The federal patent office rejected separate challenges from JinkoSolar, Canadian Solar and Mundra Solar to invalidate intellectual property that First Solar claims is fundamental to the manufacturing of crystalline silicon solar cells.
U.S. Patent and Trademark office
Image: Coolcaesar, Wikimedia Commons
The Director of the United States Patent and Trademark Office denied three separate review applications seeking to invalidate patents related to Tunnel Oxide Passivated Contact TOPCon technology held by Frist Solar.  
JinkoSolar and Canadian Solar sought to invalidate U.S. Patent No. 9,130,074 while Mundra Solar challenged U.S. Patent No. 9,666,732. Both patents cover methods of manufacturing solar cells.  
The decision to deny the reviews leaves the patents intact as First Solar pursues infringement litigation in the United States District Court for the District of Delaware. 
First Solar acquired the patents through its purchase of Silicon Valley startup TetraSun in 2013. The company announced intent to license and enforce the portfolio in July 2024.  
The company has since filed lawsuits alleging that competitors are using the patented methods without authorization to produce high-efficiency crystalline silicon modules. 
The manufacturer noted that the patents were issued in 2015 and 2017. First Solar said the rejections are consistent with the “doctrine of settled expectations.” The doctrine is based on the idea that the longer a patent remains in force without being successfully challenged, the more “settled” the owner’s rights become. 
In early 2025, First Solar secured a licensing agreement for the technology with Talon PV, a manufacturer planning a 4 GW cell facility in the United States. Other companies in the crystalline silicon market, including Trina Solar, have also launched their own investigations into potential TOPCon patent breaches as the technology becomes the dominant architecture for the global industry. 
First Solar holds international counterparts to these patents in markets including China, Japan and the European Union. The company indicated it will continue to pursue legal action against manufacturers it believes are infringing on the rights. 
First Solar issued a warning to shareholders and its competitors in November 2024 that alleged that the Longi, Trina Solar, Jinko Solar, JA Solar and Canadian Solar were using First Solar TOPCon patents without a license. 
In another recent solar manufacturing patent dispute, Chinese-Canadian solar module manufacturer Canadian Solar announced a “decisive victory” in the patent litigation proceedings against Singapore-based competitor Maxeon. 
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