Maxeon Solar Pte Ltd v. Canadian Solar Inc

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: Maxeon Solar Pte. Ltd. (Singapore)
  • Defendant: Canadian Solar, Inc. (Canada)
  • Plaintiff’s Counsel: Vinson & Elkins LLP
• Case Identification: 2:24-cv-00210, E.D. Tex., 03/25/2024
• Venue Allegations: Plaintiff alleges venue is proper because Defendant is not a resident of the United States and may be sued in any judicial district. The complaint further alleges Defendant conducts substantial business in Texas, including operating a manufacturing facility in Mesquite and having a U.S. subsidiary, Recurrent Energy, headquartered in Austin.
• Core Dispute: Plaintiff alleges that Defendant’s Tunnel Oxide Passivated Contact (TOPCon) solar modules infringe three U.S. patents related to high-efficiency solar cell structures and manufacturing methods.
• Technical Context: The technology at issue is high-efficiency photovoltaic cell design, specifically TOPCon architecture, which represents a significant advancement over prior generation Passivated Emitter and Rear Cell (PERC) technology.
• Key Procedural History: The complaint notes that Plaintiff Maxeon is a 2020 spin-off of SunPower Corporation, the original assignee of the asserted patents. It also states that the '053 patent is a divisional of the application that issued as the '516 patent, indicating a direct family relationship between the two. No other significant procedural events are mentioned in the complaint.

Case Timeline

Date	Event
2008-02-20	Priority Date for '516 and '053 Patents
2012-07-17	U.S. Patent No. 8,222,516 Issues
2014-11-04	U.S. Patent No. 8,878,053 Issues
2014-12-22	Priority Date for '315 Patent
2019-01-01	Canadian Solar allegedly begins developing TOPCon technology
2022-02-15	U.S. Patent No. 11,251,315 Issues
2022-12-15	Canadian Solar announces mass production of TOPCon modules
2023-12-31	Canadian Solar's Texas manufacturing facility begins production (approx.)
2024-03-25	Complaint Filed

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

U.S. Patent No. 8,222,516 - "Front Contact Solar Cell with Formed Emitter"

Issued July 17, 2012

The Invention Explained

• Problem Addressed: The patent addresses the need for relatively efficient and cost-effective front-contact solar cells, which are distinct from backside-contact cells often preferred for aesthetic reasons in residential applications ('516 Patent, col. 1:29-43). The goal is to maximize power generation in a front-contact architecture.
• The Patented Solution: The invention is a "bipolar" solar cell structure featuring a backside junction. This junction is formed between an N-type silicon substrate and a P-type polysilicon emitter layer located on the cell's backside. Critically, the metal contacts that draw current are split: a negative contact on the front connects to the N-type substrate, while a positive contact on the back connects to the P-type emitter ('516 Patent, Abstract; Fig. 1). An oxide layer is situated between the substrate and the backside emitter ('516 Patent, col.2:62-65).
• Technical Importance: This design combines features of both front- and back-contact cells to optimize performance by managing the electrical junction and current collection paths to reduce energy loss ('516 Patent, col. 2:39-49).

Key Claims at a Glance

• The complaint asserts independent claim 9 and dependent claim 10 ('516 Patent, col. 6:42-65; Compl. ¶45).
• Independent Claim 9 requires:
  • A solar cell with a front side and a backside.
  • A substrate with a textured front surface.
  • An emitter layer formed over the back surface of the substrate, forming a backside junction.
  • An oxide layer between the back surface of the substrate and the emitter layer.
  • A first metal contact on the front side electrically connected to the substrate.
  • A second metal contact on the backside electrically connected to the emitter layer.
  • The contacts being configured to allow an external circuit to be powered.
• The complaint does not explicitly reserve the right to assert additional claims.

U.S. Patent No. 8,878,053 - "Front Contact Solar Cell with Formed Emitter"

Issued November 4, 2014

The Invention Explained

• Problem Addressed: As a divisional of the '516 patent's application, the '053 patent addresses the same technical challenge: creating a cost-effective and efficient front-contact solar cell ('053 Patent, col. 2:10-22).
• The Patented Solution: The '053 patent claims a method for fabricating the solar cell structure described in the '516 patent. The key steps include forming an oxide layer over the back of a silicon substrate, forming a polysilicon layer over the oxide, and then diffusing dopants into both the front surface of the substrate and the backside polysilicon layer to create the necessary junctions for operation. The method concludes with forming the front metal contact ('053 Patent, Abstract; col. 6:14-46).
• Technical Importance: Protecting the manufacturing process is critical in the solar industry; this patent seeks to cover the specific sequence of steps that produces the novel cell architecture ('053 Patent, col. 5:7-14).

Key Claims at a Glance

• The complaint asserts independent claims 9 and 16, and dependent claims 12 and 14-20 ('053 Patent, col. 6:51-col. 8:24; Compl. ¶65).
• Independent Claim 16 requires the method steps of:
  • Forming an oxide layer over a back surface of a silicon substrate.
  • Forming a layer of polysilicon over the oxide layer.
  • Diffusing dopants into the polysilicon layer to form a backside junction.
  • Diffusing dopants into the front surface of the silicon substrate.
  • Forming a metal contact on the front surface electrically coupled to the substrate.
• The complaint does not explicitly reserve the right to assert additional claims.

