Mundra Solar v. First Solar, Inc.

This case involves an intricate interplay between patent infringement litigation in district court and validity challenges at the Patent Trial and Appeal Board (PTAB). The primary parties are Mundra Solar, an Indian solar photovoltaic manufacturer, and First Solar, Inc., an American solar technology and manufacturing company.

Mundra Solar PV Limited, the solar manufacturing arm of the Adani Group, is India's largest vertically integrated solar PV manufacturer, producing high-efficiency modules such as TOPCon, MonoPERC, Bifacial, and Dual Glass technologies. First Solar, Inc., headquartered in Arizona, is a leading global manufacturer of thin-film photovoltaic (PV) modules, primarily using cadmium telluride (CdTe) technology, but also holds a patent portfolio related to Tunnel Oxide Passivated Contact (TOPCon) crystalline silicon solar cells. The dispute centers on First Solar's TOPCon technology, with Mundra Solar's N-type TOPCon "Shine®" series solar modules and their manufacturing processes being the allegedly infringing technology.

The patents at issue are U.S. Patent No. 9,130,074 and U.S. Patent No. 9,666,732, both titled "High-efficiency solar cell structures and methods of manufacture." These patents generally describe advanced solar cell designs and specific manufacturing methods, particularly for TOPCon crystalline silicon photovoltaic cells. U.S. Patent No. 9,130,074 details solar cells including a central substrate, conductive layers, anti-reflection layers, passivation layers, and electrodes, along with manufacturing methods like single-side CVD deposition and thermal treatment. U.S. Patent No. 9,666,732 further specifies methods involving depositing an amorphous, silicon-containing compound and applying thermal treatment above 500°C to activate doping atoms, thereby creating junctions or crystallizing passivating layers. The procedural posture involves parallel proceedings: First Solar filed patent infringement lawsuits in the U.S. District Court for the District of Delaware against Mundra Solar and other manufacturers. Mundra Solar PV Limited, in turn, filed a pre-emptive declaratory judgment action in the District of Delaware (Case No. 1:25-cv-00462) on April 15, 2025, seeking a declaration of non-infringement, to which First Solar responded with infringement counterclaims. Simultaneously, Mundra Solar filed Inter Partes Review (IPR) petitions at the U.S. Patent Trial and Appeal Board (PTAB) challenging the validity of U.S. Patent Nos. 9,130,074 and 9,666,732, with the petition challenging U.S. Patent No. 9,666,732 specifically identified as IPR2025-01411. However, public reports indicate that while Mundra Solar specifically challenged U.S. Patent No. 9,666,732, U.S. Patent No. 9,130,074 was challenged in separate IPRs by other parties. The PTAB denied institution of Mundra Solar's petition(s) on December 18, 2025, with the public announcement of the denials occurring on January 20, 2026, thereby maintaining the validity of the patents.

This case is notable for several reasons within the solar energy industry and patent landscape. It signifies First Solar's aggressive strategy to enforce its TOPCon patent portfolio, which it acquired through TetraSun in 2013, against competitors in the crystalline silicon solar cell market, even though First Solar is predominantly known for its thin-film technology. The dispute is part of a broader global intellectual property battle impacting the supply chain for high-efficiency solar cells, particularly given the context of U.S. tariffs on Chinese solar products and the rising prominence of Indian manufacturers like Mundra Solar. The PTAB's discretionary denial of institution for Mundra Solar's IPR petitions, along with similar petitions from other solar manufacturers, is particularly significant. These denials were based, in part, on the PTAB's "settled expectations" doctrine and the existence of parallel district court litigation, underscoring the USPTO's evolving approach to managing IPRs in the presence of ongoing infringement suits and the age of the challenged patents.

The legal proceedings involving Mundra Solar and First Solar include both a parallel patent infringement lawsuit in the U.S. District Court for the District of Delaware and an Inter Partes Review (IPR) petition at the U.S. Patent Trial and Appeal Board (PTAB).

Key Legal Developments and Outcome:

1. Initiation of Patent Enforcement & Infringement Litigation

• July 2024: First Solar announced its intention to license and enforce its Tunnel Oxide Passivated Contact (TOPCon) technology patent portfolio, subsequently initiating infringement investigations against several crystalline silicon solar cell manufacturers.
• April 15, 2025: A patent infringement lawsuit, captioned Mundra Solar PV Limited v. First Solar, Inc., Case No. 1:25-cv-00462, was filed in the U.S. District Court for the District of Delaware. In this litigation, First Solar is asserting its U.S. Patent No. 9,666,732 against Mundra Solar and related entities.
• August 1, 2025: First Solar filed its Answer to the Complaint and asserted Counterclaims against Mundra Solar PV Limited, Adani Solar, Mundra Solar Energy Ltd., Adani Solar USA Inc., and Adani Solar USA LLC in the Delaware district court case.
• September 23, 2025: Mundra Solar PV Limited filed its Answer to First Solar's Counterclaims in the ongoing district court litigation.

