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We present a holistic approach for the photovoltaic (PV) module frame improvement that considers mechanical, electrical, economic, and ecological aspects for different frame designs. In a comprehensive study, the approach is applied to exemplary PV module frame designs. The analyses performed in this study show a potential improvement path of the module frame design. This leads to an overall better module performance and helps finding the balance point between technical performance, cost, and environmental impact. Based on the results, the PV module frame design affects the aspects analyzed in this work differently. For the comparison, we defined reference frame design with 16 and 20 mm front and rear frame widths. The improvement is reached by unitizing the frame width for both sides to 18 mm and increasing its cavity width to 12 mm instead of 8.5 mm. Tuning the frame parameters in this way leads to the best balance point for frame designs in this study regarding all aspects. The mechanical finite element method (FEM) simulation results show that even a small change on the frame width has a significant influence on the stress within the solar cells. Compared with the reference frame, the optimized frame design shows 2.6% less deflection, which corresponds to around 0.7 mm. Cell-to-module (CTM) analysis shows that a bigger frame width lightly decreases the cover coupling power gain. Results show that increasing the front frame width from 16 to 20 mm reduces the module power by about 0.12 WP. Findings of the cost of ownership (COO) analysis suggest that the optimized frame can save around 30 g aluminum which reduces the total module cost by 0.1%. Life cycle assessment (LCA) results are directly correlated to the material mass of the corresponding design. Results show that using the optimized frame can save 0.8 kg CO2-eq/kWP due to the saving in aluminum compared with the reference frame.

Sufficiently deep local back-surface-fields (LBSF) are crucial for achieving low contact recombination and thus high solar cell efficiencies in passivated emitter and rear contact (PERC) solar cells. In this article, we investigate spatial variations of LBSF thickness 1) across dashed contacts, 2) between lateral positions within a cell, and 3) from cell to cell. The objective of this experimental study is to proof the impact of LBSF thickness on open-circuit voltage in PERC solar cells. Our measurements and analysis of variance (ANOVA) reveal that variations in LBSF thickness across dashed contacts exceed observed variations in LBSF thickness between lateral positions within a cell as well as cell-to-cell variations. Thus, we statistically treat all LBSF measurements of a single experimental group of PERC solar cells as one population of measurements. The two investigated experimental sets of PERC cells fired using different fast-firing profiles show a difference in LBSF thickness of about 1 μm. The resulting difference in open-circuit voltages arises to 1.3 mV. ANOVA-based analysis shows for our experimental samples that at least 19 random measurements are necessary in order to resolve LBSF thickness difference of 0.5 μm with sufficient statistical significance.

We propose silicon solar cell–integrated stress and temperature sensors as a new approach for the stress and temperature measurement in photovoltaic (PV) modules. The solar cell–integrated sensors enable a direct and continuous in situ measurement of mechanical stress and temperature of solar cells within PV modules. In this work, we present a proof of concept for stress and temperature sensors on a silicon solar cell wafer. Both sensors were tested in a conventional PV module setup. For the stress sensor, a sensitivity of (−47.41 ± 0.14)%/GPa has been reached, and for the temperature sensor, a sensitivity of (3.557 ± 0.008) × 10$^{-3}$ K$^{-1}$ has been reached. These sensors can already be used in research for increased measurement accuracy of the temperature and the mechanical stress in PV modules because of the implementation at the precise location of the solar cells within a laminate stack, for process evaluation, in‐situ measurements in reliability tests, and the correlation with real exposure to climates.

We present an evaluation of the silicon solar cell as well as the photovoltaic (PV) module size and its effect on thermomechanical stress. The evaluation is based on finite-element method (FEM) simulations. Within these simulations, we perform parameter variations of the number of solar cells within a PV module from 60-140 cells, of the cell size from 156.0-161.75 mm, and the cell format from full cells down to quarter cells. The FEM simulations cover the lamination process, mechanical load, and thermal cycling for glass-foil as well as glass-glass modules. The presented results reveal correlations between the solar cell and module size with the stress in the solar cells. We also find that the interaction of the laminate with the module frame plays a significant role in thermal cycling. Of the varitations under investigation, the increase in cell size has the largest effect on the stress. However, at a mechanical load of 2400 Pa, glass-foil modules with less than 96 solar cells have a negligible failure probability. The advantage of placing the solar cells in the neutral axis of the laminate is proven by the negligible tensile stress values for all variations of the glass-glass modules.

