DCT

1:25-cv-00582

First Solar Inc v. Canadian Solar Inc

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 1:25-cv-00582, D. Del., 05/09/2025
  • Venue Allegations: Venue is asserted based on certain defendants being incorporated in Delaware, and on all defendants purposefully directing activities toward the U.S. and placing products into the stream of commerce with the expectation of sales in Delaware.
  • Core Dispute: Plaintiff alleges that solar cells manufactured overseas by Defendant using a patented process are unlawfully imported into, used, and sold in the U.S., infringing a patent related to high-efficiency TOPCon solar cell manufacturing.
  • Technical Context: The technology at issue is Tunnel Oxide Passivated Contact (TOPCon), an advanced method for manufacturing high-efficiency solar cells that reduces electrical losses at the cell's surfaces.
  • Key Procedural History: The complaint alleges that Defendant was on notice of potential infringement as of a July 2024 First Solar press release and received direct written notice of infringement of the patent-in-suit on September 10, 2024. The complaint also references evidence, including scanning transmission electron microscopy (STEM) images, from a U.S. International Trade Commission (ITC) investigation (No. 337-TA-1425) concerning Defendant’s importation of TOPCon solar cells.

Case Timeline

Date Event
2009-04-21 ’074 Patent Priority Date
2015-09-08 ’074 Patent Issue Date
2024-07-19 First Solar press release announcing TOPCon patent ownership
2024-09-10 First Solar sends notice letter to Canadian Solar
2025-05-09 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," Issued September 8, 2015

The Invention Explained

  • Problem Addressed: A key challenge in solar cell efficiency is the undesirable "recombination" of charge carriers (electrons and holes), particularly at the physical surfaces of the silicon substrate. This recombination reduces the amount of electrical current that can be collected, thereby lowering the cell's overall power output (Compl. ¶48; ’074 Patent, col. 16:49-53). Additionally, the industry requires manufacturing methods that are both cost-effective and capable of producing highly efficient cells (’074 Patent, col. 1:31-42).
  • The Patented Solution: The patent discloses a method for fabricating a solar cell structure designed to minimize recombination and improve charge collection. The process involves depositing a very thin amorphous "interface passivation layer" onto a silicon wafer, followed by a "doped conductive and passivating layer." Crucially, the entire assembly is then subjected to a high-temperature thermal treatment (above 500°C). This heat treatment simultaneously crystallizes the conductive layer and causes the dopant to diffuse through the thin interface layer. This creates what the patent calls "shortened charge carrier flow paths," allowing electricity to be collected more efficiently without requiring costly and complex steps like etching metal contacts directly to the substrate (’074 Patent, col. 19:14-35, col. 16:15-24; Compl. ¶¶51, 60). The structure is illustrated conceptually in the patent's Figure 8 (Compl. ¶52).
  • Technical Importance: This method provides a pathway to create TOPCon solar cells that achieve high efficiency by both passivating the substrate surface to reduce recombination and creating highly conductive pathways for charge extraction (’074 Patent, col. 1:43-52; Compl. ¶5).

Key Claims at a Glance

  • The complaint asserts independent claim 1 and dependent claims 2, 4, and 8 (Compl. ¶¶68-71, 82-84).
  • Independent Claim 1 requires a method of fabricating a solar cell with the following essential steps:
    • 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 layer;
    • providing thermal treatment at 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, wherein the diffused dopant provides shortened charge carrier flow paths between the substrate and electrodes.
  • The complaint expressly reserves the right to assert additional claims based on discovery (Compl. ¶91).

III. The Accused Instrumentality

Product Identification

  • The accused instrumentalities are Canadian Solar’s TOPCon solar modules, including but not limited to the TOPBiHiKu and TOPHiKu product lines (Compl. ¶¶8, 61-62).

Functionality and Market Context

  • The complaint alleges these products are based on "N-type Bifacial TOPCon Technology" and are marketed as offering high module power, high efficiency, and superior bifaciality (i.e., the ability to generate power from light hitting the rear side of the panel) (Compl. ¶¶30-31, 63). The core of the infringement allegation is that these products contain solar cells that are manufactured overseas using the process claimed in the ’074 Patent and are then imported, offered for sale, and sold within the U.S. (Compl. ¶¶8, 85). A diagram from a Canadian Solar webinar allegedly depicts the structure of the accused TOPCon solar cells (Compl. ¶64).

