DCT
1:25-cv-00462
Mundra Solar PV Ltd v. First Solar Inc
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Mundra Solar PV Limited (India)
- Defendant: First Solar, Inc. (Delaware)
- Plaintiff’s Counsel: Shaw Keller LLP; Paul Hastings LLP
- Case Identification: 1:25-cv-00462, D. Del., 04/15/2025
- Venue Allegations: Venue is alleged to be proper in the District of Delaware because the Defendant is a corporation organized and existing under the laws of Delaware.
- Core Dispute: Plaintiff seeks a declaratory judgment that its Tunnel-Oxide Passivated Contact (TOPCon) solar cells do not infringe Defendant’s patents, which Plaintiff characterizes as being directed to Heterojunction (HJT) solar cell manufacturing methods.
- Technical Context: The lawsuit concerns advanced manufacturing methods for high-efficiency crystalline silicon solar cells, a key technology in the renewable energy sector.
- Key Procedural History: The action was precipitated by an April 1, 2025 demand letter from Defendant’s counsel alleging infringement. The complaint also notes that Defendant previously filed a lawsuit against another solar manufacturer, Jinko Solar, on one of the same patents, indicating a broader enforcement campaign related to its TOPCon patent portfolio.
Case Timeline
| Date | Event |
|---|---|
| 2009-04-21 | Priority Date for ’074 and ’732 Patents |
| 2015-09-08 | ’074 Patent Issue Date |
| 2017-05-30 | ’732 Patent Issue Date |
| 2024-07-19 | Defendant First Solar issues press release on TOPCon patent enforcement |
| 2025-02-25 | Defendant First Solar files complaint against Jinko Solar |
| 2025-04-01 | Defendant sends Demand Letter to Plaintiff Mundra Solar |
| 2025-04-15 | Complaint for Declaratory Judgment Filed |
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, “High-efficiency solar cell structures and methods of manufacture,” issued September 8, 2015. (Compl. ¶11).
The Invention Explained
- Problem Addressed: The patent addresses the challenge of creating solar cells with efficiencies of 20% or more in a cost-effective, high-volume manufacturing process, which was hindered by the complexity of existing methods. (’074 Patent, col. 1:33-42).
- The Patented Solution: The invention describes methods for fabricating solar cells by depositing amorphous silicon-containing layers over a substrate and then applying a thermal treatment (at 500° C or higher). This heat treatment is disclosed to serve multiple functions simultaneously: it crystallizes the amorphous layer into a polycrystalline film, activates dopants within the layer, and facilitates diffusion of those dopants to form a p-n junction and passivate the cell surface, thereby increasing efficiency. (’074 Patent, Abstract; col. 2:5-23).
- Technical Importance: This approach aims to simplify manufacturing by using a single thermal step to achieve multiple structural and electrical improvements that previously required more complex processes. (’074 Patent, col. 1:36-42).
Key Claims at a Glance
- The complaint’s allegations center on independent claim 1. (Compl. ¶¶23, 31).
- Claim 1 Essential Elements:
- 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 about 500° C. or higher, which crystallizes the conductive/passivating layer and facilitates dopant diffusion through the interface passivation layer.
- Providing metallization as electrodes that directly contact the conductive/passivating layer after the thermal treatment, where the diffused dopant shortens charge carrier flow paths.
- The complaint notes that Defendant’s demand letter also references dependent claims 4 and 8. (Compl. ¶24).
U.S. Patent No. 9,666,732 - "High-efficiency solar cell structures and methods of manufacture"
- Patent Identification: U.S. Patent No. 9,666,732, “High-efficiency solar cell structures and methods of manufacture,” issued May 30, 2017. (Compl. ¶12).
The Invention Explained
- Problem Addressed: As a divisional of the '074 Patent, the '732 Patent addresses the same problem of manufacturing highly efficient solar cells in a cost-effective manner. (’732 Patent, col. 1:35-43).
- The Patented Solution: This invention details a specific method where an "amorphous silicon-containing compound" that includes both an "oxygen dopant" and a "conductive dopant" is deposited. A subsequent thermal treatment diffuses the oxygen dopant into the substrate to form an oxide layer (the interface passivation layer) while simultaneously diffusing the conductive dopant to facilitate electrical connection. This process is designed to create multiple functional layers from a single deposited compound and thermal step. (’732 Patent, Abstract; col. 16:38-53).
- Technical Importance: The method proposes an integrated manufacturing flow where the interface passivation layer is formed in situ from a precursor film during the same thermal step that activates the cell's electrical properties. (’732 Patent, col. 2:4-9).