We present a set of thermomechanical design rules to support and accelerate future (PV) module developments. The design rules are derived from a comprehensive parameter sensitivity study of different PV module layers and material properties by finite element method simulations. We develop a three dimensional finite element method (FEM) model, which models the PV module geometry in detail from busbar and ribbons up to the frame including the adhesive. The FEM simulation covers soldering, lamination, and mechanical load at various temperatures. The FEM model is validated by mechanical load tests on three 60-cell PV modules. Here, for the first time, stress within a solar cell is measured directly using stress sensors integrated in solar cells (SenSoCells®). The results show good accordance with the simulations. The parameter sensitivity study reveals that there are two critical interactions within a PV module: (1) between ribbon and solar cell and (2) between front/back cover and interconnected solar cells. Here, the encapsulant plays a crucial role in how the single layers interact with each other. Therefore, its mechanical properties are essential, and four design rules are derived regarding the encapsulant. Also four design rules concern front and back sides, and three address the solar cells. Finally, two design rules each deal with module size and frame, respectively. Altogether we derive a set of 15 thermomechanical design rules. As a rule of thumb of how well a bill of material will work from a thermomechanical point of view, we introduce the concept of specific thermal expansion stiffness $ {\hat{E}}_{\alpha }=E\cdotp \alpha \cdotp {A}_{\mathrm{j}}\cdotp h $ as the product of Young's modulus E, coefficient of thermal expansion $\alpha$, joint area A$_{j}$, and materials height h. The difference between two materials is a measure of how much thermal strain one material can induce in another. A strong difference means that the material with the larger value will induce thermal strain in the other.

This article investigates the impact of the back-surface-field (BSF) thickness variation within a local aluminum contact on the performance of passivated emitter and rear contact solar cells. A significant difference of BSF thickness between contact endings and the center of dash-shaped contacts is verified experimentally by a comprehensive statistical analysis using scanning electron microscopy. The impact of local BSF thickness differences on the cell performance is studied with 3-D technology computer-aided design (TCAD) device simulations. Several device parameters such as BSF thicknesses, the doping concentration in the BSF profile at rear contacts, or the metallized area fraction at the cell rear side are varied. Our simulation study shows that the open-circuit voltage is mainly affected by locally reduced BSF thicknesses, resulting in an efficiency loss up to 0.14% abs or 0.84% abs , respectively, if an area fraction of 1% or 20% within a local contact has reduced BSF thicknesses. This effect can be minimized either by reducing the metallized area fraction at the cell rear side or by increasing the doping concentration in the BSF profile at aluminum rear contacts. In addition, we demonstrate that the 3-D simulations can be approximated with 2-D simulations by applying a single doping profile with an average BSF thickness, calculated with the harmonic mean.

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.

Many manufacturers choose the passivated emitter and rear cell (PERC) approach in order to surpass the 20% cell efficiency level in mass production. In this paper, we study the efficiency potential of the PERC approach under realistic assumptions for incremental improvements of existing technologies by device simulations. Based on the most recent published experimental results, we find that the PERC structure is able to reach about 24% cell efficiency in mass production by an ongoing sequence of incremental improvements. As a guideline for future developments, we provide a method to improve cell efficiency most effectively by monitoring the current losses at the maximum power point. By means of numerical device modeling, we identify some key technologies toward 24% efficient PERC cells and provide its technology-related target requirements.

This work aims to improve the rear-side properties of p -type monocrystalline silicon solar cells by using the passivated emitter and rear locally diffused (PERL) solar cell concept. To realize the rear side structure, the so-called PassDop approach was used combining both surface passivation and local doping. The concept utilizes a multifunctional, doped AlO x /SiN x :B layer stack; the localized structuring is achieved by local contact opening and doping by a laser process. Using AlO x /SiN x :B PassDop layers, an outstanding effective surface recombination velocity S eff of less than 4 cm/s was achieved after firing at the passivated area. The boron concentration in the PassDop layers did not show any significant influence on S eff . Laser doping resulted in highly doped regions in the silicon with a sheet resistance of below 20 Ω/sq and surface doping concentrations close to 1 × 1020 cm–3. Accordingly, calculations showed that the saturation current density at the laser doped areas can be as low as 900 fA/cm² for line-shaped contact structures.

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.

During the crystallization of directionally solidified silicon such as multicrystalline or cast quasi-single crystalline silicon, the diffusion of metal impurities from crucible and coating into the solid silicon ingot at high temperatures creates a severe contamination issue in the edge region of the ingot, the so called red zone. We present an effective diffusion barrier which greatly reduces this detrimental metal diffusion. Silicon wafers are coated with a layer system of silicon oxide and silicon nitride by chemical vapor deposition and are placed on the bottom of the crucible. Using this technique, the metal contamination in the red zone can be reduced by about one order of magnitude. This leads to better solar cell performance of wafers fabricated from this ingot area. Also, less ingot material has to be discarded leading to higher wafer yield per ingot.

