BYD America LLC v. First Solar Inc

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: BYD America LLC (Delaware)
  • Defendant: First Solar, Inc. (Delaware)
  • Plaintiff’s Counsel: White & Case LLP
• Case Identification: 3:26-cv-10766, N.D. Cal., 09/21/2026
• Venue Allegations: Plaintiff BYD alleges venue is proper in the Northern District of California because Defendant First Solar operates a research and development facility in the district, acquired the patent-in-suit via an acquisition of a company previously located in the district, employs at least one named inventor residing in the district, and has purposefully directed activities into the forum, including licensing communications and testing of allegedly infringing products.
• Core Dispute: Plaintiff seeks a declaratory judgment that its N-type TOPCon solar modules do not infringe Defendant's patent related to high-efficiency solar cell manufacturing, and further alleges the patent is invalid and unenforceable.
• Technical Context: The dispute centers on Tunnel Oxide Passivated Contact (TOPCon) technology, a method for manufacturing high-efficiency crystalline silicon solar cells, which is a key area of competition in the global solar panel market.
• Key Procedural History: This declaratory judgment action was filed in the context of a broader dispute, which includes a parallel investigation at the International Trade Commission (ITC) initiated by First Solar against BYD and other solar product importers. The complaint notes that First Solar has moved to dismiss its own ITC action. The complaint also references prior statements made during the patent's prosecution, which it alleges create prosecution history estoppel, and makes significant allegations of inequitable conduct based on the applicant's alleged failure to disclose material prior art to the patent office.

Case Timeline

Date	Event
2008-09-01	Borden Reference publication date (approximate)
2009-04-21	'074 Patent Priority Date
2015-09-08	'074 Patent Issue Date
2025-06-11	First Solar sends letter to BYD alleging infringement
2026-02-24	First Solar files complaint in the ITC
2026-09-21	BYD files Complaint for Declaratory Judgment

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 9,130,074 - “High-efficiency solar cell structures and methods of manufacture”

• Issued: September 8, 2015

The Invention Explained

• Problem Addressed: The patent’s background section identifies a need for solar cells that achieve high operational efficiency (20% or more) but can be manufactured in a cost-effective manner, noting that existing high-efficiency cells often suffer from "cell structure complexity and/or manufacturing complexity" ’074 Patent, col. 1:36-39
• The Patented Solution: The invention describes a method for fabricating a solar cell by depositing a series of layers on a silicon wafer. A key aspect is the use of a high-temperature thermal treatment (about 500°C or higher) on a layered stack, which includes an "amorphous interface passivation layer" and an overlying "conductive and passivating layer" containing a dopant ’074 Patent, claim 1 According to the patent, this single thermal step serves multiple functions: it crystallizes the conductive layer and simultaneously causes the dopant to diffuse through the underlying passivation layer, creating "shortened charge carrier flow paths" that improve efficiency ’074 Patent, claim 1 ’074 Patent, col. 16:15-21 This process aims to create a highly passivated surface contact structure without complex manufacturing steps.
• Technical Importance: The described method relates to the formation of passivated contacts, a critical technology for reducing electrical losses at the metal-silicon interface and pushing the efficiency limits of crystalline silicon solar cells.

Key Claims at a Glance

• The complaint seeks a declaratory judgment of non-infringement of claims 1, 2, 4, and 8 (’074 Patent, ¶1). Independent claim 1 is central to the dispute.
• The essential elements of independent claim 1 include:
  • Providing a wafer as a central substrate.
  • Depositing or growing at least one amorphous interface passivation layer over the substrate.
  • Depositing at least one conductive and passivating layer (comprising a dopant) on the interface passivation layer.
  • Providing a thermal treatment at a temperature of about 500°C or higher, which crystallizes the conductive layer and facilitates diffusion of the dopant through the interface passivation layer.
  • Providing metallization as electrodes that directly contact the conductive and passivating layer after the thermal treatment.
  • Wherein the diffused dopant provides "shortened charge carrier flow paths" between the substrate and electrodes.
• The complaint notes that claims 2, 4, and 8 are dependent on claim 1 (’074 Patent, ¶24).

