Adani group firm's petition to challenge First Solar's TOPCon patent rejected by US authorities 

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• USPTO rejects Adani's petition to review First Solar's TOPCon patent
• Similar review requests by JinkoSolar and Canadian Solar also denied
• First Solar sues Adani for patent infringement in Delaware court

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The United States Patent and Trademark Office (USPTO) has rejected a petition filed by an Adani Group firm seeking a review of US-based First Solar’s patent covering TOPCon solar cell technology, according to an order seen by Moneycontrol.

The petition was filed by Mundra Solar, an Adani Group unit, as part of an inter partes review (IPR) process to invalidate First Solar’s TOPCon patents. The USPTO also denied similar review requests filed separately by JinkoSolar and Canadian Solar.

The IPRs were filed in 2025 and declined on November 20, December 11 and December 18, respectively, as per the orders issued by the US patent authority.

In its ruling, the USPTO said the petitioners had failed to meet the threshold required to initiate a review. “Pursuant to 35 U.S.C. § 314(a), after review of the merits, the petitioner has failed to show a reasonable likelihood of prevailing with respect to at least one of the claims challenged in the petition. Accordingly, institution of inter partes review is denied,” the order said.

Mundra Solar had sought a review of First Solar’s US Patent No. 9,666,732, which covers methods of manufacturing TOPCon crystalline silicon photovoltaic solar cells. The patents in question were issued in 2015 and 2017, First Solar said in a statement, adding that they predate the petitions by several years. The company acquired the TOPCon intellectual property through its 2013 acquisition of TetraSun Inc.

TOPCon, or Tunnel Oxide Passivated Contact technology, is an advanced solar cell architecture that improves efficiency compared with traditional PERC technology.

The ruling assumes significance for the Adani Group as Mundra Solar scales its export-focused solar manufacturing business, which is heavily reliant on the US market. The company operates a 2 GW facility that manufactures TOPCon modules designed for higher efficiency and improved performance.

The development comes amid an ongoing legal tussle between First Solar and Mundra Solar PV Ltd in the US. First Solar has filed a patent infringement lawsuit in a Delaware court, alleging that an Adani Group entity infringed two patented solar panel manufacturing technologies. The US-based company has sought damages for the alleged infringement, though it has not disclosed the compensation amount claimed.

Mundra Solar PV has reportedly argued in court filings that its manufacturing process differs from First Solar’s patented technology, citing multiple distinctions, including at the heat treatment stage.

As of March 2025, Mundra Solar reported export revenue of Rs 3,880 crore, according to regulatory filings. Its revenue from operations rose to Rs 6,352.6 crore in FY25 from Rs 3,117 crore in FY24, while net profit surged to Rs 1,085 crore from Rs 189 crore over the same period.

Mundra Solar is majority-owned by Adani Green Technology Limited, which held a 51 percent stake as of March 31, 2025. The remaining 49 percent is held by Adani Emerging Businesses Private Limited, classifying Mundra Solar as an associate of that entity.

The Adani Group did not immediately respond to Moneycontrol’s request for comments.