DCT

1:26-cv-00210

First Solar Inc v. Trina Solar Co Ltd

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Amended Complaint
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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 1:26-cv-00210, D. Del., 03/04/2026
  • Jurisdiction & Venue: Plaintiff alleges personal jurisdiction because Defendants conduct substantial business in the district, including marketing, selling, and distributing the accused products, and have placed the products into the stream of commerce with the knowledge and intent that they would be sold in Delaware; for certain foreign defendants, Plaintiff alternatively alleges personal jurisdiction under Federal Rule of Civil Procedure 4(k)(2). Plaintiff separately alleges venue is proper under 28 U.S.C. § 1400(b).
  • Core Dispute: Plaintiff alleges that Defendants manufacture, import, and sell TOPCon solar cells and modules using a patented method for fabricating high-efficiency solar cells.
  • Technical Context: The technology relates to Tunnel Oxide Passivated Contact (TOPCon) solar cells, an advanced photovoltaic technology designed to increase energy conversion efficiency by reducing electron recombination.
  • Key Procedural History: The complaint alleges that Plaintiff publicly announced its intent to enforce its TOPCon patent portfolio in July 2024 and provided Defendants with written notice of infringement of the patent-in-suit on September 10, 2024.

Case Timeline

Date Event
2009-04-21 U.S. Patent No. 9,130,074 Priority Date
2015-09-08 U.S. Patent No. 9,130,074 Issue Date
2024-07 First Solar publicly announces intent to enforce TOPCon patents
2024-09-10 First Solar provides written notice of infringement to Trina Solar
Late 2024 T1 Energy acquires Trina Solar's U.S.-based solar manufacturing assets
2026-03-04 Complaint Filing Date

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

U.S. Patent No. 9,130,074 - High-Efficiency Solar Cell Structures and Methods of Manufacture

  • Patent Identification: U.S. Patent No. 9,130,074, issued September 8, 2015 (the "’074 Patent").

The Invention Explained

  • Problem Addressed: In conventional solar cells, a significant portion of light-excited electrons are lost through "recombination" at the surfaces of the silicon substrate before they can be collected to generate electricity, which reduces the cell's overall efficiency Compl. ¶54
  • The Patented Solution: The invention describes a method of manufacturing a solar cell by depositing an "amorphous interface passivation layer" and a "conductive and passivating layer" containing a dopant onto a silicon wafer substrate Compl. ¶57 The structure is then subjected to a high-temperature thermal treatment (above 500° C) Compl. ¶57 This process is claimed to cause the dopant to diffuse through the layers, creating "shortened charge carrier flow paths" that allow electrons to travel more directly to the electrodes, thereby increasing efficiency and reducing recombination '074 Patent, claim 1 Compl. ¶¶61, 64 The patent explains this concept by contrasting a less efficient vertical-then-lateral electron path with a more direct, curved path to the electrodes '074 Patent, Figs. 4-5
  • Technical Importance: The method purports to improve solar cell efficiency and performance by simultaneously passivating the cell surface and creating more efficient pathways for electricity collection, while potentially simplifying the manufacturing process Compl. ¶57 Compl. ¶66

Key Claims at a Glance

  • The complaint asserts infringement of independent claim 1 and dependent claims 2, 4, and 8 Compl. ¶¶78-81 Compl. ¶¶91-93
  • The essential elements of independent claim 1 are:
    • 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 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 layer; and
    • providing metallization (electrodes) that directly contact the conductive layer after the thermal treatment;
    • wherein the diffused dopant provides shortened charge carrier flow paths between the substrate and the electrodes.
  • The complaint expressly reserves the right to assert additional claims Compl. ¶103

III. The Accused Instrumentality

Product Identification

The accused instrumentalities are Defendants' TOPCon solar cells and the solar modules that incorporate them, including the Vertex® N and Vertex® S+ product lines Compl. ¶8 Compl. ¶67

Functionality and Market Context

  • The complaint alleges that Defendants' products are manufactured using methods covered by the ’074 Patent Compl. ¶8 Marketing materials cited in the complaint describe the accused products as based on "n type i-TOPCon technology" and tout benefits such as high efficiency, high bifaciality, and low power degradation Compl. ¶68 Compl. ¶73
  • The complaint provides a diagram from a technical presentation by Trina Solar illustrating the structure of its TOPCon solar cell, which includes layers labeled "n-type Cz Si wafer," "Tunnel SiOx," and "n+ poly-Si" Compl. ¶82 This diagram forms a basis for the infringement allegations. The complaint also references a Trina Solar white paper that diagrams the "N-type solar cell structure," showing layers including a "Tunneling SiOx" and "N type poly-Si thin film" Compl. ¶70, p. 36

