Categories
Scientists in Turkey claim to have developed a nickel-based TOPCon solar cell with a minimal silver content and almost the same efficiency as fully silver metallized counterparts. The device uses a new nickel contact method that requires a trace of silver of only 0.5 mg/W.
A group of researchers at the Middle East Technical University‘s Odtu-Gunam research institute in Turkey claims to have fabricated a TOPCon solar cell with a nickel (Ni) contact and significantly lower silver (Ag) content, with the device achieving almost the same efficiency as TOPCon devices produced via full silver metallization.
“Silver scarcity is a growing concern as solar manufacturing’s appetite for this precious metal surges,” the research’s corresponding author, Veysel Unsur, told pv magazine. “Our team at Odtu-Gunam and Necmettin Erbakan University have tackled this challenge by pioneering a new nickel-based contact method that uses just a trace of silver under 0.5 mg per watt, a tiny fraction of the around 13–20 mg/W used in standard silver contacts.”
“Impressively, our n-TOPCon silicon solar cells reached 23.66% efficiency, virtually on par with the 23.71% efficiency achieved by traditional all-silver contacts,” Unsur went on to say. “By dramatically cutting reliance on costly silver while maintaining performance, this innovation could significantly reduce costs and enable more sustainable, scalable solar cell production.”
For the metallization process, the research team used different four types of Ag-doped Ni metal pastes and a reference product based on aluminum (Al) and Ag provided by German specialist Heraeus. The cells were based on M10 182 mm x 182 mm n-type wafers and featured a tunnel oxide layer of silicon monoxide (SiOX) less than 2 nm thick and an n-doped polysilicon layer, serving as a passivating carrier-selective contact.
The devices also relied on amorphous hydrogenated silicon nitride (a-SiNx) layers, which the scientists said are key to providing hydrogenation to passivate dangling bonds at the Si/SiOX interface. Oxides were used to enable the glass frit to effectively etch the antireflective coating (ARC) and to form a passivating interlayer that improves the overall contact resistance. A nickel oxide (NiO) layer was applied to increase the adhesion and stability of the residual glass layer.
Tested under standard illumination conditions, the cell achieved a power conversion efficiency of 23.66%, an open-circuit voltage of 701.1 mV, a short-circuit current of 41.5 mA/m2, and a fill factor of 81.8%. By way of comparison, the cell with full silver metallization reached an efficiency of 23.71%, an open-circuit voltage of 702.0 mV, a short-circuit current of 41.1 mA/m2, and a fill factor of 81.9%.
“The strategic inclusion of a modest 4 % silver on nickel particles, combined with a re-engineered glass frit, enhances the conductivity and
adhesion of contacts while facilitating the effective selectivity of the carriers,” the scientists emphasized. “The comprehensive analysis confirmed that this novel approach maintains high efficiency comparable to traditional silver contacts.”
adhesion of contacts while facilitating the effective selectivity of the carriers,” the scientists emphasized. “The comprehensive analysis confirmed that this novel approach maintains high efficiency comparable to traditional silver contacts.”
Their findings are available in the paper “Screen printed Ag-doped nickel metallization for industrial n-TOPCon silicon solar cells,” which was recently published in Solar Energy Materials and Solar Cells.