DCT

1:24-cv-01115

Trina Solar Co Ltd v. Canadian Solar USA Inc

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 1:24-cv-01115, D. Del., 10/08/2024
  • Venue Allegations: Venue is alleged to be proper in the District of Delaware because each Defendant is a Delaware entity and therefore resides in the District.
  • Core Dispute: Plaintiff alleges that Defendant’s Tunnel Oxide Passivated Contact (TOPCon) solar cells and modules infringe patents related to the structure of high-efficiency solar cells.
  • Technical Context: The lawsuit concerns technology in the competitive high-efficiency photovoltaic market, where TOPCon architecture is a key approach to increasing solar cell power conversion efficiency by reducing energy losses at the electrical contacts.
  • Key Procedural History: The two asserted patents are from the same family; U.S. Patent No. 10,230,009 is a continuation of an application which is itself a continuation of the application that issued as U.S. Patent No. 9,722,104. The complaint does not mention any prior litigation or administrative proceedings involving these patents.

Case Timeline

Date Event
2014-11-28 Earliest Priority Date for '104 and '009 Patents
2017-08-01 U.S. Patent No. 9,722,104 Issues
2019-03-12 U.S. Patent No. 10,230,009 Issues
2023-01-01 Approximate Launch of Accused Products (First Quarter 2023)
2024-10-08 Complaint Filed

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

U.S. Patent No. 9,722,104 - “Solar cell and method for manufacturing the same”

  • Patent Identification: U.S. Patent No. 9,722,104, “Solar cell and method for manufacturing the same,” issued August 1, 2017 (the “'104 Patent”).

The Invention Explained

  • Problem Addressed: The patent background describes the general need for alternative energy resources and the basic operating principle of a solar cell, which relies on a p-n junction to separate light-generated electron-hole pairs to produce electric power (’104 Patent, col. 1:18-42). The implicit problem is the need to improve the efficiency and structure of such cells.
  • The Patented Solution: The invention proposes a specific solar cell structure designed to enhance performance. It features a semiconductor substrate with a very thin "tunnel layer" on one surface, followed by a "first conductive type semiconductor region" (’104 Patent, col. 7:51-64). This architecture, known in the industry as TOPCon, is designed to reduce energy losses from carrier recombination at the metal contacts. The patent also describes an "isolation portion" at the edge of the cell to prevent short-circuiting between the top and bottom conductive layers (’104 Patent, col. 13:1-7).
  • Technical Importance: This patent describes a TOPCon solar cell architecture, a significant technological approach for pushing photovoltaic efficiency beyond the limits of previous-generation cell designs by improving surface passivation (’104 Patent, Abstract).

Key Claims at a Glance

  • The complaint asserts at least independent claim 1 (Compl. ¶20).
  • The essential elements of independent claim 1 include:
    • A semiconductor substrate.
    • A tunnel layer on a first surface of the substrate.
    • A first conductive type semiconductor region on the tunnel layer.
    • A second conductive type semiconductor region on the opposite surface of the substrate.
    • First and second passivation films on their respective semiconductor regions.
    • First and second electrodes connected through openings in the respective passivation films.
    • An isolation portion at the edge of the substrate that excludes the tunnel layer and first semiconductor region.
    • The first passivation film covers the first surface of the substrate and the isolation portion together.

U.S. Patent No. 10,230,009 - “Solar cell and method for manufacturing the same”

  • Patent Identification: U.S. Patent No. 10,230,009, “Solar cell and method for manufacturing the same,” issued March 12, 2019 (the “'009 Patent”).

The Invention Explained

  • Problem Addressed: As a continuation in the same patent family, the '009 Patent addresses the same general problem of improving solar cell efficiency and structure ('009 Patent, col. 1:21-42).
  • The Patented Solution: The '009 Patent describes a solar cell structure highly similar to that of the '104 Patent but uses more specific terminology. It explicitly recites a "silicon semiconductor substrate," an "oxide layer" (instead of the more functional "tunnel layer"), and a "polysilicon layer" (instead of the more generic "first conductive type semiconductor region") ('009 Patent, Abstract). This suggests a more structurally defined version of the same underlying TOPCon technology, including the use of an emitter region and a specific edge isolation portion to prevent electrical contact between the cell's different layers ('009 Patent, col. 2:22-34).
  • Technical Importance: This patent provides a more concrete structural definition for a high-efficiency TOPCon solar cell, refining the inventive concept of the parent '104 Patent.

Key Claims at a Glance

  • The complaint asserts at least independent claim 1 (Compl. ¶46).
  • The essential elements of independent claim 1 include:
    • A silicon semiconductor substrate.
    • An oxide layer on a first surface of the substrate.
    • A polysilicon layer on the oxide layer.
    • An emitter region on the opposite surface of the substrate.
    • First and second passivation films on the polysilicon layer and emitter region, respectively.
    • First and second electrodes connected through openings in the respective passivation films.
    • An isolation portion preventing contact between the polysilicon layer and the emitter region.
    • The isolation portion excludes the oxide and polysilicon layers and is at an edge of the substrate.
    • The first passivation film covers the first surface of the substrate and the isolation portion together.

