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The paper addresses the need to simplify the comparison between different climatic conditions. Therefore, the concept of Mission Profiles is introduced to PV. Mission Profiles are a set of climatic stresses compiled to allow direct comparisons such as temperature, humidity, and UV exposure. The use-case in this paper is a comparison of a temperate with a hot climate. The results show that temperature driven processes are highly accelerated for the hot climate, whereas processes that involve humidity may lead to a similar annual degradation. The impact of light, particularly UV, is even more complex. UV triggered reaction processes can be photon absorption triggered and accelerated by temperature. However, for most observed interactions and material changes UV light goes in conjunction with moisture (H2O) for the chemical reaction and is accelerated by temperature. Calculating the impact of temperature and UV is possible. However, the impact of moisture is almost impossible as it requires the knowledge of the local microclimate. Only a “worst-case” scenario can be assumed while using ambient relative humidity for most events of the day, that, however, do typically not include condensation. With the introduction of Mission Profiles, it should be possible to assess stress more easily for particular sites in general. Differences in mounting such as open rack compared to e.g., BiPV can also better addressed, however, with some assumption to define the microclimate (e.g., exclude rear side cooling).

Within this work the impact of contact materials with higher volume resistivity as leaded solder are investigated in terms of comparability of the current conduction through the joint. An approach was developed to experimentally determine the qualitative local current density by magnetic field imaging (MFI) at ribbon-to-ribbon contact samples. The result reveals that the MFI technique on a symmetric sample design allows the evaluation of the current paths in two-dimensional contact areas. Different resistivities of the contact material result in characteristic differences in current distribution through the joint. Low resistive Sn60Pb40-soldererd contacts exhibit localized current injection whereas the tested contact based on electrically conductive adhesives (ECAs) show an extended current flow through the ECA-based contact. A FEM-based simulation model to mimic the used setup was developed and confirmed the results by taking different contact material resistivities into account. For materials with resistivities larger than 1 · 10−3 Ω · cm current injection was found to spread-spatially within the tested contact geometry. Contact material development as well as contact design can benefit from that approach, allowing consumption and material composition optimization. A further advantage is the feasibility of the method to study production failures like inhomogeneous ECA distribution enabling a non-destructive monitoring of process stability and root cause analysis.

It was previously shown that the Laser Enhanced Contact Optimization (LECO) Process is a promising boost for PERC and TOPCon cell manufacturing enhancement. In this contribution, a method is developed to assess the long-term stability of industrial LECO treated PERC cells in a module compound. Therefore, extended accelerated aging tests as well as outdoor measurements were performed on modules comprising LECO treated cells as well as untreated references. It is described, how data can be evaluated to separate typical, known aging and degradation effects from presumable LECO specific effects. The results of this work show that test modules comprising LECO treated cells did not show a different behavior in the accelerated aging or degradation compared to the reference. The same conclusion was found for thermal cycling and damp heat tests, both far in excess of IEC requirements, as well as in a sequential test sequence. In addition, their outdoor performance with local and integral measurements has been evaluated. We can conclude that for the tested PERC cells, aging and degradation effects appeared, but none of them could be attributed to the LECO process. Hence, improvements in the efficiency and/or yield on cell level due to LECO can be translated to the module or even system level considering typical aging and degradation behavior, independently of a prior LECO process.

PV manufacturing has progressed quite a bit in recent years, from handmade products entailing high human-effort-based assembly to fully automated cell and module factory production in just the last decade. Machine-based production offers high reproducibility; nonetheless, it can lack the ability to easily make required production process adjustments. Production windows can be maintained comfortably provided nothing changes; however, if materials change and require more process adjustments, those - no longer appropriate - processes can lead to variable production quality and can therefore cause longterm durability issues. This paper presents a way to evaluate production windows and related field issues using an adapted failure mode and effects analysis (FMEA) approach. Since PV modules are the most important component in terms of longevity and warranties, the focus of Fraunhofer's work has been on module manufacturing. The process, however, can also be applied to cell manufacturing and other steps in the value chain. By means of FMEA methodology, a group of equipment and module manufacturers, along with several interdisciplinary scientists, have analysed possible production issues and their impact on reliability and have determined the important factors for risk, detection and severity. The processes with the highest risk priority numbers (RPNs) are followed up with regard to process variations and a detailed indoor and outdoor test study. In view of the fact that data analytics is gaining importance for process optimization, an example is given to demonstrate how data can help to improve process stability, as well as increase efficiency, reliability and production yield. [ABSTRACT FROM AUTHOR]

