Scientists at the University of New South Wales have introduced a groundbreaking method to protect TOPCon solar cells by applying a 1 µm copper plating layer to the front silver grid. This innovative approach aims to significantly reduce corrosion, enhancing the reliability and efficiency of these cells under challenging conditions.
Understanding the Challenge: Corrosion in Solar Cells
The solar industry faces a significant challenge in extending the lifespan and performance of TOPCon (tunnel oxide passivated contact) solar cells. These cells are particularly susceptible to corrosion, especially when exposed to contaminants and damp conditions. This degradation leads to a decline in efficiency and increased maintenance costs, ultimately undermining the long-term profitability of solar installations.
The Copper Coating Solution
To address this issue, researchers from the University of New South Wales have developed a novel copper plating technique. The process involves applying a 1 µm layer of copper to the front silver grid of TOPCon solar cells. This copper coating acts as a protective barrier, significantly reducing the cells’ susceptibility to corrosion.
Improved Durability and Reliability
The study, led by Bram Hoex, demonstrated that the copper-coated cells showed a marked improvement in durability and reliability compared to their unprotected counterparts. After six hours of damp heat testing, unprotected cells experienced over 80% relative efficiency degradation. In contrast, the copper-plated cells retained over 88.5% of their initial efficiency.
“Our work specifically addresses a key challenge: the sensitivity of TOPCon cells to corrosion, particularly on the front metallization,” Hoex stated. “We introduced a 1 µm Cu plating layer on the front silver grid, creating a protective barrier that significantly reduces corrosion susceptibility.”
Technological Process
The plating process was carried out using a Conifer plating tool. The researchers submerged the cells in a plating solution containing copper sulfate (CuSO4) while applying bias-assisted light-induced plating (LIP) with a constant current of around 150 mA and continuous illumination.
This method not only enhanced the cells’ performance but also improved their soldering process by filling voids in the silver contacts, creating a denser and more robust interface.
Quantitative Results
The experiments revealed that the plated-Cu contacts achieved an initial efficiency improvement of around 0.39% relative (rel). Transfer length method (TLM) measurements also showed a tenfold increase in contact resistivity for unprotected cells after just 0.5 hours of testing, while the copper-plated cells maintained lower resistivity levels over extended periods.
Material Science Insights
Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analysis confirmed that the copper plating filled voids in the silver contact, creating a more reliable interface that prevents contaminant penetration and reduces parasitic recombination.
“Considering the results of this accelerated test, we conclude that the plated-Cu layer can effectively alleviate NaCl-induced degradation under damp heat conditions and highly improve device stability,” the scientists concluded.
Broader Implications
The findings have significant implications for the solar industry, particularly in terms of reducing silver consumption and lowering the levelized cost of electricity (LCOE). By enhancing the durability and reliability of TOPCon cells, the industry can achieve more cost-effective and sustainable solar solutions.
Conclusion
The copper plating technique developed by researchers at the University of New South Wales represents a significant step forward in enhancing the durability and reliability of TOPCon solar cells. By effectively mitigating corrosion and contamination-induced degradation, this innovation could lead to more efficient and cost-effective solar solutions.
“The contact resistivity of NaCl-exposed bare cells was already one to two orders of magnitude higher than that of plated cells after just two hours of testing, explaining most of the loss in fill factor,” the researchers emphasized.
To learn more about this exciting development and its implications for the solar industry, delve into the full study “Alleviating contaminant-induced degradation of TOPCon solar cells with copper plating,” published in Solar Energy Materials and Solar Cells.
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