The aim of this paper is to shed some light on what difference the quality of a PV product makes to the customer and how much effort is required to deliver it. From the customer’s point of view, the quality of a PV product is key to a worthwhile investment, since the value of a PV system is defined by its cost compared with its yield over the entire lifetime, or the levelized cost of electricity (LCOE). But while many manufacturers make more or less the same promises, in this paper a closer look is taken at what is really involved in living up to those promises. If quality is understood to be a fundamental attitude that is reflected in every single process along the entire value chain, only then will this eventually lead to high-quality products and services. The paper discusses in detail the principles, methods, tests and processes required to secure a superior quality brand.
There have been encouraging signs in recent months of changing fortunes for PV equipment suppliers after a difficult period of consolidation. Shipment figures, actual and forecast, have in many instances seen an upswing, as booming markets in Japan, China and the US continue to drive demand, even as some European markets continue to dwindle. It’s probably too early to call the beginnings of a new PV technology buy cycle, but it seems more a case of ‘when’ rather than ‘if ’ now, and analysts have pointed to mid-2014 as the likely point when supply and demand will be in some kind of equilibrium. Clearly the implication of this is that if demand continues to rise beyond this point, supply will have to keep up, so manufacturers will have to invest in new capacity.
Passivated emitter and rear cells (PERC) are considered to be a next generation of industrial solar cells, and several companies have already started pilot production. The much-reduced rear-surface recombination in PERC cells requires improvements to the front side, for example the emitter, in order to further increase the conversion efficiency in the future. This paper presents an evaluation of the emitter technologies of three industrially applicable PERC cell concepts: 1) with an ion-implanted emitter, 2) with a chemically polished rear surface, and 3) with a selective emitter formed by gas phase etch-back (GEB). The results are compared with a reference high-efficiency POCl3-diffused PERC cell. The three industrial PERC concepts utilize lean industrially applicable process flows which reduce the phosphorus concentration at the wafer surface.
Accordingly, when compared with the POCl3-diffused emitter, the ion-implanted and GEB emitters obtain significantly lower emitter saturation current densities of 40 to 60fA/cm2 for emitter sheet resistances of 90 to 130Ω/sq. When applied to large-area PERC cells with screen-printed metal contacts, the ion-implanted and GEB emitter cells demonstrate up to 10mV higher open-circuit voltages than the POCl3-diffused reference PERC cell, and achieve conversion efficiencies of 20.0 and 20.3%, respectively. The next steps in further increasing the efficiency are outlined.
According to the ITRPV (International Roadmap for PV), a large fraction of future solar cells will be n-type and rear-contact cells with the highest efficiencies and fabricated using low-cost processes. As the standard p-type silicon solar cell in mass production is completely optimized and has therefore reached its cost limit, it is currently very difficult for new solar cell concepts to be cost effective from the outset when introduced into production. Consequently, in the current market situation, the introduction of new solar cell concepts to the market is not straightforward. The only way to achieve this is to use the fully adapted standard processes employed in today's manufacturing lines and only upgrade them with a few industrially approved process steps – such as laser ablation and boron diffusion – in order to implement low-cost device structures with stable efficiencies well above 20%. This paper gives an overview of n-type cell concepts already present on the market and of promising technologies ready for pilot production; the latter were summarized and discussed at the 3rd nPV workshop in April 2013 in Chambéry, France. The consequences for module manufacturing, as well as for measurement techniques and for requirements in respect of new standardization for cell and module characterization, will also be discussed..
As the PV capacity of utility systems increases, utility planners and operators are becoming more and more concerned about the potential impacts of power supply variability caused by transient clouds. Utilities and control system operators need to adapt their planning, scheduling and operating strategies to accommodate this variability while at the same time maintaining existing standards of reliability. Effective management of these systems, however, requires a clear understanding of PV output variability and the methods to quantify it. The present objective is to develop analytical methods and tools to quantify PV fleet output variability. This paper presents a method using location-specific inputs for estimating correlation coefficients, and discusses the key findings that resulted from applying the method to three separate geographical regions in the USA. The approach has potential financial benefits for systems that are concerned about PV power output variability, ranging from individual distribution feeders to state-wide balancing regions.
