As solar technology continues to evolve, TOPCon (Tunnel Oxide Passivated Contact) solar cells are rising as a promising alternative to conventional solar panel technologies. Solar manufacturers such as JinkoSolar and Trina Solar have reported field tests showing TOPCon solar modules outperforming conventional p-type rear contact photovoltaic (PV) modules in monthly power generation. However, alongside these impressive performance results, new concerns have emerged over the reliability and risks associated with TOPCon technology.
Recent findings, notably from the 2024 Kiwa PVEL scorecard, indicate that while TOPCon technology shows potential in improving solar efficiency, it also comes with a higher vulnerability compared to established technologies like PERC (Passivated Emitter and Rear Cell).
The increased risks have raised eyebrows across the solar industry, with researchers, manufacturers, and installers now closely examining the long-term feasibility of this new technology.
What Exactly is the TOPCon Technology?
Before diving into the risks, it's essential to understand what TOPCon technology brings to the table. TOPCon is a solar cell architecture designed to improve efficiency by reducing energy losses. It accomplishes this by inserting a thin tunnel oxide layer between the silicon wafer and metal contact, allowing for better electron flow.
The promise of higher efficiency has spurred interest in TOPCon technology, but it’s not without challenges. As with every advancement in the solar industry, new risks and concerns have arisen, some of which are causing hesitation in the widespread adoption of TOPCon panels.
Kiwa PVEL Scorecard Highlights Risks
One of the key studies shedding light on TOPCon’s vulnerabilities is the latest scorecard from Kiwa PVEL, a renowned testing lab in the solar industry. According to Asier Ukar, managing director of Kiwa PI Berlin, less than 6% of the 388 models tested were top performers across all reliability tests, which include Thermal Cycling (TC), Damp Heat (DH), Mechanical Stress Sequence (MSS), Hail Stress Sequence (HSS), Potential Induced Degradation (PID), and Light-Induced Degradation plus Light and Elevated Temperature Induced Degradation (LID+LETID).
In fact, 66% of the module manufacturers tested experienced at least one failure in the reliability tests. The most concerning finding? The failure rate at the BOM level (Bills of Materials) increased to a staggering 41%, the highest ever recorded. “This year’s results have surprised us,” Ukar stated, emphasizing that PV modules with the same model type can be manufactured using completely different materials, which can significantly impact reliability and performance.
For example, in Thermal Cycling tests, the International Electrotechnical Commission (IEC) typically tests with 200 cycles, while Kiwa PVEL subjects the modules to 600 cycles to simulate the effects of extreme temperature fluctuations. The pass requirement is that the modules degrade less than 2%, and while 84% of the modules passed the test, 11 manufacturers experienced failures. The average degradation rate for PERC and TOPCon modules was 0.6% and 0.7%, respectively, but 5 TOPCon BOMs registered power degradation failures compared to just 1 PERC BOM. These numbers paint a sobering picture for those considering TOPCon as the next big leap forward.
TOPCon’s Susceptibility to Contact Corrosion
Another emerging risk with TOPCon technology is its susceptibility to contact corrosion. Researchers at the University of New South Wales recently published findings that highlight this vulnerability, which poses a significant risk to the longevity of TOPCon cells.
Solar modules, including those using TOPCon technology, are subjected to extreme environmental conditions—ranging from intense sunlight to heavy rain and humidity. Over time, these conditions can lead to contact corrosion, which degrades the module’s performance. This degradation can become a serious issue for consumers who expect their solar systems to perform optimally for 20 to 25 years.
While manufacturers are aware of this risk, the current data suggests that TOPCon cells may degrade more quickly than PERC cells under certain conditions, making durability a primary concern moving forward.
Increased Failure Rates in Key Stress Tests
Kiwa PVEL’s testing procedures go beyond standard industry regulations to simulate real-world conditions. As mentioned, Thermal Cycling tests are performed with 600 cycles instead of the IEC’s standard 200. In another test, Damp Heat, the panels are exposed to 2,000 hours of moist heat (compared to the IEC’s 1,000 hours), simulating long-term exposure to humid conditions.
The results weren’t favorable for TOPCon. 31% of BOMs tested failed the Damp Heat test, with TOPCon showing more vulnerability than PERC. The high failure rate suggests that moisture can accelerate the degradation process in TOPCon cells, a major concern for consumers in humid or tropical climates.
UV-Induced Degradation
Perhaps one of the most concerning findings was related to UV-induced degradation (UVID). During the UVID test, solar modules are exposed to ultraviolet radiation, simulating years of exposure to sunlight. The power loss for TOPCon modules ranged from 0.6% to a staggering 16.6%, a much higher variation than expected.
These results underscore the potential risks of using TOPCon in regions with high UV exposure. While every solar module degrades over time, the wide variation in power loss for TOPCon cells is alarming, particularly for consumers in sunny regions where UV exposure is a daily reality.
What’s Next for TOPCon Technology?
Despite these concerns, many in the industry remain optimistic about TOPCon’s future. It’s widely believed that TOPCon will become the dominant technology in the next five years, but only if the identified risks are addressed. Manufacturers are already working on solutions, including extended-duration tests that simulate longer periods of exposure to environmental stressors like humidity, UV radiation, and temperature fluctuations.
Experts suggest that the solar industry needs to adapt its testing procedures to account for the unique challenges TOPCon introduces. “The good news is that both the tools and the knowledge exist and are at the service of the industry,” Ukar concluded, emphasizing that the industry is well-positioned to mitigate these risks with the right testing frameworks.
Proceed with Caution
TOPCon technology undoubtedly represents an exciting leap forward for solar efficiency, but it comes with its fair share of risks. From increased failure rates to UV degradation, manufacturers and consumers must proceed with caution when considering TOPCon modules for large-scale deployment.
While the industry has the tools to address these challenges, understanding and mitigating the emerging risks will be crucial for the technology’s success. As TOPCon continues to evolve, the solar industry must focus on long-term reliability and performance, ensuring that this promising technology lives up to its potential without compromising quality.
If you're considering TOPCon technology for your next solar project, contact us today for expert guidance on how to navigate its benefits and risks. Our team is here to help you make informed decisions that will maximize your solar investment.
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