Background
Trina Solar, a major Chinese solar panel manufacturer, acquired two U.S. patents in February 2024 covering tunnel oxide passivated contact (TOPCon) solar cell technology — a high-efficiency cell architecture that has become the dominant design in the global solar industry. The patents (U.S. Patent Nos. 9,722,104 and 10,230,009) described solar cells with silicon semiconductor substrates, tunnel oxide layers, and passivation films.
After acquiring the patents, Trina aggressively asserted them. It filed a Section 337 complaint at the U.S. International Trade Commission and a parallel $147 million lawsuit in China (Jiangsu High People’s Court) against competitors including Canadian Solar and Runergy. In response, Runergy filed an inter partes review (IPR) petition challenging the ‘104 patent, and Canadian Solar filed its own petition against the ‘009 patent. Canadian Solar later joined the Runergy petition via motion for joinder, and the Board consolidated the proceedings.
The Board’s Holding
The PTAB found all claims in both patents unpatentable as obvious under 35 U.S.C. § 103. The Board relied on combinations of prior art that included a 2013 publication from the Fraunhofer Institute for Solar Energy Systems — a leading German research institution — that described the TOPCon manufacturing process more than a year before the earliest patent filing date. Additional prior art from the 1980s provided foundational teachings on the individual elements of the claimed solar cell structures.
The petitioners showed that each claim element was known in the prior art and that a person of ordinary skill would have been motivated to combine these teachings to arrive at the patented solar cell designs. Trina Solar was unable to overcome this showing with evidence of secondary considerations of non-obviousness.
Key Takeaways
- All claims gone. The Board invalidated all 11 claims of the ‘104 patent and all 17 claims of the ‘009 patent, leaving Trina with no surviving U.S. patent claims on this technology.
- Prior art from public research institutions proved decisive. The 2013 Fraunhofer publication — a publicly available research paper — was the key prior art reference, underscoring the risk of patenting incremental improvements in fields with active academic research.
- Strategic use of IPR joinder. Canadian Solar’s decision to join Runergy’s existing petition (rather than filing independently) is a common but effective IPR tactic that consolidates resources and streamlines the challenge.
- Parallel global litigation continues. While the U.S. patent front is effectively closed, Trina’s $147M Chinese lawsuit over related patents remains pending, and a separate ITC investigation filed by First Solar against multiple Chinese manufacturers (including Trina) adds another layer to the global solar patent wars.
Why It Matters
TOPCon technology has emerged as the leading next-generation solar cell architecture, and the patents at stake here sat at the center of an escalating trade war between Chinese solar manufacturers. Trina’s attempt to weaponize recently acquired patents against competitors backfired when the PTAB found the technology was already well-described in public research. For the solar industry, this ruling removes a significant cloud of uncertainty over TOPCon manufacturing in the U.S. market. For patent strategists, it illustrates the risk of asserting patents whose claims are closely anticipated by published academic research — IPR petitioners know exactly where to look.