2. Parallel PTAB IPR Proceeding

• Mid-2025: Mundra Solar filed an Inter Partes Review (IPR) petition challenging the validity of First Solar's U.S. Patent No. 9,666,732 before the U.S. Patent Trial and Appeal Board (PTAB). This patent, along with U.S. Patent No. 9,130,074, relates to methods of manufacturing TOPCon crystalline silicon photovoltaic solar cells.
• December 18, 2025: The Director of the USPTO issued a discretionary denial of Mundra Solar's IPR petition against U.S. Patent No. 9,666,732. This decision was based on the "Settled Expectations" doctrine, which considers the length of time a patent has been in force (Patents 9,130,074 and 9,666,732 were issued in 2015 and 2017, respectively) before a challenge is initiated.
• January 20, 2026: First Solar publicly announced that the USPTO had denied institution of IPR petitions filed by Mundra Solar, JinkoSolar, and Canadian Solar, thereby upholding the validity of its TOPCon technology patents.

3. Present Posture of the Litigation

• Ongoing District Court Litigation: The patent infringement lawsuit in the District of Delaware (C.A. No. 1:25-cv-00462) remains active.
  • January 19, 2027: A Claim Construction (Markman) Hearing is scheduled.
  • May 8, 2028: A Jury Trial is scheduled.
• PTAB Outcome: The IPR proceeding initiated by Mundra Solar concluded with the denial of institution, meaning the PTAB did not proceed to review the merits of the invalidity challenge against U.S. Patent No. 9,666,732. This decision leaves the patent's validity intact as far as that specific IPR challenge is concerned.

Counsel of record representing Mundra Solar in Mundra Solar PV Limited v. First Solar, Inc., Case No. 1:25-cv-00462 in the U.S. District Court for the District of Delaware, include:

• Shamita Etienne-Cummings

  • Role: Counsel (admitted pro hac vice)
  • Firm & Office: Womble Bond Dickinson (US) LLP, Boston, MA
  • Experience Note: Focuses on patent and other intellectual property litigation across various technologies, including medical devices, electronics, and software.

• James P. Gagen

  • Role: Counsel (admitted pro hac vice)
  • Firm & Office: Womble Bond Dickinson (US) LLP, Boston, MA
  • Experience Note: Represents clients in patent litigation in federal district courts and before the PTAB, particularly in the electrical and computer technologies sectors.

• Stephanie Adamakos

  • Role: Counsel (admitted pro hac vice)
  • Firm & Office: Womble Bond Dickinson (US) LLP, Boston, MA
  • Experience Note: Specializes in patent litigation, inter partes review proceedings, and other intellectual property disputes, often involving electrical and computer technologies.

• Karen Keller

  • Role: Local Counsel
  • Firm & Office: Shaw Keller LLP, Wilmington, DE
  • Experience Note: A highly experienced litigator, often serving as Delaware local counsel in complex patent and corporate litigation in the District of Delaware and the Delaware Court of Chancery.

Counsel of Record for Defendant First Solar, Inc.

First Solar, Inc., as the defendant in the patent infringement lawsuit Mundra Solar PV Limited v. First Solar, Inc., Case No. 1:25-cv-00462, in the U.S. District Court for the District of Delaware, is represented by lead counsel from Cravath, Swaine & Moore LLP and local counsel from Potter Anderson & Corroon LLP.

Here are the identified attorneys:

1. Keith R. Hummel

• Role: Lead Counsel
• Firm: Cravath, Swaine & Moore LLP.
• Office Location: New York, NY.
• Experience Note: Keith R. Hummel is identified as lead counsel for First Solar in multiple district court litigations involving the asserted patents, including the case against Mundra Solar. His firm, Cravath, Swaine & Moore LLP, is a prominent firm with significant experience in complex litigation.

2. Sharonmoyee Goswami

• Role: Counsel
• Firm: Cravath, Swaine & Moore LLP.
• Office Location: New York, NY.
• Experience Note: Sharonmoyee Goswami is listed as counsel for First Solar (Patent Owner) in related PTAB IPR proceedings involving the same patents at issue, indicating her involvement in the overall strategy for First Solar's patent portfolio.

3. David E. Moore

• Role: Local Counsel (Delaware)
• Firm: Potter Anderson & Corroon LLP, Wilmington, DE.
• Experience Note: David E. Moore is the Chair of Potter Anderson's Litigation Group and has extensive experience serving as Delaware counsel in complex patent infringement litigation, including high-stakes cases in the U.S. District Court for the District of Delaware. Potter Anderson & Corroon LLP is consistently recognized for its intellectual property litigation practice in Delaware.

4. Bindu Palapura

• Role: Local Counsel (Delaware)
• Firm: Potter Anderson & Corroon LLP, Wilmington, DE.
• Experience Note: Bindu Palapura is a senior associate at Potter Anderson & Corroon LLP who has served as Delaware counsel in significant patent infringement suits in the District of Delaware.

This list is based on available public information, including filings in related PTAB proceedings that identify lead counsel for First Solar in the district court action, and typical local counsel appearances in the District of Delaware. The specific appearances of each attorney in the Delaware district court docket for this exact case would confirm their precise roles.