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Low-temperature interconnection processes for high-efficiency PV cells will be a key R&D topic in the coming years. In reality, to avoid significant deterioration of the surface passivation, the metallization and interconnection processes of silicon heterojunction (SHJ) cells are limited to temperatures below 200°C; tandem cells with a perovskite subcell demand an even greater reduction in process temperature, namely below 130°C. Moreover, to ensure the sustainability of PV production on a TW scale, the use of scarce materials, especially silver, needs to be reduced, as 10% of the world's supply was already dedicated to PV in 2020. This paper addresses the results obtained in terms of reducing the silver consumption in interconnection technology based on electrical conductive adhesive (ECA) and Pb-free ribbons. The first demonstration of stencil-printing-based ECA deposition with an improved accuracy using equipment from Mondragon Assembly is reported. This equipment allows a minimal amount of ECA deposition while maintaining highly reproducible results, as demonstrated through the fabrication of 400 glass-glass modules and the validation of process reliability. This paves the way towards creating Si/perovskite tandems that involve ECA curing at temperatures below 130°C with sufficient adhesion (> 0.8N/mm) of the ribbon to the cell, as well as offering a means to consistently reduce Ag usage. Furthermore, improvements to the Mondragon Assembly stringer to handle next-generation cells are outlined. [ABSTRACT FROM AUTHOR]

This article reports on the 11th Workshop on Metallization and Interconnection for Crystalline Silicon Solar Cells, which took place in May 2023 in Neuchâtel, Switzerland. An important observation at the workshop was that, while screen printing is still dominating metallization, alternative pastes with increasing Cu content are starting to be implemented in the industry in response to the need to decrease cost and improve sustainability. Compared to previous workshops, interconnection topics were more prevalent in this edition because of the need for interconnection solutions that work at lower temperatures, as is needed for emerging solar cell technologies. Electrically conductive adhesives (ECA) have gained in importance in this respect. Understanding of reliability aspects and insight into proper characterization of ECAs are increasing, yet the challenge is here is to substantially further reduce cost and silver content. [ABSTRACT FROM AUTHOR]

Recent research has shown that bifacial PV modules with a glass/glass packaging are prone to different PID mechanisms occurring simultaneously on the front and the rear side of the solar cell. With this in mind, researchers investigating the impact of PID on each side of the bifacial solar cell separately apply PID stress to one side of bifacial PV modules according to stress method (b) as described in the IEC TS 62804‐1, that is, contacting the surface with a conductive electrode. Yet, in this paper, we show that such practice of PID testing might result in an unintended development of an electric field between the environmental chamber and the nonstressed side of the solar cell. Through our experimental study, we reveal that this electric field results in unintended bifacial PID stress of bifacial solar cells, which goes along with misleading interpretations of the evolving PID mechanisms and susceptibility of bifacial PV modules. Next to the methodology concerns, we discuss three possible solutions to prevent such unintended PID mechanisms from occurring. [ABSTRACT FROM AUTHOR]

The combination of increasing operational voltages beyond 1000 V in photovoltaic (PV) installations and the emergence of new PV technologies requires a critical assessment of the susceptibility to potential-induced degradation (PID). Since this failure mode can trigger significant and rapid power losses, it is considered among the most critical failure modes with a high financial impact. Insights in the physical mechanism of the performance loss and its driving factors are critical to develop adapted characterization methods and mitigation solutions. PID in p-type solar cells is triggered by sodium (Na) that diffuses into stacking faults of the silicon lattice, causing shunt paths through the pn-junction. In addition, it is hypothesised that for bifacial p -PERC solar cells positive charges, such as Na+, accumulate in/on the negatively charged AlO x rear passivation layer due to the potential difference between the glass and the rear cell surface. This significantly increases surface recombination. However, the degradation behaviour observed in bifacial monocrystalline p -PERC solar cells under PID stress from both sides (bifacial PID stress) does not match with just one of the degradation mechanisms. A comprehensive test matrix was carried out to understand the physical origin of PID in front emitter bifacial p -PERC solar cells in a glass/glass packaging. The results show that bifacial p -PERC solar cells under bifacial PID stress suffer from both shunting of the pn-junction and increased surface recombination at their rear side. Hereby, we prove that the glass/glass packaging in combination with bifacial solar cells can significantly increase the severity of PID. Bifacial PID of bifacial p -PERC solar cells when using a glass/glass module configuration: PID-s occurring at the front/emitter side and PID-p occurring at the rear side of the solar cell. Image 1 • Front junction bifacial p -PERC solar cells suffer from both PID-s and PID-p. • Glass/glass packaging renders bifacial solar module types more sensitive to PID. • PID-s and PID-p can be easily distinguished by IV and EQE measurements. [ABSTRACT FROM AUTHOR]