IV. Analysis of Infringement Allegations

’074 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
providing a wafer as a central substrate; Trina Solar is alleged to use an "n-type Cz Si wafer" as the central substrate in its TOPCon solar cells. ¶83 col. 7:4-6
depositing or growing at least one amorphous interface passivation layer over the substrate; Trina Solar allegedly deposits or grows a layer of amorphous silicon oxide, labeled "Tunnel SiOx," which acts as the interface passivation layer. ¶84 col. 7:7-13
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; Trina Solar allegedly deposits a conductive and passivating layer of polysilicon heavily doped with phosphorus ("n+ poly-Si") on the "Tunnel SiOx" layer. ¶85 col. 7:14-25
providing 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... Trina Solar allegedly applies a thermal treatment of at least 500° C, which facilitates the diffusion of the phosphorus dopant from the "n+ poly-Si" layer through the "Tunnel SiOx" layer. ¶¶86-88 col. 17:20-25
providing metallization as electrodes which directly contact the at least one conductive and passivating layer following the thermal treatment thereof, Trina Solar allegedly adds metal electrodes ("Rear Ag contacts") that directly contact the "n+ poly-Si" layer. ¶89 col. 15:40-44
wherein the dopant diffused through the at least one interface passivation layer provides shortened charge carrier flow paths between the substrate and the electrodes... The complaint alleges that the diffusion of the phosphorus dopant creates higher conductivity and causes charge flow paths to curve toward the electrodes, shortening them in a manner conceptually similar to Figure 5 of the patent. ¶90 col. 18:50-57
  • Identified Points of Contention:
    • Evidentiary Question: The complaint alleges that the manufacturing process includes a thermal treatment "of at least a temperature of about 500 °C" Compl. ¶86 The evidence presented is a graph showing phosphorus diffusion, with the assertion that the observed "degree of diffusion... necessarily requires a thermal treatment" at that temperature Compl. ¶88 A central question will be whether Plaintiff can produce direct evidence of the specific temperatures used in Defendants' overseas manufacturing processes.
    • Functional Limitation Question: The final "wherein" clause requires that the process "provides shortened charge carrier flow paths." This raises the question of whether this is a functional result that must be independently proven, or if it is an inherent consequence of performing the preceding method steps. The defense may argue that their process does not result in the specific "shortened" paths as contemplated by the patent.
    • Scope Question: The claim requires deposition of an "amorphous" interface passivation layer Compl. ¶78 The complaint alleges Trina's "Tunnel SiOx" layer is amorphous Compl. ¶84 The interpretation of "amorphous" and whether the layer maintains this property through the high-temperature processing steps may become a point of dispute.

V. Key Claim Terms for Construction

  • The Term: "shortened charge carrier flow paths"

  • Context and Importance: This functional language appears in the "wherein" clause of claim 1 and defines the outcome of the patented method. The case may turn on whether the accused process achieves this specific result. Practitioners may focus on this term because it is not a standard structural element but a functional outcome that Plaintiff must prove the accused process achieves.

  • Intrinsic Evidence for Interpretation:

    • Evidence for a Broader Interpretation: The patent contrasts the invention with a prior art structure where charge flow is first vertical through a substrate and then lateral through an emitter layer ('074 Patent, Fig. 4). This may support an interpretation where any path more direct than that two-stage, right-angled path could be considered "shortened."
    • Evidence for a Narrower Interpretation: The patent illustrates the invention with a diagram showing a "shortened, curved path" '074 Patent, Fig. 5 Compl. ¶63 This could support a narrower construction requiring proof of a specific curved trajectory, not merely a more direct one.

  • The Term: "amorphous interface passivation layer"

  • Context and Importance: This term defines the nature of a key initial layer. The claim requires this layer be "amorphous" before a high-temperature treatment that "crystalliz[es], at least in part," a subsequent layer. The definition of "amorphous" and how that property is measured or defined in the context of the overall process will be important.

  • Intrinsic Evidence for Interpretation:

    • Evidence for a Broader Interpretation: The specification suggests that the thermal treatment can turn "amorphous silicon layers into polycrystalline silicon layers" '074 Patent, col. 15:5-7, suggesting "amorphous" is simply the pre-crystallization state.
    • Evidence for a Narrower Interpretation: The patent lists specific examples for the interface passivation layer, such as silicon oxide and silicon nitride '074 Patent, col. 7:10-13 A party could argue the term should be limited to materials that are known to be deposited in an amorphous state and serve the buffering function described in the patent '074 Patent, col. 16:10-14

VI. Other Allegations

  • Indirect Infringement: The complaint alleges induced infringement under 35 U.S.C. § 271(b), stating that Defendants encourage infringement by their subsidiaries, distributors, and customers through actions such as "advertising its products and their infringing uses," distributing "instructions and/or manuals," and providing technical support Compl. ¶¶95-98
  • Willful Infringement: The complaint alleges willful infringement based on Defendants' purported knowledge of the ’074 Patent. This knowledge is alleged to have arisen from a July 2024 industry press release by First Solar and, more specifically, from a written notice of infringement sent to Trina Solar on September 10, 2024 Compl. ¶99 Compl. ¶101

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

This case presents several focused technical and legal questions for the court's determination:

  1. A central issue will be one of functional proof: How will the functional limitation "provides shortened charge carrier flow paths" be construed, and what level of evidence is required to prove it? The dispute may focus on whether the inferential evidence of dopant diffusion shown in the complaint's graph Compl. ¶87 Compl. ¶88 is sufficient to establish that this specific functional result is achieved in the accused manufacturing process.

  2. A key evidentiary question will be one of process verification: Can Plaintiff obtain evidence to prove that Defendants' overseas manufacturing process includes a "thermal treatment at a temperature of about 500° C. or higher," as required by claim 1? The complaint's primary allegation on this point is an inference based on testing results Compl. ¶88, making this a likely target for discovery and expert testimony.

  3. The analysis will also involve a question of definitional scope: Does the accused "Tunnel SiOx" layer Compl. ¶84 meet the claim limitation of an "amorphous interface passivation layer," particularly given the subsequent high-temperature step that crystallizes an adjacent layer? The construction of "amorphous" and its role within the multi-step process will be critical to the infringement analysis.

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