III. The Accused Instrumentality

Product Identification

The accused products are Defendant’s solar cells and modules that incorporate "Tunnel Oxide Passivated Contact ('TOPCon') solar cells" (Compl. ¶1). Specific product lines named are the TOPBiHiKu7 bifacial, TOPBiHiKu6 bifacial, and TOPHiKu6 monofacial solar modules, with a specific example being model CS6.1-54TM-455 (Compl. ¶¶13, 25).

Functionality and Market Context

The accused products are marketed as high-efficiency "N-type TOPCon Technology" solar modules (Compl. p. 8). A product datasheet included in the complaint shows the cell type as "TOPCon cells" (Compl. p. 8). The complaint alleges these products are manufactured, used, offered for sale, sold, and/or imported into the United States, with some modules being produced at a facility in Mesquite, Texas (Compl. ¶¶1, 14).

IV. Analysis of Infringement Allegations

The complaint relies heavily on a graphic from a February 2024 Canadian Solar webinar, which it calls the "Webinar Slide," to map the accused product's structure to the patent claims (Compl. ¶28, p. 9). This slide depicts a cross-section of a "TOPCon" cell with labeled layers.

'104 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
[a] a semiconductor substrate The accused cells contain an “N-Type Si” semiconductor substrate, identified as the large gray region in the Webinar Slide. ¶29 col. 6:46-50
[b] a tunnel layer on a first surface of the semiconductor substrate The accused cells contain a tunnel layer marked as “SiOx” (a silicon oxide) in teal on the Webinar Slide. ¶30 col. 7:51-55
[c] a first conductive type semiconductor region on the tunnel layer and containing impurities of a first conductive type The accused cells contain a first conductive type semiconductor region, shown in pink on the Webinar Slide and marked as “n⁺ poly-Si.” ¶31 col. 8:37-40
[d] a second conductive type semiconductor region on a second surface opposite to the first surface... The accused cells contain a second conductive type semiconductor region, marked in green on the Webinar Slide and designated as a “p⁺ emitter.” ¶32 col. 9:36-42
[e] a first passivation film on the first conductive type semiconductor region The accused cells contain a first passivation film comprised of an SiNₓ layer, based on reverse engineering. The Webinar Slide shows “SIN, H” at the bottom. ¶33 col. 10:1-5
[f] a first electrode formed on the first passivation film and connected to the first conductive type semiconductor region... The accused cells contain a first electrode marked as “Screen printed AG contact” at the bottom of the Webinar Slide. ¶34 col. 11:1-8
[g] a second passivation film on the second conductive type semiconductor region The accused cells contain a second passivation film comprised of AlOₓ, designated as the yellow region at the top of the Webinar Slide. ¶35 col. 10:1-5
[h] a second electrode formed on the second passivation film and connected to the second conductive type semiconductor region... The accused cells contain a second electrode designated at the top of the Webinar Slide as “Printed screen AgAl contact.” ¶36 col. 11:14-20
[i] an isolation portion for preventing a contact... [j] wherein the isolation portion excludes the tunnel layer... [k] wherein the first passivation film covers... the isolation portion... The accused cells contain an isolation portion that meets these limitations, an allegation based on reverse engineering conducted on an accused module. The Webinar Slide does not depict this feature. ¶¶37-39 col. 13:1-7

'009 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
[a] a silicon semiconductor substrate having a first conductive type The accused cells contain a “N-Type Si” semiconductor substrate, as shown in the large gray region of the Webinar Slide. ¶55 col. 6:49-54
[b] an oxide layer on a first surface of the silicon semiconductor substrate The accused cells contain an oxide layer marked as “SiOx” in teal in the Webinar Slide. ¶56 col. 7:13-19
[c] a polysilicon layer on the oxide layer and having the first conductive type The accused cells contain a polysilicon region shown in pink on the Webinar Slide and marked as “n⁺ poly-Si.” ¶57 col. 8:43-51
[d] an emitter region at a second surface of the silicon semiconductor substrate... The accused cells contain an emitter region marked in green on the Webinar Slide and designated as “p⁺ emitter.” ¶58 col. 10:3-9
[e] a first passivation film on the polysilicon layer The accused cells contain a first passivation film comprised of an SiNₓ layer, based on reverse engineering. ¶59 col. 10:62-67
[f] a first electrode connected to the polysilicon layer through an opening... The accused cells contain a first electrode marked as “Screen printed AG contact” at the bottom of the Webinar Slide. ¶60 col. 12:4-11
[g] a second passivation film on the emitter region The accused cells contain a second passivation film shown as the yellow region at the top of the Webinar Slide and comprised of AlOₓ. ¶61 col. 10:62-67
[h] a second electrode connected to the emitter region through an opening... The accused cells contain a second electrode designated at the top of the Webinar Slide as “Printed screen AgAl contact.” ¶62 col. 12:17-23
[i] an isolation portion for preventing a contact... [j] wherein the isolation portion excludes the oxide layer and the polysilicon layer... [k] the first passivation film covers... the isolation portion... The accused cells contain an isolation portion that meets these limitations, an allegation based on reverse engineering conducted on an accused module. The Webinar Slide does not depict this feature. ¶¶63-65 col. 2:22-34
  • Identified Points of Contention:
    • Evidentiary Questions: For both patents, the allegations concerning the "isolation portion" (elements [i], [j], and [k]) and the composition of the passivation films rely on "reverse engineering" rather than publicly available documents (Compl. ¶¶33, 37-39, 59, 63-65). The Webinar Slide does not depict an isolation portion. This raises the question of what technical evidence Plaintiff will produce to prove the existence and specific structure of these claimed features in the accused products.
    • Scope Questions: A potential dispute may arise from the use of the same evidence (the "Webinar Slide") to satisfy different claim terms in the two patents. For example, the complaint maps the accused "SiOx" layer to both the broader, functional term "tunnel layer" in the '104 Patent and the narrower, structural term "oxide layer" in the '009 Patent. The relationship between these terms and whether the accused feature meets the scope of each will be a question for claim construction.