III. The Accused Instrumentality

Product Identification

The accused instrumentalities are BYD's "N-type TOPCon solar modules," including those with the model designation NLBK-36 Compl. ¶2

Functionality and Market Context

The complaint identifies the accused products as being based on TOPCon (Tunnel Oxide Passivated Contact) solar cell technology Compl. ¶2 This technology is a leading approach for manufacturing high-efficiency solar cells. The complaint does not detail BYD's specific manufacturing process but instead bases its non-infringement case on categorical denials that its process includes the steps required by the asserted claims Compl. ¶22 The dispute arises from First Solar’s prior allegations in correspondence and an ITC proceeding that the manufacturing and sale of these products infringe the ’074 patent Compl. ¶2

IV. Analysis of Infringement Allegations

The complaint is for a declaratory judgment of non-infringement. The following table summarizes the non-infringement position asserted by BYD against the representative independent claim, based on the specific denials made in the complaint.

'074 Patent Infringement Allegations

Claim Element (from Independent Claim 1)	Alleged Infringing Functionality	Complaint Citation	Patent Citation
depositing or growing at least one amorphous interface passivation layer over the substrate;	The complaint alleges that the manufacturing process for the Accused Products does not perform this step as claimed Compl. ¶22a	¶22a	col. 19:13-15
depositing at least one conductive and passivating layer on the at least one interface passivation layer, the at least one conductive and passivating layer comprising a dopant;	The complaint alleges that the manufacturing process for the Accused Products does not perform this step as claimed Compl. ¶22b	¶22b	col. 19:16-20
providing a thermal treatment at a temperature of about 500° C. or higher, the thermal treatment crystallizing, at least in part, the at least one conductive and passivating layer and facilitating diffusion of the dopant...;	The complaint alleges that the manufacturing process for the Accused Products does not perform this step as claimed Compl. ¶22c	¶22c	col. 19:21-27
providing metallization as electrodes which directly contact the at least one conductive and passivating layer following the thermal treatment thereof, wherein the dopant diffused...provides shortened charge carrier flow paths...	The complaint alleges that the manufacturing process for the Accused Products does not perform this step as claimed Compl. ¶22d The complaint specifically raises prosecution history estoppel, arguing the applicant disclaimed processes involving firing or melting metal to penetrate underlying layers, and alleges BYD's methods are similar to those disclaimed methods Compl. ¶23	¶22d; ¶23	col. 19:28-col. 20:2

• Identified Points of Contention:
  • Prosecution History Estoppel: The complaint argues that during prosecution, the applicant distinguished the invention from prior art by stating the claimed method "eliminates the need to fire, melt, or otherwise force a metal to penetrate through underlying layers of a solar cell" Compl. ¶23 A central question will be whether BYD’s actual manufacturing process, which the complaint suggests is similar to the disclaimed methods Compl. ¶23, falls within the scope surrendered during prosecution.
  • Factual Dispute over Process Steps: The core of the non-infringement case rests on a factual dispute over whether BYD's TOPCon manufacturing process performs the specific sequence of depositing, thermal treatment, and metallization recited in claim 1 Compl. ¶22 The outcome will depend on a direct comparison of BYD's proprietary process with the claim limitations.
  • Indefiniteness: The complaint challenges the functional limitation "provides shortened charge carrier flow paths" as indefinite under 35 U.S.C. § 112, arguing the patent fails to provide a baseline for comparison, making it impossible to determine if a path has been "shortened" Compl. ¶31

V. Key Claim Terms for Construction

• The Term: "providing metallization as electrodes which directly contact the at least one conductive and passivating layer"

  • Context and Importance: This term is critical due to the prosecution history estoppel arguments. The patentability of the claim appears to have hinged on distinguishing the invention from prior art methods that required "firing" contacts through layers. The meaning of "directly contact" will determine whether the claim reads on processes that involve some interaction between the metal and underlying layers.
  • Evidence for a Broader Interpretation: A patentee might argue "directly contact" simply means the electrode is placed on the conductive layer without any intervening insulating film, and that some degree of inter-diffusion or alloying at the interface during formation does not negate "direct contact."
  • Evidence for a Narrower Interpretation: BYD's complaint provides strong evidence for a narrower view, citing the applicant's statement that the invention allows metallization "without the need for a conductive material to penetrate through any underlying layers of the solar cell" Compl. ¶23 This suggests "directly contact" should be construed to mean a purely surficial contact that excludes processes like firing or melting.

