Scientists from the University of New South Wales (UNSW) and Canadian Solar have studied the degradation of industrial TOPCon solar cells under accelerated damp heat test (DH85) conditions, consisting of 85°C and 85% relative humidity.
Their research, titled Unveiling the origin of metal contact failures in TOPCon solar cells through accelerated damp-heat testing, highlights the vulnerability of these solar cells to contact corrosion. It emphasises the electrochemical reactivity of metallisation as a potential risk to long-term operation.
Lead researcher Bram Hoex explained to pv magazine: “This study provides crucial insights into TOPCon cell degradation mechanisms, essential for optimising performance and enhancing the long-term reliability of these modules.”
The research team expanded on their earlier work by introducing two types of sodium-containing salts—sodium bicarbonate (NaHCO3) and sodium chloride (NaCl)—to observe differences in chemical reactions.
Hoex stated, “This improved understanding of the underlying chemistry explaining the degradation is key to further improving the stability of TOPCon.”
The study also revealed three new failure modes for TOPCon modules that were not found in PERC panels.
Hoex noted, “We expected polyolefin elastomer (POE) to perform well, but we identified that some POEs performed very poorly due to different additives reacting with soldering flux and metallisation, resulting in contact corrosion.”
Results showed a significant difference in sensitivity between the front and rear of the TOPCon cells when exposed to NaHCO3 and NaCl.
While NaCl exposure caused a dramatic 92% reduction in power conversion efficiency, NaHCO3 resulted in a 5% reduction. The research concluded that metal contacts in TOPCon cells are susceptible to ion-level contaminants, affecting long-term stability.
The study was published in Solar Energy Materials and Solar Cells and offers insights into improving the reliability of TOPCon solar cells in real-world applications.
