Recent scientific investigations have highlighted significant reliability hurdles for tunnel oxide passivated contact (TOPCon) solar modules, revealing new degradation pathways under environmental stress. Research from the University of New South Wales and the National Renewable Energy Laboratory indicates that these modules may experience power losses between 6% and 16% during extended damp-heat exposure, largely influenced by the choice of encapsulants. While cell-level defects are reportedly stabilizing across the industry, experts caution that the rapid transition to TOPCon technology has outpaced long-term technical validation, potentially undermining performance warranties in diverse climates.
The study from the University of New South Wales (UNSW), recently published in the journal *Solar Energy Materials and Solar Cells*, specifically examined how different encapsulation materials affect TOPCon performance. After subjecting modules to 2,000 hours of humid, damp-heat stress testing, researchers found that those using polyolefin elastomer (POE) on both sides demonstrated the highest stability, with degradation limited to approximately 8%. In contrast, modules utilizing ethylene vinyl acetate (EVA) on the rear and EPE on the front saw power losses climb to 16%.
The researchers identified a specific degradation mechanism triggered by magnesium additives within the EVA material. Under damp-heat conditions, these additives hydrate to create an alkaline micro-environment, which facilitates moisture ingress into the polysilicon layers of the solar module. The findings suggest that using POE on the rear side of the module offers significantly better protection against humidity-driven power loss, particularly in glass-backsheet configurations.
Further complications involve ultraviolet-induced degradation (UVID). A separate paper from the National Renewable Energy Laboratory (NREL) explored the “metastability” of TOPCon modules. The study found that modules can continue to degrade while stored in the dark but show rapid recovery once exposed to sunlight. This fluctuating performance makes it exceptionally difficult for technicians to accurately quantify the long-term impact of UVID on solar cell efficiency, with observed variance in degradation and recovery rates ranging from +6% to -70%.
These findings align with earlier warnings from the Fraunhofer ISE in Germany, where scientists labeled TOPCon degradation rates as “critical.” The institute suggested that the industry’s rush to mass-produce TOPCon products has bypassed essential technical qualifications. This rapid deployment means many modules currently on the market may not meet the 25-to-30-year lifespans promised by their manufacturers.
Despite these concerns, there are signs of industrial progress. A recent quality report from Kiwa PI Berlin noted that cell-related defects in TOPCon production have begun to decline, reaching levels comparable to the older PERC technology. This improvement is attributed to more refined cell-level designs and growing manufacturing expertise.
However, the report also highlighted significant regional disparities in quality. Facilities in the United States currently show higher defect rates compared to established manufacturing hubs in Vietnam and Indonesia, where experienced Chinese manufacturers maintain more stable operations. Experts suggest that the variation in quality is often linked to supply chain disruptions and the learning curve of new production lines. Consequently, industry analysts are urging developers and investors to demand greater transparency from suppliers and to implement rigorous quality assurance protocols to mitigate the financial risks associated with these emerging degradation issues.