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The research project INFINITY focuses on design improvements for PV system components operating in different climatic regions. This topic gained pertinence in recent years due to increased installation rates worldwide with the highest growth rates in non-moderate climates. As PV components are not optimized to the respective climate zone, the target of the project is to gather failure data from PV installations in various climate zones. A standardized data input was achieved by using an extended format of the IEA PVPS Task 13 failure survey, allowing to enter PV system and failure information in rich detail. The components' and failure structure were elaborated by combining input from reliability workshop proceedings, PVPS Task 13 and project partners' experience in PV reliability testing. These structures were mapped into a database to collect and prepare the input for further statistical analysis. Collected data was filtered, offering a tidy data set of 1048 samples from 340 sub-systems from 45 countries worldwide. After data filtering, a power loss evaluation, a cluster analysis and a trend analysis were performed. This paper presents results of comparing PV module failures in different climate zones starting with a range of PV systems installed in the 1970s, to recently installed systems.

Over the last years, the development of innovative, fast and non-destructive characterisation techniques for the detection of PV-module failures and advanced analysis of yield losses in photovoltaic power plants has become a key challenge in scientific research. Besides standard on-site thermographic screening, several novel and easily applied methods were developed and successfully tested. They differ mainly in their possible field of application, their applicability in the detection of different failure types and their cost of setup and operation. In order to evaluate the boundary conditions of application for the various methods, different defective PV-modules were comparatively investigated with commercially available and innovative outdoor analysis methods. The results were evaluated with regard to error detection rate and economics. Based on this comparison, efficient operation and maintenance (O&M) measures for early and general failure detection within large power plants can be deducted.

In photovoltaics, the quality of the polymeric solar cell embedding material is of key importance for the long-term durability and performance of the PV modules. For the most common encapsulant, elastomeric ethylene vinyl acetate (EVA), the degree of crosslinking is a key issue in this respect. Raman spectroscopy was researched as a fully contact-free, truly non-destructive optical method to measure the degree of EVA crosslinking of bare EVA film samples as well as in-situ inside assembled PV modules. The method relies on evaluating subtle but characteristic spectral differences in the CH-stretching vibration region (3.000–2.800 cm −1 ) that correlate directly, unambiguously and reliably to the crosslinking state of the EVA encapsulant. With measurement times below one second per analysis point, the method is suitable for real-time, in-line quality control. Using a self-referencing data evaluation approach, the method could be designed to be widely immune to real-world effects, including different sample reflectivity and instrument drifts. Involving the reaction kinetics of the curing reaction, the Raman data can be converted into crosslinking readings that equal the traditional, Soxhlet-derived gel content values. The method has been successfully validated for bare foils, glass–backsheet and glass–glass modules with three different EVA types and deployed in-line in a commercial PV module manufacturing line. Using Raman spectroscopy, it is thus possible to determine the degree of crosslinking of the EVA encapsulant inside assembled modules in-line and with high accuracy, even on moving modules.

Since the beginning of PV module production, Soxhlet extraction has been the standard method for the determination of the gel content and the resulting calculation of the degree of crosslinking of the most common PV encapsulant ethylene vinyl acetate (EVA). While the method is deemed well established and several pertinent ASTM and ISO standards exist, in practise the actual procedures used in – and trusted by – both industry and R&D institutions vary substantially. To evaluate the reliability of the methods and the comparability of the results, a round-robin test involving seven independent European laboratories – one industrial PV module manufacturer and six R&D facilities – was conducted. The measurements were performed using homogenous, anonymized sample sets, each comprising five differently crosslinked EVA foils. The analysis showed that results obtained for the same samples may deviate significantly, but also that very different analytical procedures can yield comparable values. In a systematic study, the impact of various key parameters of the analytical process (extraction time and solvent, drying conditions, sample size and weight etc.) was investigated. Based on these findings, deviations observed in the round-robin study could be linked to their origins and the main pitfalls were identified. In conclusion, a suggestion for an optimised standard procedure was derived to ensure comparable results at all laboratories.

The following paper will sketch a novel method of how to avoid lead in the module and at the same time enhance the module's efficiency with Light Capturing Ribbons (LCR). Additionally, the new process will show a way to reduce the silver content of crystalline PV modules. The key idea is the application of conductive adhesives. The main result of the project was to prove the ageing behaviour compared to modules from standard production and to show the benefit of LCRs. This method of producing PV modules can help to reduce the depletion of resources to ban toxic lead from mono- and multi-crystalline PV modules.