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.

Im Jahr 2009 wurde eine neue Schraegseilbruecke ueber den Rhein bei Wesel fuer den Verkehr freigegeben und die alte Bruecke zurueckgebaut. Von den dazu vorzunehmenden Rueckbaumassnahmen wird der Abbruch des rechtsrheinischen Pfeilers beschrieben. Alle Unterbauten der alten Bruecke, so auch der beschriebene Pfeiler, waren bis zu einer Tiefe von 4,50 Metern unter Rheinsohle zu entfernen. Da wegen der direkt benachbarten neuen Rheinbruecke ein Rueckbau durch Sprengen nicht machbar war, musste der Pfeiler samt Fundament mit Hydraulikbaggern und sonstigen Abbaugeraeten abgebrochen werden. Der Rueckbau im Rhein erfolgte innerhalb einer Spundwandgrube, die wegen des Schiffsverkehrs zusaetzlich durch ein sehr grosses Leitwerk geschuetzt wurde. Die Spundwandgrube wurde im Grundriss als wasserdichter Kasten mit spitz zulaufenden Enden in Richtung Oberstrom und Unterstrom ausgefuehrt. Sowohl die Herstellung der Baugrube als auch die des Leitwerks werden anhand der einzelnen Arbeitsschritte detailliert beschrieben. Nach dem Abbruch von Pfeiler und Pfeilerfundament soll die Baugrube verfuellt werden. Danach folgt der Rueckbau des Spundwandkastens im Schutzes des Leitwerks und der Rueckbau des Leitwerks. Der linksrheinische Pfeiler liegt hinsichtlich des Schiffsverkehrs unkritischer, sodass die Baugrube ohne Schutz durch ein Leitwerk errichtet werden soll. ABSTRACT IN ENGLISH: After a new modern cable-stayed bridge across the Rhine was opened to traffic in 2009, the old bridge and its pillars has to be dismantled in the river Rhine. For the dismantling of the pillar a sheet piling pit was erected under the difficult conditions in the water sector. To protect it additionally a very large staging was built to protect the pit from damages with the large Rhine vessels travelling on the river Rhine. Under cover of the pit of the ancient massive pillars were dismantled conventionally. After dismantling the pillar deep below the riverbed, the staging and the pit were dismantled again. The work in the water sector and their special tasks are described. (A)

PERC (Passivated Emitter and Rear Cell) technology has been established as a new standard in silicon PV cell manufacturing whereby the deposition of the aluminum oxide (AlOx)/silicon nitride (SiNx) rear-side passivation stack is mainly performed by inline PECVD equipment. Simultaneously the industrial price pressure for cell and module manufactures increase by lower module prices. Thus further reductions of production costs per watt peak (Wp) are required. For this reason manufacturing equipment with higher throughput as well as a lower OPEX (operational expenditure) combined with high tool uptime and yield keeps being mandatory. PV tool suppliers are focused on developing new tool generations to meet those requirements by also supporting new cell technology improvements at once. Beside wet chemistry, diffusion and metallization tools especially new high quality and high-throughput passivation concepts for enhanced PERC (PERC+ [4]) cells are necessary. This paper shows results on Meyer Burgers new PECVD passivation equipment for enhanced PERC}+ cells including technologies like selective emitter and emitter oxidation. Those new passivation concepts can be applied for only rear side (MAiA ® 6.1) and even both sides (FABiA ® 4.1) of a PERC+ cell with throughputs up to 6000W/h and excellent deposition uniformity and quality.

Dark lock-in thermography (DLIT) combined with the ’local I-V’ method is applied to derive spatial-resolved efficiency losses and potentials for cast-mono PERC solar cells during wafer and cell developing phase. For the DLIT image evaluation method, four DLIT images at -1 V, 0.510 V, 0.555 V and 0.615 V as well as a lumped series resistance image from photoluminescence are measured at a cast-mono PERC solar cell exemplarily. From these five images, the ‘local I-V’ method derives locally I-V curves which allow spatial-resolved efficiency, open-circuit voltage and fill factor images. Main losses visible in the efficiency image could be separated into: small angle grain boundaries of the cast-mono wafer, stripe like contamination due to belt transportation within a wet bench, increased contact resistance at rear contacts at two sides of the cell and highly recombination active rear pad areas. The overall efficiency drop due to these local losses is calculated to about 0.8%abs.

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.