Key Claims at a Glance
- The complaint’s allegations center on independent claim 1. (Compl. ¶38).
- Claim 1 Essential Elements:
- Providing a substrate.
- Providing an interface passivation layer and a passivating film, which comprises:
- Providing an amorphous silicon-containing compound (containing oxygen dopant and conductive dopant) over the substrate.
- Thermally treating the compound to diffuse the oxygen dopant to form an oxide layer (the interface passivation layer) and to diffuse the conductive dopant to facilitate electrical connection.
- Providing at least one electrode over the passivating film, where the conductive dopant provides direct electrical connection between the electrode and the substrate.
- The complaint asserts non-infringement of claims 2 through 9 based on the non-infringement of claim 1. (Compl. ¶39).
III. The Accused Instrumentality
Product Identification
- Plaintiff’s N-type TOPCon solar cells and solar modules, including those in the Shine® series line (the "Accused Products"). (Compl. ¶¶3, 19).
Functionality and Market Context
- The complaint cites a demand letter from Defendant, which provides the technical description of the Accused Products. The letter alleges the products are n-type TOPCon cells having an n-type silicon central substrate, an interface passivation "tunnel oxide layer," and a conductive/passivating layer of doped polysilicon. (Compl. ¶23).
- The core of the infringement allegation, as described in the complaint, is that the high efficiency and bifaciality of the Accused Products are achieved by heating the cell above 500° C, which allegedly causes dopant from the polysilicon layer to diffuse through the interface passivation layer, shortening charge carrier flow paths. (Compl. ¶23). An excerpt from the Demand Letter detailing this infringement theory is included in the complaint. (Compl. ¶23).
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 | The Accused Products have an n-type silicon central substrate. | ¶23 | col. 19:13 |
| depositing or growing at least one amorphous interface passivation layer over the substrate | The Accused Products have an interface passivation layer (or tunnel oxide layer) on the backside of the substrate. | ¶23 | col. 5:56-65 |
| 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 Accused Products have a conductive and passivating layer of doped poly-silicon deposited on the backside of the interface passivation layer. | ¶23 | col. 5:41-55 |
| 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... | The Accused Products are allegedly heated well above 500° C, which causes dopant from the poly silicon layer to be diffused through the interface passivation layer. | ¶23 | col. 19:20-28 |
| providing metallization as electrodes which directly contact the at least one conductive and passivating layer... wherein the dopant diffused... provides shortened charge carrier flow paths... | The Accused Products have electrodes connected to the backside of the conductive and passivating layer, and the diffusion of the dopant allegedly shortens charge carrier flow paths. | ¶23 | col. 19:29-36 |
’732 Patent Infringement Allegations
The complaint does not provide a detailed infringement theory for the ’732 patent equivalent to that provided for the ’074 patent. It states a general allegation of infringement from the Defendant (Compl. ¶19) and then presents its own specific non-infringement arguments (Compl. ¶38). The following table is constructed based on Plaintiff's denials, which outline the likely points of dispute.
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| ...providing an amorphous silicon-containing compound over an upper surface of the substrate, the compound comprising oxygen dopant and the conductive dopant | Defendant's infringement allegation, as inferred from Plaintiff's denial, is that the TOPCon process involves such a compound. | ¶¶19, 38 | col. 20:1-4 |
| thermally treating the amorphous silicon-containing compound to diffuse the oxygen dopant, at least in part, into the upper surface of the substrate to form an oxide layer... | Defendant's infringement allegation, as inferred from Plaintiff's denial, is that the TOPCon process uses this specific thermal diffusion mechanism. | ¶¶19, 38 | col. 20:5-12 |
| wherein the thermally treating also diffuses at least a portion of the conductive dopant throughout the interface passivation layer to facilitate electrical connection to the substrate | Defendant's infringement allegation, as inferred from Plaintiff's denial, is that the TOPCon thermal process also diffuses the conductive dopant as claimed. | ¶¶19, 38 | col. 20:13-17 |
| providing at least one electrode over the passivating film, wherein the conductive dopant... provides direct electrical connection between the at least one electrode and the substrate | Defendant's infringement allegation, as inferred from Plaintiff's denial, is that the Accused Products' electrodes have a direct electrical connection as claimed. | ¶¶19, 38 | col. 20:18-22 |
- Identified Points of Contention:
- Technology Mismatch: Plaintiff alleges that the patents-in-suit are directed to HJT solar cells, while the Accused Products are TOPCon cells, and that the patents do not disclose or claim methods for manufacturing TOPCon cells. (Compl. ¶¶13, 17-18). The core of the case may turn on whether the claimed methods are technologically specific to HJT or are broad enough to cover TOPCon manufacturing.
