PTAB invalidates Trina Solar’s TOPCon patents, ending parallel U.S. proceedings against Canadian Solar

Context: In October 2024, Trina Solar brought a patent infringement action against subsidiaries of Canadian Solar, asserting two patents relating to TOPCon (Tunnel Oxide Passivated Contact) solar cell technology in the United States District Court for the District of Delaware. In parallel, proceedings were initiated before the U.S. International Trade Commission (ITC) under Section 337. The Delaware case was stayed at an early stage following an unopposed motion, initially pending the ITC investigation. The ITC proceedings were subsequently terminated. However, the district court action remained stayed pending inter partes review (IPR) of the asserted patents before the Patent Trial and Appeal Board (PTAB) of the United States Patent and Trademark Office (USPTO). The patents were challenged through multiple IPR proceedings, all of which resulted in the same outcome.

What’s new: In final written decisions, the PTAB has held that all claims of both asserted patents were unpatentable.

Direct impact: The PTAB decisions remove the legal basis of the Delaware infringement action. With all asserted claims invalidated (short of a successful appeal), the case cannot proceed to trial. Although the decisions are subject to appeal to the United States Court of Appeals for the Federal Circuit, they have an immediate practical effect. In practice, courts are unlikely to advance infringement proceedings once the underlying patents have been declared unpatentable, and the litigation is effectively halted. A successful appeal represents the only path for reviving the dispute. Even in that scenario, the case would resume from a stayed position and require further proceedings before any merits determination is reached.

Wider ramifications:

• The case highlights that even complex, multi-forum enforcement efforts may depend on the survival of a small number of patents, and can collapse if those patents fail in validity challenges. Canadian Solar achieved a similar win over Maxeon this year (January 16, 2026 ip fray article).
• But recent changes in the USPTO’s policies have drastically reduced the number of IPR petitions (December 2, 2025 ip fray article), so there will be fewer such situations going forward.