This paper presents an approach enabling localization and identification of foreign bodies in polymer materials applying a combined approach of x-ray imaging, imaging microscopy, optical coherence tomography and Raman imaging spectroscopy. The reliable detection of even small foreign bodies in polymer materials and parts designated for use in semiconductor manufacturing and processing machines is essential. Foreign bodies can in particular be metals, burnt particles of the polymer of the work piece, or intact or degenerated foreign polymers. In either case, all surfaces of e.g. a handling equipment that get in contact with the semiconductor material or process solutions have to be free of foreign bodies to ensure the integrity of the manufacturing process. Size, localization and material of the foreign body are main parameters that decide if a work piece has to be rejected. Current inspection systems may enable the localization of the foreign body, but are not capable of identifying the material and structure of the foreign body; many components with inclusions are therefore rejected as a precaution. This work aims towards the development of a combined sensor approach as part of an automatic quality assurance procedure which can be integrated in the fabrication process. X-ray imaging is used to identify metal foreign bodies. Imaging microscopy is used to detect foreign bodies on the surface of the polymer parts. Optical coherence tomography is used to measure the three-dimensional position and size of the foreign bodies. Raman imaging spectroscopy is used to identify the composition of the foreign bodies if they are located on the surface.

A total of 16 analytical methods, spanning from classical solvent extraction over different thermo-analytic and mechanical approaches to acoustic and optical spectroscopy, have been evaluated as to their ability to determine the crosslinking state of ethylene vinyl acetate (EVA), the prevailing encapsulant for photovoltaics applications. The key objective of this work was to create a systematic and comprehensive comparison, using a unified set of traceable test samples covering the full range of realistically occurring degrees of EVA crosslinking. A majority number of these tested methods proved fundamentally suitable for detecting changes in the polymer properties during crosslinking based on the effect e.g. its mechanical properties or its crystallinity. Interestingly, when investigated in detail, most of the methods showed mutually different dependencies on the lamination time, indicating a complex range of effects of the chemical crosslinking on the properties and behaviour of the material. Furthermore, Raman spectroscopy could be identified as a potential new method for measuring the degree of crosslinking in-line in the PV module manufacturing process, thus providing an interesting approach for improving process control in PV module processing.

This work analyses samples of the widely used encapsulant of photovoltaics modules, ethylene vinyl acetate (EVA). The samples were cross-linked using a lamination technique for different curing times (0 - 20 minutes). The cross-linking characterization is done by determinating the material dispersion with the aid of a combined temporal- and spectral domain white-light interferometer. With the proposed technique it was possible to discriminate the differences in crosslinking for the given curing times. One important feature of this approach is the possibility to perform space resolved measurements of the crosslinking state with μm-resolution. Furthermore the paper discusses the mathematical analysis and processing of measurement data and shows a prototype solution for the fast and automated data acquisition for industrial application.

With a strong industrial trend towards using thin silicon in semiconductor devices, process legacy-induced stresses are matter of increasing practical importance. A key problem here is a lack of suitable metrology equipment for measuring inherent substrate material stresses in the manufacturing line. To overcome this, the use of Raman microspectrometry as a tool for measuring stress levels and distributions quantitatively on entire productive wafers was researched. Combining model cases, theoretical considerations and real-world samples, it could be shown that Raman can provide the necessary analytical accuracy and reliability, allowing to relate ensuing stress states e.g. to different wafer thinning process parameters.

Snail tracks are discolorations of the silver fingers on solar cells. We present a measurement system that can detect snail tracks. Their origin is unknown, but they are thought to be linked to micro cracks in the solar cell. Regions with micro cracks on a photovoltaic module were identified using electroluminescence measurements. Based on the electroluminescence data the faulty regions were mapped with a system that uses a combination of Raman and fluorescence spectroscopy. Our results show that our measurement system is a powerful tool for detecting snail tracks.

A new kind of calorimeter has been developed at Austrian Aerospace to measure specific material parameters needed for the analysis of thermal vacuum insulation. A detailed description of the measuring device and the measurement results will be given in this paper. This calorimeter facility allows to measure the heat flow through the insulation under vacuum conditions in a wide temperature range from liquid nitrogen to ambient. Both boundary temperatures can be chosen within this range. Furthermore the insulation can be characterized at high vacuum or under degraded vacuum, the latter is simulated by using helium or nitrogen gas. The mechanisms of heat transfer have been investigated, namely infrared radiation between the reflective layers of the insulation and conduction through the interleaving spacer material. A mathematical description of the heat flow through the insulation has been derived. Based on this, the heat flow for a typical insulation material has been calculated by finite element analysis by use of the sotware tool Ansys®. Such a transient calculation is needed to determine the time to reach thermal equilibrium, which is mandatory for a proper interpretation and evaluation of the measurement. The new insulation measurement results combined with the proposed type of analysis can be applied to better understand the thermal behavior of any kind of cryogenic system.