IV. Analysis of Infringement Allegations

’074 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
A method of fabricating a solar cell comprising: providing a wafer as a central substrate; The accused manufacturing process allegedly uses an N-type doped silicon crystal wafer, identified as the "N-type Si" layer in a product schematic (Compl. ¶73). A webinar diagram shows this "N-type Si" layer as the central substrate of the cell (Compl. ¶72). ¶73 col. 19:15-16
depositing or growing at least one amorphous interface passivation layer over the substrate; The process allegedly deposits a layer of amorphous silicon oxide ("SiOx") on the back surface of the substrate to reduce electron recombination (Compl. ¶74). ¶74 col. 19:17-18
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 process allegedly deposits a conductive and passivating layer of polysilicon heavily doped with an N-type dopant (phosphorus), identified as the "n+ poly-Si" layer, onto the SiOx layer (Compl. ¶75). ¶75 col. 19:19-22
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...through the at least one interface passivation layer; The process allegedly applies a thermal treatment that crystallizes the "n+ poly-Si" layer and causes the phosphorus dopant to diffuse through the SiOx layer and into the central substrate (Compl. ¶76). This allegation is supported by a graph from product testing showing elevated phosphorus levels diffusing from the surface into the substrate (Compl. ¶77). ¶¶76-78 col. 19:23-29
and providing metallization as electrodes which directly contact the at least one conductive and passivating layer...wherein the dopant diffused through the...interface passivation layer provides shortened charge carrier flow paths between the substrate and the electrodes... The process allegedly adds metal electrodes that directly contact the "n+ poly-Si" layer (Compl. ¶79). This allegation is supported by STEM images from an ITC investigation, which purport to show the silver electrode making direct physical contact with the polysilicon conductive layer (Compl. ¶80). The complaint alleges this structure results in shortened charge paths as described in the patent (Compl. ¶81). ¶¶79-81 col. 19:30-35
  • Identified Points of Contention:
    • Technical Questions: A central allegation—that the manufacturing process includes a thermal treatment of at least 500°C—is inferred from testing data showing phosphorus diffusion (Compl. ¶¶77-78). A key technical question for the court will be whether the observed level of diffusion necessarily requires the claimed high-temperature step, or if it could be achieved through other means. The case may rely on expert testimony to resolve this inference.
    • Scope Questions: Claim 1 requires that the diffused dopant "provides shortened charge carrier flow paths." The complaint alleges this is met by pointing to the observed diffusion and referencing the patent's conceptual figures (Compl. ¶81). This raises a question of functional scope: does the accused cell actually operate in the specific manner required by this functional limitation, and what evidence will be required to prove it?
    • Factual Questions: The claim requires that electrodes "directly contact" the conductive layer. The complaint presents STEM images showing contact at "multiple spots" (Compl. ¶80). This raises a factual question about the nature and extent of this contact and whether it meets the standard required by the claim, which may become a point of dispute.

V. Key Claim Terms for Construction

  • The Term: "shortened charge carrier flow paths"

    • Context and Importance: This term appears in the final "wherein" clause of claim 1 and describes a functional result of the claimed method. Proving that the accused process achieves this specific outcome is essential to proving infringement. Practitioners may focus on this term because its meaning is defined relative to a baseline, which is illustrated conceptually in the patent's Figures 4 and 5, contrasting a longer path with the "shortened" one (’074 Patent, figs. 4-5; Compl. ¶¶56-58).
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: The claim language itself is open-ended, simply requiring "shortened" paths without specifying a required degree of shortening.
      • Evidence for a Narrower Interpretation: The patent specification provides specific context by contrasting the "shortened, curved path" in Figure 5 with the less direct path in Figure 4, explaining that the effect is due to increased conductivity near the back surface from the diffused dopant (’074 Patent, col. 16:47-59). An argument could be made that the term requires this specific mechanism and resulting path shape.

  • The Term: "directly contact"

    • Context and Importance: This term defines the physical relationship between the electrodes and the conductive layer. Its construction is critical because the complaint relies on STEM images from an ITC proceeding to show this contact, arguing that an intermediate insulating layer would prevent current flow (Compl. ¶¶79-80).
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: The plain meaning of "direct" implies the absence of an intervening substance. The patent's general description does not appear to impose a stricter requirement.
      • Evidence for a Narrower Interpretation: The specification, in contrasting its invention with prior art, might provide context suggesting a particular quality or uniformity of contact is required. A party could argue that the complaint's own evidence, showing contact at "multiple spots" (Compl. ¶80), does not constitute the full and complete "direct contact" envisioned by the patent.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges that Defendant induces infringement by its subsidiaries, distributors, and customers. This is allegedly accomplished by advertising the products, establishing U.S. distribution channels, and providing technical specifications, manuals, and support that instruct on the use of the infringing products (Compl. ¶¶86-87).
  • Willful Infringement: Willfulness is alleged based on both pre- and post-suit knowledge. The complaint asserts Defendant had knowledge from a July 2024 First Solar press release about its TOPCon patent portfolio, and received actual notice via a letter identifying the ’074 Patent on September 10, 2024. The complaint alleges that despite this knowledge, Defendant refused to take a license and continued its infringing activities (Compl. ¶¶9, 88, 90).

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

  • A core issue will be one of evidentiary inference: Does the complaint's technical evidence of phosphorus diffusion in the final product conclusively prove that the accused solar cells were manufactured using the claimed method step of a thermal treatment at 500°C or higher, or can Defendant demonstrate that a similar diffusion profile can be achieved via a non-infringing process?
  • A second central question will be one of functional operation: Beyond structural similarity, does the accused solar cell, as a result of the diffused dopant, actually function to create the "shortened charge carrier flow paths" as described and claimed in the patent? Proving this functional aspect of the claim will be critical for the plaintiff.
  • Finally, the case may turn on a question of definitional and factual scope: What quality and extent of physical connection is required to meet the "directly contact" limitation of the claim, and do the complaint's STEM images—showing contact at discrete points—satisfy that standard?