Researchers from the University of New South Wales (UNSW) and Longi have discovered that the silicon nitride (SiNx) layers used in TOPCon cell rear-sides are prone to chemical degradation from sodium contaminants, leading to significant open-circuit voltage losses and reduced cell efficiency.
The team’s study, published in Solar Energy Materials and Solar Cells, exposed TOPCon solar cells to various sodium-related salts under damp-heat testing, a rapid testing method that simulates extreme humidity and heat conditions. The test revealed that two sodium contaminants, CH3COONa and sodium chloride (NaCl), caused significant performance losses, with a 16% loss in efficiency and 4.8% relative decrease in open-circuit voltage.
The researchers found that the rear-side SiNx layer was particularly vulnerable to chemical reactions and surface degradation caused by sodium-based salts, leading to reduced performance and efficiency. The study suggested that a 10nm aluminum oxide (AlOx) barrier layer deposited on the cell front side via atomic layer deposition (ALD) can mitigate the degradation mechanisms and reduce performance losses.
The team’s findings highlighted the need for improved strategies to address the vulnerability of TOPCon solar cells to sodium-induced degradation, which can significantly impact their performance and reliability. The researchers proposed the integration of the AlOx layer in commercial production to enhance the long-term reliability of TOPCon solar cells under harsh environmental conditions.
Future research aims to better integrate the AlOx layer in commercial production and analyze long-term degradation behaviors under real-world conditions. The study is significant, as it reveals the previously overlooked vulnerability of TOPCon solar cells to sodium-induced degradation and provides a potential solution to address this issue, ultimately enhancing the performance and reliability of solar panels.