• The Term: "shortened charge carrier flow paths"

  • Context and Importance: This functional language appears in the "wherein" clause of claim 1 and describes the result of the preceding method steps. BYD alleges the term is indefinite Compl. ¶31 Its construction is crucial for determining if the claim is valid and, if so, whether the functional result is met.
  • Evidence for a Broader Interpretation: The patentee may argue that a person of ordinary skill in the art would understand the "shortening" to be relative to a structure lacking the claimed dopant diffusion, and that the language simply describes the inherent physical result of performing the claimed process.
  • Evidence for a Narrower Interpretation: The complaint argues that the patent "does not specify the starting or ending point for any such length calculations" and provides "no written description of path shortening via dopant diffusion," rendering the claim indefinite Compl. ¶31 Practitioners may focus on this term because functional "wherein" clauses are often scrutinized for indefiniteness and written description support under § 112.

VI. Other Allegations

• Indirect Infringement: The complaint seeks a declaratory judgment that it does not indirectly infringe the ’074 patent Compl. ¶27 However, it does not provide specific factual allegations from First Solar regarding inducement or contributory infringement that BYD is actively rebutting.
• Willful Infringement: As a declaratory judgment action filed by the accused infringer, there is no allegation of willfulness against BYD. However, the complaint establishes that First Solar was on notice of BYD’s products and had alleged infringement via a letter dated June 11, 2025 Compl. ¶15, which could serve as the basis for a future willfulness claim by First Solar should infringement be found.
• Invalidity: BYD alleges the asserted claims are invalid under 35 U.S.C. §§ 102, 103, and 112 Compl. ¶29 The primary basis is the "Borden Reference," a 2008 technical paper that allegedly anticipates or renders obvious the claimed invention Compl. ¶30 The complaint also asserts invalidity for indefiniteness and lack of written description under § 112, targeting the "shortened charge carrier flow paths" limitation Compl. ¶31
• Inequitable Conduct: The complaint makes a significant allegation of inequitable conduct, asserting that the inventors and their prosecution counsel intentionally withheld the material "Borden Reference" from the USPTO with an intent to deceive Compl. ¶¶36-39 As evidence, the complaint alleges that Figure 1 of the ’074 patent was copied directly from Figure 1 of the Borden Reference Compl. ¶¶43-45 The complaint presents a side-by-side comparison of Figure 1 from the '074 patent and Figure 1 from the Borden Reference, alleging they are identical Compl. ¶44 Compl. p. 11 It further alleges that the applicant falsely represented to the examiner that the combination of a conductive and passivating layer was "believed novel" when the inventor knew it had been "around like in the late 70s, so early 80s" Compl. ¶¶48-49
• Ownership: BYD challenges First Solar's standing to enforce the patent, alleging that First Solar is not the correct owner Compl. ¶53 The theory is that the authors of the Borden Reference, from which Figure 1 was allegedly copied, contributed to the conception of the claimed subject matter and are therefore un-named co-inventors. This would potentially give their employers (e.g., Applied Materials or the Fraunhofer Institute) ownership rights in the ’074 patent Compl. ¶54

VII. Analyst’s Conclusion: Key Questions for the Case

• Inequitable Conduct and the Borden Reference: A threshold issue will be the allegation of inequitable conduct. The court's evaluation of the striking similarity between the figures in the '074 patent and the undisclosed Borden Reference, and the related allegations of misrepresentation, will be critical. A finding of inequitable conduct would render the entire patent unenforceable, potentially resolving the case.
• Claim Scope and Prosecution Estoppel: A central question for the infringement analysis will be one of definitional scope: can the term "directly contact", in light of statements made during prosecution disclaiming the need for metal to "penetrate" underlying layers, be interpreted to read on BYD's accused manufacturing process? The application of prosecution history estoppel may significantly narrow the scope of the claims.
• Inventorship and Standing: The case raises a fundamental question of ownership: does the allegation of a copied figure from a prior art publication create a plausible claim of incorrect inventorship? If so, this could divest First Solar of the exclusive rights required to maintain an infringement action, presenting a significant challenge to its standing to enforce the patent.