Passivated emitter and rear cell (PERC) solar cells are currently being introduced into mass production. In this paper, we report a novel PERC solar cell design that applies a screen-printed rear Al finger grid instead of the conventional full-area aluminum (Al) rear layer while using the same PERC manufacturing sequence. We name this novel cell concept PERC+ because it offers several advantages. In particular, the Al paste consumption of the PERC+ cells is drastically reduced to 0.15 g instead of 1.6 g for the conventional PERC cells. The Al fingers create 2-µm-deeper aluminum back surface fields, which increases the open-circuit voltage by 4 mV. The five-busbar Al finger grid enables bifacial applications of the PERC+ cells with front-side efficiencies up to 20.8% and rear-side efficiencies up to 16.5% measured with a black chuck. The corresponding bifaciality is 79%. When applied in monofacial modules where the white back sheet acts as external rear reflector, the efficiency of the PERC+ cells is estimated to 20.9%, which is comparable with conventional PERC cells. Whereas Institute for Solar Energy Research Hamelin developed the aforementioned PERC+ results, SolarWorld independently pioneered a very similar bifacial PERC+ cell process starting in 2014. Transfer into mass production has been successfully accomplished, and novel glass–glass bifacial PERC+ modules have been launched at the Intersolar 2015 based on a most simple, lean, and cost-effective bifacial cell process. These new bifacial PERC+ modules show an increase in annual energy yield between 5% and 25% in simulations, which is confirmed by first outdoor measurements. Copyright © 2015 John Wiley & Sons, Ltd.

To investigate the rear side of bifacial p-type Czochraslki-grown silicon PERC solar cells, the present work combines Sentaurus Device simulation – calibrated with extensively characterized samples – and the subsequent fabrication of solar cells according to the simulation findings. The authors investigate the physical alteration of rear-side characteristics in the context of an additional rear-side illumination. The additional injection represents an further factor for the balance of carrier generation, recombination and series resistances which in turn influences the design rules for the rear side layout. Our detailed bifacial simulations include these physical aspects and we derive design solutions for different bifacial illumination scenarios for a bifacial p-doped PERC solar cell. Using an industrial PERC process, solar cells with laser contact openings (LCO) and a rear aluminum grid were produced according to the simulation results with a wide variation in rear side layout parameters. The PERC batches showed a rather constant medium (front side) efficiency of η = 20.8±0.2% and a bifaciality of 66 to 77% depending on the rear layout, allowing us to investigate the rear-side characteristics in detail and to compare them with the effects predicted by the simulations. We processed an aluminum rear contact grid with finger widths as small as 100 µm and successfully aligned it onto the LCO with 30 µm contact openings on full-area 156x156 mm 2 wafers. We reached good accordance between the monofacial measurements from front and rear side and our simulation model and could thus predict bifacial illumination results by modeling for two issues: 1. Planar rear sides have an advantage over pyramid textured rear sides for 1000 W/m² front illumination unless additional rear illumination exceeds 250 W/m². 2. As soon as any rear illumination is added to the front-illuminated PERC solar cell, 100 µm thin fingers at the rear side have an output power advantage compared to 150 µm and 200 µm wide fingers.

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.

Die Stadtwerke Dusseldorf Netz GmbH betreiben derzeit ein Fernwarmenetz mit einer Lange von ca. 190 km, welches unter anderem vom Heizkraftwerk Lausward gespeist wird. Fur den zukunftsorientierten Ausbau des Fernwarmenetzes im Stadtgebiet Dusseldorf war die Anbindung der linksrheinisch gelegenen Stadtteile an das bestehende rechtsrheinische Fernwarmenetz notwendig. Eine Fernwarmeleitung quer durch den Rhein zwischen dem Heizkraftwerk und dem Stadtteil Heerdt sollte bis Ende 2012 die Verbindung herstellen. Design and construction of a long-distance heating culvert from Dusseldorf-Lausward to Dusseldorf Oberkassel The company “Stadtwerke Dusseldorf GmbH” is operating a net of approximately 190 km long-distance heating pipelines which is energized by the heating-plant “Lausward”. For the forward-looking development of the long-distance heating pipeline net it was necessary to cross the river Rhine to connect the districts left from the Rhine of the city Dusseldorf with a new efficient heating plant under construction. A new long-distance heating pipeline has to connect the Heating plant on the right side of the river Rhine with the city districts on the left side.

