US 9666732

Here's a concise summary of US Patent 9666732:

Title: High-efficiency solar cell structures and methods of manufacture
Assignee: First Solar Inc
Inventors: Oliver Schultz-Wittmann, Denis DeCEUSTER
Filing Date: August 19, 2015
Issue Date: May 30, 2017

Abstract:
The patent discloses solar cells of varying composition, generally comprising a central substrate, conductive layer(s), antireflection layers(s), passivation layer(s), and/or electrode(s). It highlights multifunctional layers that combine functions such as passivation, transparency, sufficient conductivity for vertical carrier flow, the junction, and varying degrees of anti-reflectivity. Improved manufacturing methods are also described, including single-side Chemical Vapor Deposition (CVD) processes and thermal treatment for layer formation and/or conversion.

Plain-Language Overview of Independent Claims:

The patent contains several independent claims covering both solar cell structures and methods of manufacturing them. Based on the provided patent text, the key independent claims focus on the combination of layers and manufacturing processes for high-efficiency solar cells.

• Independent Method Claim (from Summary of the Invention):
  One aspect of the invention covers a method for fabricating solar cell structures. This method includes providing a wafer as a central substrate, followed by the deposition or growth of interface passivation layers over the substrate. Subsequently, conductive layers are deposited over the passivation layers, and a thermal treatment is applied. The method also allows for optional deposition of antireflective layers (which may include back-side mirrors) and the provision of metallization to form electrodes.

• Independent Method Claim (Multifunctional Film):
  Another independent claim describes a method that involves applying a heat treatment to produce a multifunctional film. This film then separates into a surface passivating interface layer and a highly doped polycrystalline passivation layer with high transparency.

• Independent Method Claim (Crystallization):
  A further independent claim focuses on a method that includes depositing an amorphous, silicon-containing compound. A heat treatment is then used to initiate the crystallization of this compound into a polycrystalline film.

• Independent Method Claim (Optical Transmissivity):
  Another independent method claim details depositing an amorphous, silicon-containing compound and subsequently using a heat treatment that not only leads to the crystallization of the film but also increases its optical transmissivity.

• Independent Method Claim (Doping Activation):
  An independent claim covers depositing an amorphous, silicon-containing compound and then using a heat treatment to activate doping atoms within the compound.

• Independent Method Claim (High-Temperature Doping and Diffusion):
  One embodiment of the invention comprises depositing an amorphous, silicon-containing compound and applying a thermal treatment greater than 500° C. This treatment activates doping atoms in the compound and results in the diffusion of these dopant atoms into a substrate wafer to create either a high-low junction or a p-n junction.

CAFC 2026 Dockets:
A search of the CAFC 2026 dockets did not return any specific cases or mentions of US patent 9666732 as of April 26, 2026. The available scheduled cases for April, May, and June 2026 do not list this patent number.

As a patent attorney, I have identified the following known litigation involving US Patent 9666732:

1. PTAB Case IPR2025-01411

• Plaintiff(s): Unified Patents
• Defendant(s): Not explicitly stated, but typically the patent owner (First Solar Inc. or its predecessors at the time of filing).
• Jurisdiction: Patent Trial and Appeal Board (PTAB)
• Case Number: IPR2025-01411
• Filing Date: Not explicitly stated, but the case was "filed (Not Instituted - Procedural)" in 2025.
• Outcome or Current Status: Not Instituted - Procedural.

2. US Case filed in Delaware District Court

• Plaintiff(s): Not explicitly stated, but the patent was reassigned to First Solar Inc. in February 2025 and then to JPMORGAN CHASE BANK, N.A. in September 2025 via a patent security agreement.
• Defendant(s): Not explicitly stated.
• Jurisdiction: Delaware District Court
• Case Number: 1:25-cv-00462
• Filing Date: Not explicitly stated, but the case was filed in the Delaware District Court, and an entry indicates a filing date in 2025.
• Outcome or Current Status: The case is listed as "litigation" and "Critical".

Proceedings overview

There is one AIA trial proceeding on file for US Patent 9666732, with a status of Discretionary Denial. This indicates the patent's claims have not been substantively challenged and remain intact, presenting a stronger defensive posture for the patent owner against future challenges based on the grounds that could have been raised in this petition.

IPR2025-01411 — Mundra Solar PV Limited v. Tetrasun Inc

• Type: Inter Partes Review
• Filed: 2025-08-15
• Status: Discretionary Denial – The PTAB declined to institute the IPR.
• Judge panel: Not publicly available from the provided data.
• Petition grounds: Not publicly available from the provided data.
• Institution decision: Denied. The petition was denied institution on 2026-01-13. The reason for the denial was procedural, specifically a Discretionary Denial.
• Final Written Decision: Not applicable, as institution was denied.
• Settlement / termination: Not applicable, as institution was denied.
• Appeal: Not applicable, as institution was denied.
• Defensive value: The patent owner successfully fended off an IPR challenge on procedural grounds. This means the claims of US9666732 have not been substantively reviewed by the PTAB in this proceeding, and an IPR-based defense using the same or similar grounds would likely face the same discretionary denial.

Strategic summary

Currently, all claims of US9666732 remain UNTESTED by a full PTAB trial. The single IPR filed, IPR2025-01411, was denied institution on discretionary grounds, meaning the merits of the patentability challenge were not evaluated. This leaves all claims of the patent, as issued, in full force.