- Functional Questions ('074 Patent): Plaintiff specifically denies that its manufacturing method performs the claimed thermal treatment step that results in crystallization and dopant diffusion as claimed, or the claimed metallization step. (Compl. ¶31). This raises the factual question of what function the heating step in Plaintiff's TOPCon process actually performs and whether it is equivalent to the function required by the claim.
- Technical Questions ('732 Patent): Plaintiff denies performing the thermal treatment step that diffuses an "oxygen dopant" to form an oxide layer. (Compl. ¶38). A central evidentiary question will be whether Plaintiff’s process for forming its tunnel oxide layer uses the specific mechanism of diffusing an oxygen dopant from a precursor film, as required by claim 1 of the ’732 Patent.
V. Key Claim Terms for Construction
For the ’074 Patent:
- The Term: "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"
- Context and Importance: This term is critical because infringement hinges on whether the heating step in Plaintiff's TOPCon process meets both the temperature and the functional requirements of the claim. Practitioners may focus on this term because Plaintiff explicitly denies its process performs these functions. (Compl. ¶31).
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The patent summary broadly mentions using a "thermal treatment greater than 500° C. in order to activate doping atoms in the compound and result in diffusion of dopant atoms into a substrate wafer." (’074 Patent, col. 2:18-22). This could support an argument that any high-temperature treatment causing diffusion falls within the scope.
- Evidence for a Narrower Interpretation: The claim language itself links the thermal treatment to the specific result of "crystallizing...the at least one conductive and passivating layer." The specification repeatedly describes turning "amorphous silicon layers" into "polycrystalline silicon layers" via thermal treatment. (’074 Patent, col. 16:2-8). Plaintiff may argue this context limits the claim to processes where crystallization of an initially amorphous layer is a required outcome, which may differ from the purpose of annealing in a standard TOPCon flow.
For the ’732 Patent:
- The Term: "thermally treating the amorphous silicon-containing compound to diffuse the oxygen dopant... to form an oxide layer"
- Context and Importance: The viability of the infringement claim against the Accused Products likely depends entirely on whether Plaintiff's process uses this highly specific mechanism. Plaintiff's denial of this step suggests it is a central point of dispute. (Compl. ¶38).
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The complaint does not provide sufficient detail for analysis of arguments for a broader interpretation.
- Evidence for a Narrower Interpretation: The claim language is highly specific, requiring diffusion of an "oxygen dopant" from a deposited "amorphous silicon-containing compound" to form the oxide layer. The specification explains this as an integrated process where a single deposited film "can split into two (or more) layers" upon heating. (’732 Patent, col. 16:38-42). This suggests the claim is tied to this specific in situ formation mechanism, which Plaintiff will likely argue is distinct from its own process for creating a tunnel oxide layer.
VI. Other Allegations
- Indirect Infringement: Plaintiff seeks a declaratory judgment of non-infringement for both direct and indirect infringement. (Compl., p. 8, Prayer for Relief ¶A-B). However, the complaint does not detail any specific factual allegations made by Defendant that would support claims of induced or contributory infringement.
- Willful Infringement: The complaint does not allege that Defendant has asserted willful infringement. However, the basis for a potential future willfulness claim is established by the Defendant’s alleged pre-suit knowledge communications, including a July 19, 2024 press release announcing its enforcement intentions and the April 1, 2025 demand letter. (Compl. ¶¶19-22).
VII. Analyst’s Conclusion: Key Questions for the Case
- A core issue will be one of technological scope: Can the claims of the patents-in-suit, which Plaintiff characterizes as being directed to HJT cell manufacturing, be construed broadly enough to read on the accused TOPCon manufacturing process? This will likely involve claim construction disputes over terms like "amorphous interface passivation layer" versus a "tunnel oxide layer."
- A key evidentiary question will be one of functional and mechanistic equivalence: Does the thermal processing step in Plaintiff's TOPCon manufacturing method perform the same specific functions (e.g., crystallization, dopant diffusion) as required by claim 1 of the '074 patent? Further, does the process for forming the oxide layer in the Accused Products rely on the diffusion of an "oxygen dopant" as explicitly required by claim 1 of the '732 patent, or is there a fundamental mismatch in the underlying physical mechanism?