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 authors discuss industry related approaches at Fraunhofer ISE for bifacial p-type silicon solar cells, taking into account the well-known "passivated emitter and rear cell" (PERC), "passivated emitter and rear totally diffused" (PERT) and "passivated emitter and locally diffused" (PERL) architectures. In the case of PERC, challenges in terms of alignment, printability and the importance of bifaciality are addressed. In the case of PERT, a co-diffusion process is utilized to form the emitter and the back surface field simultaneously avoiding also critical shunts that can arise at the edges of such devices. For the PERL technology, the industrial feasible pPassDop approach is discussed. We report on front side energy conversion efficiencies for PERC of 21.4%, PERT of 20.5%, and PERL of 19.8%. Furthermore, bifaciality factors for PERC of 0.7, for PERT of 0.86, and for PERL of 0.89 are presented.

The state-of-the-art low-ohmic electrical contacting of highly boron-doped silicon surfaces is based on the use of screen-printed and fired silver-aluminum (Ag-Al) contacts. For these contacts, metal crystallites with depths of up to a few microns are observed at the interface. For screen-printed and fired Ag contacts on phosphorus-doped surfaces, the observed crystallite depths are much smaller. In this work, low-ohmic electrical contacting of local laser-doped p-type silicon surfaces with commercial pure Ag screen-printing paste are demonstrated. The doping layer is based on the "pPassDop" approach, which serves as a passivation layer on the rear side of p-type silicon solar cells. The specific contact resistances are measured down to 1 mu ohmb cm2 for p-type doping densities of about 3Ã1019cm-3 at the silicon surface and finger widths of around 55 mu m. Microstructure analysis reveals the formation of numerous small Ag crystallites at the interface with penetration depths o f less than 80nm. A first implementation of the "pPassDop" approach on 6-inch p-type Cz-Si bifacial solar cells using solely Ag contacts on both sides results in a peak front side energy conversion efficiency of 19.1%, measured on a black chuck with contact bars on both sides.

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.

In this paper the novel method MDP (microwave detected photoconductivity) [1–4] will be introduced to the field of contact less inline metrology at bricks. By the application of a widely advanced microwave detection technique, it is now possible to map minority carrier lifetime and photoconductivity simultaneously, with a so far unsurpassed combination of spatial resolution, sensitivity, and measurement speed. Beside these two parameters the iron concentration can be detected and analyzing the photoconductivity at steady state in comparison with the minority carrier lifetime, a lot of additional information can be derived. This paper will show first examples of minority carrier lifetime and photoconductivity maps, along with resistivity linescans and iron concentration maps of whole bricks measured inline. Furthermore simulations will be provided. Solving the transport equations for electrons and holes during the measurement at bricks, it can be proven that the measured effective lifetime deviates only lightly from the actual bulk lifetime. Furthermore it becomes clear that a steady state generation is more suited for brick measurements than non-steady state methods.

In 2006, around 86% of all wafer-based silicon solar cells were produced using screen printing to form the silver front and aluminium rear contacts and chemical vapour deposition to grow silicon nitride as the antireflection coating onto the front surface. This paper reviews this dominant solar cell technology looking into state-of-the-art equipment and corresponding processes for each process step. The main efficiency losses of this type of solar cell are analyzed to demonstrate the future efficiency potential of this technology. In research and development, more various advanced solar cell concepts have demonstrated higher efficiencies. The question which arises is “why are new solar cell concepts not transferred into industrial production more frequently?”. We look into the requirements a new solar cell technology has to fulfill to have an advantage over the current approach. Finally, we give an overview of high-efficiency concepts which have already been transferred into industrial production.

In this work we present our approach to realize an industrial process that allows cell efficiencies up to and above 21%. Based on a loss analysis we systematically investigate the feasible options to improve the efficiency with device simulations and production experiments. Subsequently we perform sensitivity analyses particularly for various silicon wafer materials to ensure stable process capability. Our best prototype process with optimized front and rear side passivation and enhanced laser contact patterning has demonstrated a maximum efficiency of 20.9% with a very high V OC of 670 mV on high-lifetime mono material. We were able to assemble 60-cell based modules with more than 305Wp.

In this work, we present our progress in the industrial p-type PERC technology [1, 2]. Based on device simulations we continuously develop an efficiency roadmap for a steady improvement of our PERC (passivated emitter and rear cell) process. Following this simulation based approach, we effectively improve the front side metallization and the emitter characteristics. Currently, our best prototype process has reached a conversion efficiency well over 21% which enables the manufacturing of a 60-cell based module with a power of 310W. Our best cell so far has a conversion efficiency of 21.5% which has been confirmed by the calibration laboratory of Fraunhofer ISE. This is to our knowledge the highest efficiency reported for industrial-size silicon solar cells with screen-printed metal front and rear contacts.