Developed by the German institute Fraunhofer ISE, the cell is manufactured using a metallization based on a plating process.The device was built with nickel/copper/silver galvanic contacts instead of the common silver ones.The TOPCon solar cell with nickel/copper/silver contacts under the microscope.Researchers at the Fraunhofer Institute for Solar Energy Systems ISE in Germany have been trying for several years to reduce the use of silver - one of the main concerns of the photovoltaic industry - in the metallization of TOPCon solar cells, for which they rely on smaller amounts of the precious metal is crucial to reduce manufacturing costs and gain more market share.Recently, a group of scientists from the German institute used galvanic nickel (Ni), copper (Cu) and silver (Ag) based contacts instead of the usual silver contacts to fabricate an n-type bifacial TOPCon cell which is claimed to , achieves higher efficiency than its counterparts with printed silver contacts, while reducing silver consumption by 90%."Even in industrial production, this galvanic metallization allows significant silver savings without having to compromise efficiency," says researcher Sven Kluska.Designed for screen-printed metallization, the cell was fabricated with an industrial-grade boron emitter on the textured front face and passivated by an aluminum oxide/silicon nitride (AlOx/SiNx) cell.The back face was made with a TOPCon layer with a tunneled oxide and a highly doped n-type poly-Si layer that is covered by a SiNx layer."The metallization process combines two steps of electroplating a single side of a Ni/Cu/Ag stack subsequently on each side," said the scientists referring to the metallization technique used."The Ni and Cu were supplied by Atotech Group, while the Ag electrolyte is identical to the one presented by Grübel."The back face of the TOPCon is initially plated using a hydrofluoric acid (HF) pretreatment process designed to remove native and laser-induced oxide layers within the laser contact opening (LCO).In a second step, a Ni-Cu stack is deposited by light-induced plating (LIP) and finished with an Ag dip coating.The performance of the plated cell, which has a total area of ​​268 cm2, was compared to that of a similar device that underwent screen-printed metallization.The device achieved a power conversion efficiency of 23.84%, an open circuit voltage of 709 mV, a short circuit current of 40.9 mA cm-2, and a fill factor of 82.2%.The screen-printed cell showed an efficiency of 23.46%, an open circuit voltage of 708 mV, a short circuit current of 40.4 mA cm-2 and a fill factor of 82.0%.By reducing the width of the LCO and adapting the number of fingers, the plated contacts benefit from narrower contact widths, down to 5.5 μm, allowing a short-circuit current gain of almost 0.5 mA/cm2, academics explained.“There was no indication that the width of the LCO affected the contact adhesion.Optimization of the HF pretreatment before the coating process showed an improvement in the resistivity of the contacts that allowed the fill factor to stabilize above 82% despite the fact that the contact geometries were smaller than those of the silk-screened references. .”The cell and the corresponding fabrication process are described in the article “Progress of plated metallization for industrial bifacial TOPCon silicon solar cells, published” in Progress in Photovoltaics."Plating metallization appears to be a suitable candidate for metallizing i-TOPCon solar cells with high efficiencies that exceed the screen-printed reference metallization," the scientists conclude.This content is copyrighted and may not be reused.If you want to cooperate with us and want to reuse some of our content, please contact: editors@pv-magazine.com.See our rules for commenting on articles here.Your email address will not be published.Required fields are marked with *Save my name, email, and website in this browser for the next time I comment.Receive an email with 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