The silicon solar panel market has somewhat settled into uniformity. After decades of R&D, manufacturers determined that PERC (passivated emitter rear contact) technology would be the foundational building block to all silicon solar panels. To improve beyond that central design, manufacturers can expand into either HJT (heterojunction technology) or TOPCon (tunnel oxide passivated contact). HJT’s more complex formula that adds amorphous silicon thin film into the mix has led most of the industry to take the TOPCon path, which only requires adding one oxide layer to PERC cells.
It’s difficult to stand apart in the crowded TOPCon market, so it’s only natural for patent infringement cries to be heard. While patent claims are common in every industry, these TOPCon patent battles shouldn’t be ignored as everyday business dealings. Who owns what solar panel process could reshape the domestic manufacturing landscape and has already caused companies to pivot in this unstable market.
TOPCon was introduced to the industry in 2013 by the Fraunhofer Institute for Solar Energy Systems in Germany and has been used by mainstream Chinese manufacturers since at least 2019 before becoming globally dominant in the last two years. Testing lab Kiwa PVEL assesses hundreds of solar panels for its annual PV Module Reliability Scorecard and found 2023 to be TOPCon’s breakthrough moment. Just one TOPCon module was submitted for testing in 2022 before jumping to 37 modules in 2023 — 160 TOPCon models were tested in 2024.
Maxeon was the first to dive into TOPCon patent infringement claims, filing separately against Canadian Solar and both REC and Qcells earlier this year. Maxeon holds three patents related to TOPCon technology, which were initially granted to SunPower and assigned to Maxeon in 2022.
“Maxeon has a strong heritage in developing solar cell technology, leading the development and commercialization of tunnel oxide passivated contacts,” said Marc Robinson, associate general counsel for Maxeon. “Years before the moniker ‘TOPCon’ started to be used in the industry to describe a tunnel oxide passivated contact-based solar cell, our scientists and engineers had developed several ways to implement TOPCon technology into both back-contact and front-contact solar cells.”
Then came Trina Solar’s filings, first against Runergy and Adani, before also claiming patent infringement against Canadian Solar. Trina escalated things by requesting the U.S. International Trade Commission complete investigations of the three companies under Sec. 337 of the Tariff Act of 1930, which would direct U.S. Customs to stop infringing imports from entering the United States. Trina was only able to file a Sec. 337 investigation request because it was considered a U.S. manufacturer that needed protection, although in November, Trina sold its Texas manufacturing plant to FREYR.
A slide from a recent First Solar earnings report, illustrating the various patent challenges in the solar industry.
But that’s not all — a non-silicon solar panel manufacturer is also getting into the silicon patent battle. First Solar, which makes thin-film solar panels that don’t use silicon, holds TOPCon patents too. America’s largest solar panel manufacturer secured the patents through its 2013 acquisition of TetraSun, a silicon cell startup. First Solar said it still retains the TOPCon-related patents through 2030 and is investigating several silicon solar manufacturers for potential infringement. The company has yet to officially file any complaints against its fellow U.S. manufacturers, but First Solar will go after the dominant silicon technology if it feels it has merit.
These threats are having direct effects on U.S. solar panel market entrants. New manufacturer Solarix said it will make HJT panels in Virginia to avoid stepping on TOPCon landmines.
“There are many variations of TOPCon that have been patented by many companies. We knew at some point there was going to be some TOPCon patent infringement [allegations],” said Carlos Class, Solarix CEO. “These companies that were developing their manufacturing lines here to use TOPCon in their modules, now they’re putting a moratorium in their 2025 production plans for domestic content.”
In November, Toyo and VSUN announced plans to set up solar panel assembly operations in Houston. A few weeks later, JinkoSolar filed TOPCon patent infringement claims against the two companies and their affiliates. Construction plans are continuing, but a positive infringement finding could halt their domestic production. The same can be said for any of the companies battling things out. A 2020 patent infringement suit between Solaria and Canadian Solar was eventually settled with Canadian Solar prevented from selling shingled solar panels in the U.S. market for seven years. Whether the long list of U.S. manufacturing hopefuls get off the ground could come down to who owns which TOPCon patent.
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