In a significant legal setback for the Adani Group’s solar division, the U.S. Patent and Trademark Office (USPTO) officially rejected a series of petitions filed by Mundra Solar PV Ltd (an Adani subsidiary) and other international firms.
As of January 21, 2026, the USPTO Director denied three separate Inter Partes Review (IPR) applications filed by Mundra Solar, JinkoSolar, and Canadian Solar. The companies were seeking to invalidate two key technology patents held by the American firm First Solar related to high-efficiency TOPCon (Tunnel Oxide Passivated Contact) solar cells.
1. The USPTO Decision: “Settled Expectations”
The USPTO’s refusal to review the patents means the legal challenge to invalidate First Solar’s intellectual property has failed at the administrative level.
- Doctrine of Settled Expectations: The USPTO Director cited this doctrine in the denial, noting that First Solar’s patents (issued in 2015 and 2017) have been in force for nearly a decade. The office ruled that the patent holder’s expectation of validity increases over time, making late-stage challenges harder to sustain.
- A “Clean Sweep”: The rejections were issued between November 2025 and December 2025, with the final confirmation of the board’s stance becoming public in late January 2026.
2. Impact on the Delaware Court Case
The USPTO rejection is a major win for First Solar, which currently has an active patent infringement lawsuit against Mundra Solar in the U.S. District Court for the District of Delaware.
- No “Stay” of Litigation: Typically, companies file IPR petitions to pause court cases while the Patent Office re-examines the patents. With the petitions rejected, the Delaware lawsuit will now proceed at full speed toward a jury trial.
- Adani’s Defense: Mundra Solar argues that its manufacturing process is substantially different from First Solar’s—specifically claiming it has eliminated the “heat-treatment” phase central to First Solar’s patents.
- Doctrine of Equivalents: Legal experts warn that even if Adani’s process is technically different, U.S. law allows for infringement if the process achieves “substantially the same function in the same way to yield the same result.”
3. Why the TOPCon Tech Matters
The battle over TOPCon (Tunnel Oxide Passivated Contact) is essentially a battle for the future of the solar market as the industry moves away from older “PERC” technology.
| Aspect | Strategic Importance |
| Market Access | Over 50% of Mundra Solar’s revenue comes from the U.S. market. |
| Tariff Advantage | Indian solar cells are currently exempt from the 50% tariffs placed on Chinese imports, giving Adani a massive competitive edge that this lawsuit now threatens. |
| Financial Stakes | Adani’s solar export business is valued at roughly $1.6 billion annually. |
4. Broader Legal Context (2026)
The patent rejection follows a period of intense legal pressure for the Adani Group in the United States.
- SEC/DOJ Case: In November 2024, the U.S. indicted Gautam and Sagar Adani in a separate $250 million bribery and fraud case. As of February 1, 2026, both have agreed to receive legal notices in that civil fraud case, allowing the matter to proceed without further service delays.
- ITC Investigation: The U.S. International Trade Commission (ITC) is also separately investigating Adani and others for Section 337 violations (patent infringement) following a complaint by Trinasolar.
Conclusion: A Precarious U.S. Market Position
The USPTO’s refusal to invalidate First Solar’s patents leaves Mundra Solar with very few options other than proving non-infringement in open court. With its primary defense (challenging the patent’s validity) now closed, Adani must win on technical merits in Delaware or risk a “limited exclusion order” that could bar its solar products from entering the U.S. entirely.
