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The world record is achieved using industrial-scale equipment for interconnection and encapsulation of rear-contact cells. This equipment is provided by the Dutch equipment builder Eurotron. The Dutch solar cell manufacturer Solland Solar will be the first to use the world-record technology in commercial production, later this year. The research and development has been financed by the European Commission within the project CrystalClear and by the Dutch government through SenterNovem.
ECN has developed the new module design and manufacturing process based on a solar cell design with all contacts on the rear. ECN’s rear-contact technology is based on metallization wrap-through (MWT) solar cells which are interconnected in modules using conductive adhesives and a patterned conductive foil. This has similarities with surface mounting of electronic components on a printed circuit board. In MWT cells the front electrode is “wrapped through” small vias in the cell, so that it can be contacted at the rear, in parallel with the rear-side electrode.
The MWT technology has several important benefits. First, it significantly improves the module conversion efficiency. Metal strips are used in standard modules to connect the front of one cell with the rear of a neighboring cell. These strips block part of the incoming light, and require spaces between the cells, leading to a lower packing density of cells and thus to a lower module efficiency. In addition, the use of a patterned conductive foil results in lower resistance losses than for strips, also leading to higher module efficiencies. The second benefit of MWT is that very thin and fragile solar cells can be used. The world record module was built with 36 cells of 120 micron thickness only, much thinner than the 180-200 micron as practiced by industry. This module was made on the industrial-scale equipment without any cell breakage, demonstrating the potential of this technology for cost reduction. This is made possible by simplifying the module manufacturing process. The MWT technology uses pick-and-place cell handling in combination with conductive adhesives. This gives a minimum of mechanical and thermal impact and stress throughout the manufacturing process. The combination of higher performance and more efficient manufacturing leads to lower costs of the modules and of solar electricity generation.
The modules made with this technology are already for years being tested for reliability. Outdoor and climate chamber tests show excellent performance and normal certification tests have already been passed. The final step is to achieve full IEC certification of the modules which is expected to be completed by the end of this year.