriate regulation, oversight, and supervision to manage the implications of stablecoins (and the risks that stem from them) on its mandate and tasks under plausible scenarios. The Eurosystem continues monitoring the evolution of the stablecoin market and stands ready to respond to rapid changes in all possible scenarios.

We performed an extensive study of light induced degradation experiments in PERC solar cells made of Boron doped Cz Silicon material from several experimental crystals. Strong LeTID (Light and Elevated Temperature Induced Degradation) amplitudes were found in cells originating from the top and tail part of the crystals. A statistical analysis reveals a strong correlation to the bulk concentration of Aluminium in cells originating from wafers close to the tail. Close to the top, the LeTID effect is strongly enhanced whenever Oxygen precipitation occurs in the cell process.

The efficiency record of industrial type PERC solar cells exceeded 22% at the turn of the year 2015 to 2016. Our best screen-printed PERC solar cell reached 22.04% efficiency while the best cell batch showed a very narrow efficiency distribution. A detailed electrical and optical loss analysis of those industrial type high efficiency PERC solar cells is carried out which enables further optimization and strategic improvements. A variety of characterization data allows for a recombination current density, resistance and optical loss analysis based on numerical device simulation, analytical calculations and raytracing, respectively. The main recombination losses at maximum power point (MPP) occur in the homogenous and selective diffused regions of the emitter. A series resistance loss analysis is analytically performed. The emitter contribution to the lumped series resistance dominates the series resistance losses. The optical loss analysis performed with raytracing shows main reflection and absorption losses in the rear metal layer which is partly due to the light trapping capability of the PERC cells.

With efficiencies of industrial type PERC solar cells exceeding 22% and reduced electrical and optical losses in these high efficiency cells, it becomes more and more important for manufacturers to rely on high quality silicon wafers. In this contribution, we present data of the bulk excess carrier lifetime τ bulk and a doping density independent material quality parameter at maximum power point, the material saturation current density j 0,mat , of different p-type monocrystalline silicon materials. These values are obtained by measuring the effective carrier lifetime of neighbouring wafers of different thickness and thus eliminating the surface recombination contribution. We show that j 0,mat is an adequate parameter to evaluate the bulk quality of a given material. To further validate these findings, we compare the results to PERC cell efficiencies obtained with the same material.

This paper reviews and analyzes technological design options, which have become available to date for BIPV systems on roofs and facades, independently of specific products or building projects. This means that this survey does not analyze existing products or realized buildings, but provides an overview of the technologies for BIPV. The starting point is an analysis of the relevance of BIPV technologies for the decarbonization of energy systems, providing energy for direct use of electricity and sector coupling together with an analysis of the German BIPV market. The paper presents the wide range of technical design options for BIPV systems and categorizes and analyzes them to provide a structured overview. This comprises a detailed analysis of the design options for BIPV modules, in which not only the design options for the PV cell layer were comprehensively investigated, but also the different variants of embedding materials, front and rear cover materials, additional interlayers and electrical module layout. Two fundamental module-level design options were investigated in particular detail: The use of PV cells as basic elements of patterns and the use of color to conceal the PV cells. Subsequently, options for the design of complete electrical systems are reviewed, ranging from sub-module level design parameters to building energy systems. Design options for the constructional integration of BIPV modules in the building envelope complete the review of technological design possibilities.

In this paper, we present our progress in co-extrusion printing for fine-line metallization. With this technique, 30 µm wide and 20 µm tall front grid fingers are currently printed. Applied to industrial size cast silicon PERC solar cells, a world record conversion efficiency of 21.42% has been demonstrated. This result was achieved with a production-ready co-extrusion printer that runs at a throughput of 2700 wafers per hour. Furthermore, a printhead is presented that has been developed to enable co-extrusion printing on pseudo-square wafers. Finally the cost advantage of the technology is discussed.

This paper introduces the application of a coextrusion printing as a contact and mask-free fine line metallization technology for direct printing of narrow grid lines with a strongly enhanced aspect ratio. Coextrusion printed grid lines enhance short circuit current and lower series resistance through a higher number of filigree fingers. The silver and sacrificial paste that merge inside the nozzle are simultaneously extruded onto the wafer and form a silver paste structure smaller than every design feature inside the nozzle. After contact firing the grid lines become as narrow as 35 µm with an aspect ratio up to 0.7. A further shrinkage potential down to 23.7 µm width with an aspect ratio up to 0.62 has been demonstrated. Coextrusion printed grid lines outperform screen printed grid lines in a whole slew of geometrical and optical properties. As for example grid line width and height variation is as low as ±0.5 µm and the optical effective finger width is far smaller than the screen printed effective finger width. Due to these low effective finger widths the absolute effective shading of 96 coextrusion printed grid lines is less than half of the 80 screen printed grid lines. The calculated short circuit current gain, due to the lower effective shading was experimentally confirmed accordingly. Furthermore a benchmark test in a production like environment was performed. Hereby an absolute cell efficiency gain of +0.25% over screen printed metallization was confirmed and a cell efficiency gain of over +0.35% to +0.4% abs. can be assumed to be achieved by using a direct contacting coextrusion silver paste, which is comparable to state of the art screen printing pastes.

In this work we compare experimental results of an industrial passivated emitter and rear cell (PERC) high volume pilot line production in the SolarWorld Innovations technology center with a simulation model based on 2D Sentaurus Device Simulations The PERC solar cell design shows in a well-controlled experiment a 1.1% absolute higher median efficiency compared to the aluminium back surface field (Al-BSF) solar cell reference group. We derive a calibrated simulation model by the characterization of cells and test structures. We show that the simulation model reproduces well the measured I-V data. In consequence this enables us to estimate the solar cell performance when an applied process or silicon wafer parameters will be changed for further optimization. In the second part of this study we investigate the impact of front and rear side recombination on the solar cell parameters by simulation and sensitivity analysis. We show that the quality of the local BSF underneath the local rear contacts has an important impact on the electrical solar cell performance.

The W3C Semantic Sensor Network Incubator group (the SSN-XG) produced an OWL 2 ontology to describe sensors and observations — the SSN ontology, available at http://purl.oclc.org/NET/ssnx/ssn. The SSN ontology can describe sensors in terms of capabilities, measurement processes, observations and deployments. This article describes the SSN ontology. It further gives an example and describes the use of the ontology in recent research projects.

The W3C Semantic Sensor Network Incubator group (the SSN-XG) produced an OWL~2 ontology to describe sensors and observations --- the SSN ontology. The SSN ontology can describe sensors in terms of capabilities, measurement processes, observations and deployments. This article describes the SSN ontology. It further gives an example and describes the use of the ontology in recent research projects.