U.S. Patent No. 11,251,315 - "Solar Cells with Improved Lifetime, Passivation and/or Efficiency"

Issued February 15, 2022

Technology Synopsis

This patent discloses a method for fabricating solar cells with improved electrical properties. The invention involves forming a dielectric region and an emitter region on a silicon substrate, and then heating the cell to a temperature above 900°C. This high-temperature step is designed to "getter," or draw, performance-degrading metal impurities from the active silicon substrate into the emitter region, thereby improving the cell's carrier lifetime and overall efficiency ('315 Patent, Abstract; col. 5:26-44).

Asserted Claims

Independent claim 10 and dependent claims 11 and 13-15 are asserted (Compl. ¶80).

Accused Features

The complaint alleges that Canadian Solar's TOPCon solar modules have a structure that infringes claim 10, including a silicon substrate with a specific dopant concentration, a dielectric region on the backside, and an emitter region with metal impurities formed over it, consistent with the patented structure (Compl. ¶¶81-88).

III. The Accused Instrumentality

Product Identification

The accused products are Canadian Solar’s TOPCon solar modules, including but not limited to the TOPBiHiKu7, TOPBiHiKu6, and TOPHiKu6 series solar modules (Compl. ¶40).

Functionality and Market Context

The accused products are high-efficiency N-type Tunnel Oxide Passivated Contact (TOPCon) solar modules (Compl. ¶10). The complaint, citing a Canadian Solar webinar, describes the accused cell structure as comprising an N-type silicon (Si) substrate, a p+ emitter on the front, and a backside structure containing a silicon oxide (SiOx) tunnel layer and an n+ polysilicon (poly-Si) layer (Compl. ¶¶49-53). A diagram from this webinar illustrates the alleged structure of the accused TOPCon cells (Compl. p. 22, "TOPBiHiKu7 TOPCon Design"). The complaint alleges that TOPCon technology is emerging as the predominant replacement for older PERC technology and that Canadian Solar has aggressively entered this market, with TOPCon cells now accounting for half of its total cell capacity (Compl. ¶¶5, 11).

IV. Analysis of Infringement Allegations

'516 Patent Infringement Allegations

Claim Element (from Independent Claim 9)	Alleged Infringing Functionality	Complaint Citation	Patent Citation
a solar cell having a front side facing the sun to collect solar radiation during normal operation and a backside opposite the front side	The accused TOPBiHiKu7 modules include a solar cell with a "front side" and a "backside" as identified in a Canadian Solar webinar.	¶48	col. 6:42-45
a substrate having a textured front surface	The accused modules have an "N-type Si" substrate with a textured front surface, as shown in webinar diagrams.	¶50	col. 6:46
an emitter layer formed over a back surface of the substrate, the emitter layer forming a backside junction with the substrate	An "n+ poly-Si" layer is alleged to be the emitter layer, formed on the backside of the N-type Si substrate to create a backside junction.	¶¶51-52	col. 6:47-49
an oxide layer formed between the back surface of the substrate and the emitter layer	A "SiOx" layer is alleged to be formed between the N-type Si substrate and the "n+ poly-Si" emitter layer.	¶53	col. 6:50-51
a first metal contact making an electrical connection to the substrate on the front side of the solar cell	A "Screen printed AgAl contact" is alleged to be the first metal contact on the front side, connected to the N-type Si substrate.	¶54	col. 6:52-54
a second metal contact making an electrical connection to the emitter layer on the backside of the solar cell, the first metal contact and the second metal contact being configured to allow an external electrical circuit to be powered by the solar cell	A "Screen printed Ag contact" is alleged to be the second metal contact on the backside, connected to the "n+ poly-Si" layer. The product datasheet shows the cell powers a circuit.	¶¶55-56	col. 6:55-60

• Identified Points of Contention:
  • Scope Questions: A central question may be whether the term "emitter layer" as used in the patent reads on the accused product's "n+ poly-Si" layer. The '516 patent's detailed description consistently refers to a "P-type doped polysilicon emitter" ('516 Patent, col. 2:28-31) forming a junction with an N-type substrate. The complaint alleges the accused product has an "n+" layer on its N-type substrate. This raises the question of whether the claim term "emitter layer" is limited by the specification to a P-type layer, which could create a mismatch with the accused product's structure.
  • Technical Questions: The complaint relies on a webinar diagram to identify the layers of the accused cell (Compl. p. 22). A technical question for the court will be whether this marketing-level diagram accurately reflects the manufactured cell's physical structure and chemical composition sufficient to meet the claim limitations.

