A new design for the flow of electricity through solar cells that could cut module costs as much as 10 percent has been developed by GT Advanced Technologies.
GT’s Merlin metallization process replaces the three thick strips of silver that run through modules, called busbars, with thin lines of silver scattered through the cells. The silver lines, called fingers, function as the cell’s wiring, channeling electrons released when sunlight hits the cell’s semiconductor material into the electrical system.
GT said Merlin can be retrofitted into existing cell manufacturing lines’ screen printers. An additional attachment tool would insert a coated copper overlay with a tab at the cell’s edge. Electrons flow through the Merlin architecture from the silver fingers into the copper overlay and to the tab.
“The concept seems to have potential, because it attacks some critical areas in the manufacturing process and module design,” said GTM Research Lead Upstream Solar Analyst Shyam Mehta.
The solar industry’s drive to reduce silver use is a topic that merited its own section in GTM Research’s recent report on crystalline silicon technology, authored by Mehta and Andrew M. Gabor. “The cost of the silver paste ﬁngers and busbars on the front and back of standard solar cells represents the largest cost in the cell after the wafer,” they wrote.
In the new design, rather than flowing through the three busbar channels, electrons pass through the twenty copper channels in the overlay through widened interconnections on the tabs that serve to streamline the flow.
Each cell would be 0.7 percent more efficient than standard designs because the narrower, thinner silver fingers expose slightly more of the cell’s surface to sunlight. In addition, the overlay reduces resistance and recaptures reflected incident light, according to GT Communications Director Jeff Nestel-Patt.
The 80 percent reduction in silver also makes the modules significantly lighter in weight, Nestel-Patt said. That would reduce shipping costs and make for easier handling and installation. He added that the tabs also make the module more flexible and durable, because the busbars’ three failure points are replaced by the tabs’ twenty interconnectio
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