According to the International Technology Roadmap for Photovoltaics, passivated emitter and rear solar cells dominate the market in 2021 of up to 80% and are forecast to remain state of the art at least for the next 5 years. Within the production process of solar cells, it is typical to have cells with lower efficiency grades due to variations in manufacturing processes or material defects. Reprocessing such solar cells could save cost due to increased production yield and simultaneously reduced cost for recycling of unusable/unsellable low‐efficiency cells. Herein, the impact of the laser‐enhanced contact optimization (LECO) process on the power output and reliability of solar modules using commercial off‐spec cells of different manufacturers is analyzed. LECO is a downstream process for optimizing metal−semiconductor contacts on finished solar cells. The treatment leads to a significant economic gain due to enhanced cell efficiency (Wp ↑, therefore manufacturing cost per Wp ↓) even of already good solar cells. Herein, the first evaluation of the impact of the LECO process on the cell output power on an industrial scale (>1000 cells) and on module reliability is presented. The results for common short‐term effects like light‐induced degradation and light‐ and elevated temperature‐induced degradation are within expected limits and the durability against, for example, potential‐induced degradation is not changed due to the LECO process. The results further show that cell sorting is crucial for a reliable module and to avoid outliers in terms of unexpected degradation and recovery phenomena of individual cells. [ABSTRACT FROM AUTHOR]

Although electrically conductive adhesives (ECAs) have been around in the PV industry for several years in panels based on conductive backsheets as well as in the so-called shingled or tiled modules, several evolving trends and new technologies are currently converging to bring ECAs firmly into the mainstream spotlight. These include the ongoing move to thinner wafers and larger cell formats, as well as the inevitable increase in market penetration of high-efficiency concepts based on heterojunction (HJT) and silicon--thin-film tandem cell architectures. With mature product offerings now available from several of the leading industrial PV equipment and tool manufacturers, and latest-generation ECAs available from suppliers, this article aims to provide important background information on ECAs, as well as give a brief overview of some of the challenges and cutting-edge developments in ECA-related PV applications. [ABSTRACT FROM AUTHOR]

A single quadrupole mass spectrometer coupled measuring setup was developed for the investigation of the helium transmission rate (HeTR) of SiOx-coated polyethylene terephthalate (PET) barrier films. The setup allows the pressure-less and timeresolved measurements of the helium permeation at transient and steady-state conditions. Whereas standard water vapour transmission rate (WVTR) experiments took extended test times (in the range of several days), HeTR measurements were finished after 1 h. For the material system investigated here, an excellent linear correlation of WVTR and HeTR was proven over two orders of magnitude (regarding WVTR). Experiments with application of different strain loads on the coated films revealed a significant increase of both, HeTR and WVTR. Scanning electron microscope (SEM) measurements evidenced multiple ruptures of the SiOx coating depending on the applied strain and initial thickness of the SiOx layer. Considering virgin barrier films and strain-ruptured barrier films, a good correlation of WVTR and HeTR was shown. [ABSTRACT FROM AUTHOR]

The majority of solar module manufacturers use ethylene-vinyl acetate (EVA) copolymer foils as the encapsulant material for solar cells and thin-film modules. Because EVA needs long processing times for curing, thermoplastic process materials that do not employ chemical cross-linking have been coming more and more into focus in the encapsulation sector This paper takes a look at the mechanical temperature-dependent properties of a variety of such materials. [ABSTRACT FROM AUTHOR]