BYD America Asks a California Court to Declare First Solar's TOPCon Solar Cell Patent Not Infringed, Invalid, and Unenforceable.

The complaint

The case is BYD America LLC v. First Solar, Inc., No. 3:26-cv-10776 (N.D. Cal.), filed September 21, 2026 in the San Francisco Division with a jury demand. BYD America is a Delaware limited liability company based in Pasadena, California. The complaint alleges, on information and belief, that First Solar is a Delaware corporation based in Tempe, Arizona that operates a research and development facility in Santa Clara, California.

The dispute behind it

According to the complaint, First Solar wrote to BYD on June 11, 2025 alleging that BYD's n-type TOPCon products infringe the '074 patent. First Solar filed an ITC complaint on February 24, 2026 asking for a general exclusion order covering TOPCon solar cells and products containing them, and the investigation is Certain TOPCon Solar Cells, Modules, Panels, Components Thereof, and Products Containing Same, Inv. No. 337-TA-1494. BYD says it intervened, that First Solar then served a claim chart accusing its NLBK-36 modules, and that First Solar has since moved to dismiss the investigation without prejudice while pursuing district court suits on the patent against other solar manufacturers, including Nos. 1:26-cv-00210, 1:25-cv-00582, and 1:25-cv-00223 in the District of Delaware.

What the patent covers

U.S. Patent 9,130,074, titled High-efficiency solar cell structures and methods of manufacture, issued September 8, 2015. Claim 1 covers a method of fabricating a solar cell: providing a wafer as a central substrate, depositing or growing at least one amorphous interface passivation layer over it, depositing a doped conductive and passivating layer on that layer, applying a thermal treatment at about 500 degrees C or higher that at least partly crystallizes the conductive and passivating layer and diffuses the dopant through the interface passivation layer, and then providing metallization electrodes that directly contact the conductive and passivating layer, with the diffused dopant providing shortened charge carrier flow paths between the substrate and the electrodes. Claims 2, 4, and 8 depend from claim 1 and add, respectively, an antireflective or low reflective index layer on the back of the cell, perforation of the interface passivation layer by the thermal treatment, and diffusion of dopant into the substrate to form a high-low or p-n junction.

BYD's three counts

Noninfringement: BYD alleges that its modules are not made by the claimed method because it does not perform the claim 1 steps, and that the applicant disclaimed, during prosecution, processes that fire or force metal through underlying layers of the cell, which BYD says resemble its own methods. Invalidity: BYD alleges the asserted claims are anticipated or obvious over a September 2008 European Photovoltaic Solar Energy Conference paper on polysilicon tunnel junctions, charted in Exhibit 2, and indefinite and lacking written description under 35 U.S.C. 112 because the claims do not say what the shortened flow paths are measured against. Unenforceability: BYD alleges, on information and belief, that the 2008 paper was withheld from the USPTO with intent to deceive and that Figure 1 of the patent was copied from it, and, also on information and belief, that researchers at two third-party organizations contributed to the claimed subject matter, so First Solar does not hold valid rights. The complaint adds that a Chinese patent authority found the same paper invalidates a Chinese counterpart patent.

BYD asks for the three declarations, a finding that the case is exceptional under 35 U.S.C. 285, and its costs and attorneys' fees.

What to watch next

The docket shows an entry titled transfer case filed October 19, 2026 (ECF No. 15), a reassignment of the case on October 20, a re-notice of a motion on October 22 (ECF No. 21), an administrative motion under Civil Local Rule 7-11 on October 30 (ECF No. 23), and an opposition to a motion on November 2 (ECF No. 24). Watch for the ruling on the transfer motion and for First Solar's response to the complaint, including any infringement counterclaim.