V. Key Claim Terms for Construction

  • The Term: "isolation portion" (asserted in claim 1 of both the '104 and '009 Patents)

  • Context and Importance: This term is critical because its existence in the accused product is alleged based on non-public "reverse engineering" (Compl. ¶¶37, 63). The term is defined by multiple limitations regarding its function (preventing contact), structure (excluding certain layers), and location (at an edge portion). The defendant may argue its products lack a structure meeting all of these limitations, making the precise construction of this term central to the infringement analysis.

  • Intrinsic Evidence for Interpretation:

    • Evidence for a Broader Interpretation: The '104 Patent specification describes the feature functionally as "an isolation portion for preventing a contact between the first conductive type semiconductor region and the second conductive type semiconductor region" ('104 Patent, col. 2:20-23). This language could support an interpretation covering any structure that achieves this electrical isolation.
    • Evidence for a Narrower Interpretation: The figures and detailed description illustrate a specific embodiment where the isolation portion is an area from which the tunnel layer and the first conductive type region have been physically removed ('104 Patent, Fig. 2; col. 14:45-54). This could support a narrower construction requiring the physical absence of these layers at the cell's edge, not merely their electrical separation.

  • The Term: "tunnel layer" ('104 Patent, claim 1)

  • Context and Importance: Practitioners may focus on this term because the '104 Patent uses this functional term, while its continuation, the '009 Patent, uses the more specific structural term "oxide layer." Plaintiff alleges the same "SiOx" feature in the accused product meets both terms (Compl. ¶¶30, 56). The construction will determine if "tunnel layer" is broader than "oxide layer" and what proof is needed to show the accused "SiOx" layer performs the required tunneling function.

  • Intrinsic Evidence for Interpretation:

    • Evidence for a Broader Interpretation: The '104 Patent specification states a "tunnel layer may also function as a diffusion barrier" and "may include various materials through which majority carriers can be tunneled. For example, the tunnel layer ... may include oxides, nitrides, a semiconductor, and a conductive polymer" ('104 Patent, col. 8:5-13). This supports a broad, functional definition not limited to just oxides.
    • Evidence for a Narrower Interpretation: While allowing for various materials, the specification repeatedly uses a silicon oxide layer as the primary example, stating "the tunnel layer...may be formed of a silicon oxide (SiOx) layer" because it has "an excellent passivation characteristic and carriers can easily tunnel through the silicon oxide layer" ('104 Patent, col. 8:14-19). A defendant might argue that in the context of the invention, the term is functionally limited to materials with properties akin to the disclosed silicon oxide.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges both induced and contributory infringement for each patent. The inducement allegations are based on Defendant’s "affirmative acts of selling, distributing, and/or otherwise making available the Accused Products" and providing instructions, manuals, and technical support that allegedly encourage infringing use by customers and partners (Compl. ¶¶21, 47). The contributory infringement allegations state that the accused products are a material part of the invention, not a staple article of commerce, and are especially made or adapted for an infringing use (Compl. ¶¶22, 48).
  • Willful Infringement: Willfulness is alleged based on knowledge of the patents "since at least service of this complaint" (Compl. ¶¶41, 67). Plaintiff requests a finding of willfulness from at least the date of service and seeks enhanced damages (Compl. p. 22, ¶H). No pre-suit knowledge is alleged.

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

  • A central evidentiary question will be one of structural verification: Can Plaintiff's "reverse engineering" evidence prove that the accused solar cells contain an "isolation portion" that meets the specific structural and positional limitations recited in the claims, a feature not apparent from the defendant's public marketing materials?
  • A key issue for claim construction will be one of definitional scope: How will the court construe the relationship between the functional term "tunnel layer" in the '104 Patent and the more specific structural term "oxide layer" in the '009 Patent, and can the same accused "SiOx" feature satisfy both potentially different standards?