'053 Patent Infringement Allegations

Claim Element (from Independent Claim 16)	Alleged Infringing Functionality	Complaint Citation	Patent Citation
A method of fabricating a solar cell comprising: forming an oxide layer over a back surface of a silicon substrate	Based on the accused product's structure, the complaint alleges Canadian Solar performs the step of forming a SiOx layer on the back of its N-type Si substrate.	¶68	col. 8:1-2
forming a layer of polysilicon over the oxide layer	The complaint alleges the method includes forming an "n+ poly-Si" layer over the SiOx layer.	¶69	col. 8:3-4
diffusing dopants into the layer of polysilicon to form a backside junction with the silicon substrate	The complaint infers this step is performed because the designation of the backside layer as "n+" indicates dopants have been diffused into it to form a junction.	¶70	col. 8:5-7
diffusing dopants into a front surface of the silicon substrate...	The complaint infers this step is performed because the accused product has a "p+ emitter" region on the front, indicating dopants were diffused into the front surface.	¶71	col. 8:8-11
forming a metal contact on the front surface of the silicon substrate, wherein the metal contact is electrically coupled to the silicon substrate	The complaint alleges the method includes forming a "screen printed AgAl contact" on the front surface of the N-type Si substrate.	¶72	col. 8:12-15

• Identified Points of Contention:
  • Evidentiary Questions: The infringement allegations for this method patent are based on inferences drawn from the final product's alleged structure (Compl. ¶67). A key point of contention will be whether Plaintiff can produce evidence that Defendant’s manufacturing process actually performs the claimed "diffusing" steps, as opposed to an alternative process (e.g., in-situ doping during deposition) that results in a similar structure but does not meet the claim limitations.
  • Scope Questions: The interpretation of "diffusing dopants" will be critical. The patent describes a process involving a separate "drive-in step" ('053 Patent, col. 4:51-64). The court will need to determine if the term "diffusing" is limited to such a step or if it can be construed more broadly to cover other methods of introducing dopants.

V. Key Claim Terms for Construction

• The Term: "emitter layer" ('516 Patent, Claim 9)

• Context and Importance: The definition of this term is central to the infringement analysis for the '516 patent. The patent's specification describes a P-type emitter on an N-type substrate, while the complaint accuses a product with an n+ layer on an N-type substrate. Practitioners may focus on this term because its construction could determine whether a fundamental structural mismatch exists between the patent's teachings and the accused product.

• Intrinsic Evidence for Interpretation:

  • Evidence for a Broader Interpretation: The plain language of claim 9 recites "an emitter layer" without specifying a dopant type (P-type or N-type). This may support an interpretation based on its function, covering any layer that collects charge carriers.
  • Evidence for a Narrower Interpretation: The specification repeatedly and exclusively describes the invention with a "P-type doped polysilicon emitter" ('516 Patent, col. 2:28-31; Abstract). A defendant may argue that this consistent description defines the term within the context of the patent, thereby limiting the claim scope to P-type emitters.

• The Term: "diffusing dopants" ('053 Patent, Claim 16)

• Context and Importance: This method step limitation is critical because the complaint infers its performance from the final product structure. The defendant may argue its manufacturing process does not practice this specific step. The construction of "diffusing" will determine whether alternative doping techniques fall within the claim's scope.

• Intrinsic Evidence for Interpretation:

  • Evidence for a Broader Interpretation: A party could argue that "diffusing" should be given its plain and ordinary meaning, covering any process where dopants are caused to migrate into the silicon or polysilicon, regardless of the specific technique.
  • Evidence for a Narrower Interpretation: The patent specification describes a process of applying a dopant source and then performing a "dopant drive-in step" in a furnace ('053 Patent, col. 4:51-64). A party may argue that this specific embodiment defines "diffusing" as a distinct, subsequent thermal step, which could exclude integrated processes like in-situ doping where deposition and doping occur concurrently.

VI. Other Allegations

• Indirect Infringement: The complaint alleges induced infringement of the '516 and '315 patents. The factual basis for inducement includes Defendant’s alleged marketing, creation of distribution channels, and supplying instructions or manuals for the accused TOPCon modules to customers and distributors in the U.S., such as Sol Systems (Compl. ¶¶57, 89).
• Willful Infringement: Willfulness is alleged for all three asserted patents. The complaint bases this allegation on the assertion that Defendant has had knowledge of the patents "at least as early as the filing date of this Complaint" and has nevertheless continued its allegedly infringing conduct (Compl. ¶¶59, 74, 91).

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

• A core issue will be one of definitional scope: can the term "emitter layer", which is described exclusively as P-type in the '516 patent's specification, be construed to cover the "n+ poly-Si" layer in the accused TOPCon cell? The outcome of this claim construction dispute will likely determine infringement of the '516 patent.
• A key evidentiary question will be one of process verification: can the Plaintiff prove that Canadian Solar’s manufacturing method practices the specific "diffusing dopants" step of the '053 patent, or will discovery reveal a different, non-infringing doping technique? The complaint's reliance on inferring process steps from final product marketing materials places a high burden of proof on the Plaintiff.
• The case will also turn on a question of technical mapping: do the high-level diagrams and marketing materials cited in the complaint provide sufficient technical detail to prove, by a preponderance of the evidence, that the physical and chemical structure of the mass-produced accused solar cells meets every limitation of the asserted claims?