Whether in the USA as a part of a manufacturing resurgence or elsewhere in the world, solar producers need to be smarter than ever about where they choose to locate new operation centres. Solar manufacturing site selection
demands analytical rigour. The intent of this article is to share strategies and tools that can help owners make the best informed choices about where to locate new manufacturing operations.
Even in the competitive and turbulent present-day PV market, thin-film PV modules based on copper indium gallium selenide (CIGS) have good prospects for capturing a growing market share. Three important factors support the survival and growth of CIGS technology on the market: 1) proven lab results demonstrate considerable room for improvement of conversion efficiency; 2) the potential for cost reduction is high (reduced equipment CAPEX as well as reduced material and BOS costs); and 3) a high degree of freedom in the choice of substrate material and shape
enables efficient application of the technology. These factors should be realized using more-generic or standardized CIGS production equipment to reach economy of scale. Examples of novel and improved strategies for cost-efficient thin-film deposition and absorber formation are presented in this paper. Within the framework of a new thin-film PV research alliance under the name Solliance, a CIGS demonstrator line has recently become available for accelerating R&D of cost-effective processes and equipment, and for demonstrating their capabilities in improving CIGS in terms of
product performance and lifetime..
Despite considerable progress in screen-printing processes for crystalline silicon solar cell metallization, alternatives are still of interest because of their potential cost and performance advantages. Plating processes are one alternative that can be either combined with printed seed layers or used for full front-contact deposition. Although there are advantages to both approaches, there are also challenges that must be faced. Plating nickel and copper onto printed seed layers is very simple and involves only minor process modifications. With regard to undesired paste–electrolyte interaction, noticeable progress has been made during the past few months, bringing this process closer to industrial implementation. Plating nickel directly onto silicon offers the possibility of contacting emitters even with a surfacedoping concentration as low as 8×1018cm-3, while achieving similar performance to that of an evaporated contact metallization. To obtain sufficient adhesion, an in-depth understanding of the interface processes during silicidation is necessary. Gaining this understanding has enabled high peel forces greater than 2N/mm to be realized using a standard solder-and-peel procedure at a 90-degree angle. Process simplification will make such a process highly attractive for solar cell metallization, which is all the more important, as high-efficiency concepts are appearing that require advanced metallization schemes.
Statistical data on potential-induced degradation (PID) testing at the panel level are discussed in terms of their field relevance and the actual occurrence of PID in the field, since the latter is strongly dependent on both the specific climate and the weather conditions at a certain location as well as on the system configuration realized in a specific power plant. The correlation of outdoor conditions and leakage current is also considered with regard to a suitable standard test for solar panels. Real outdoor data are shown for PID-affected power plants. Indoor and outdoor recovery is demonstrated for PID in real solar plants as well as in lab and outdoor set-ups. Apart from ‘measuring’ PID in suitable tests and in the field, approaches are also presented for the mitigation of PID at the panel and system level.
This paper presents recent developments of ECN’s n-Pasha (passivated on all sides H-pattern) solar cell technology. The n-Pasha cell, currently being produced on an industrial scale by Yingli Solar, is a solar cell fabricated on n-type Cz material with homogeneous diffusions, dielectric passivation and printed metallization on both sides. The metallization is applied in an open H-pattern to both sides, which makes it suitable for bifacial applications. In order to improve both cell performance and the cost of ownership of n-Pasha solar cells, the ECN R&D team has focused on several aspects of the device design and processing. By reducing metal coverage and improving the quality of the front-side metallization, tuning the back-surface field (BSF) doping and improving the front- and rear-surface passivation, it has been possible to obtain an average efficiency of 20%, with top efficiencies of 20.2%. At the same time, the amount of silver used for metallization
has been decreased by over 50% and is now similar to that used for p-type solar cells. Furthermore, it is shown that with the ECN n-Pasha cell concept, wafers from the full resistivity range of n-Cz ingots can be used to make cells without losses in efficiency. Combining the improved efficiency and the reduction in cost makes the n-Pasha cell concept a very cost effective solution for manufacturing highly efficient solar cells and modules.