The estoppel landscape is relatively clear. While a discretionary denial can involve various factors, if the denial was based on factors that could reasonably have been foreseen or addressed by the petitioner, subsequent petitioners (and their privies) might face an uphill battle trying to institute an IPR on the same or substantially similar prior art or arguments. However, the exact grounds raised in the petition are not public, so the full scope of potential estoppel is unclear.

The involvement of Unified Patents as a source for litigation and PTAB data signals that they are monitoring the patent. Their listing of IPR2025-01411 with a "Not Instituted - Procedural" status suggests an interest in patent quality or defensive aggregation, although they are listed as a source of information rather than the petitioner in the provided PTAB data. Mundra Solar PV Limited was the petitioner in IPR2025-01411.

Recommended next steps

If you are a defendant facing assertion of US9666732, you should note that no claims have been invalidated by the PTAB. The denial of IPR2025-01411 on discretionary grounds suggests that a strong procedural argument was successfully made by the patent owner. Any new IPR petition would need to carefully consider the reasons for the prior discretionary denial to avoid a similar outcome.

The PTAB case IPR2025-01411 was denied institution on 2026-01-13. Details of the discretionary denial can be found on the USPTO PTAB Decisions portal by searching for IPR2025-01411.

Inventors

• Oliver Schultz-Wittmann: Tetrasun Inc.
• Denis DeCEUSTER: Tetrasun Inc.

It is noted that both inventors remained with Tetrasun Inc. at the time of the initial assignment, showing no immediate departure pattern.

Original assignee

The original assignee named on the issued patent is Tetrasun Inc. Based on available information, Tetrasun Inc. was a solar cell technology company. Its current status is acquired by First Solar Inc..

Assignment timeline

• 2015-08-19 (executed) / recorded 2015-08-19

  • Conveyance: Assignment
  • Assignor: DECEUSTER, DENIS; SCHULTZ-WITTMANN, OLIVER
  • Assignee: TETRASUN, INC.
  • Correspondent: Not recorded.
  • Context: Original assignment from inventors to the filing entity.

• 2025-02-24 (executed) / recorded 2025-02-24

  • Conveyance: Assignment
  • Assignor: TETRASUN, INC.
  • Assignee: FIRST SOLAR, INC.
  • Correspondent: Not recorded.
  • Context: Acquisition of Tetrasun Inc. or its assets by First Solar Inc.

• 2025-09-11 (executed) / recorded 2025-09-11

  • Conveyance: Patent Security Agreement
  • Assignor: FIRST SOLAR INC.
  • Assignee: JPMORGAN CHASE BANK, N.A.
  • Correspondent: Not recorded.
  • Context: Securitization of the patent as collateral for financing.

Timeline diagram

timeline
    title Ownership of US 9666732
    2015 : Inventors to Tetrasun Inc
    2017 : Issued
    2025 : Tetrasun Inc to First Solar Inc
         : First Solar Inc to JPMorgan Chase Bank

NPE / troll-pattern signals

1. Shell-entity transfer — Not present. The transfers are to known operating companies (Tetrasun, First Solar) or a financial institution (JPMorgan Chase Bank) for securitization.
2. Known asserter in the chain — Not present. Neither Tetrasun Inc., First Solar Inc., nor JPMorgan Chase Bank, N.A. are identified as known NPEs in public lists.
3. Repeat correspondent across the chain — Unclear. The correspondent information is not available in the provided legal event history for any of the assignments.
4. Cascading transfers — Not present. There are two assignments and one security agreement over a 10-year period, which does not indicate cascading transfers. The two assignments and the security agreement are spaced out.
5. Pre-litigation transfer — Unclear. While a US case was filed in Delaware District Court (1:25-cv-00462) in 2025, the exact filing date is not provided, making it difficult to definitively assess if the transfer to First Solar Inc. (February 2025) or the security agreement with JPMorgan Chase Bank (September 2025) occurred within 6 months before the first infringement suit was filed.
6. Bankruptcy fire-sale — Not present. There is no indication of bankruptcy proceedings for Tetrasun Inc. or First Solar Inc. related to the patent transfers.
7. Privateering — Not present. There is no evidence in the provided information to suggest privateering.
8. Defensive aggregator (anti-NPE) — Not present. The chain does not terminate at a known defensive aggregator.

Verdict

Operating-company assertion The patent was assigned from the original inventor-founded company (Tetrasun Inc.) to First Solar Inc., a known operating company in the solar industry. The subsequent security agreement with JPMorgan Chase Bank, N.A. is a common financial arrangement for operating companies. While litigation is noted, it appears to involve an operating company as the patent owner.

USPTO Assignment Center search page: https://assignmentcenter.uspto.gov/

To identify the most relevant prior art for US patent 9666732, I will examine the patent citations listed in the patent itself.

The publication date of US9666732B2 is May 30, 2017, and its filing date is August 19, 2015.

Here are some of the most relevant prior art references cited in US9666732B2, along with their publication/filing dates, a brief description, and which claims they potentially anticipate:

1. U.S. Provisional Application No. 61/171,194

• Full Citation: U.S. Provisional Application entitled "High-Efficiency Solar Cell Structures and Methods of Manufacture," filed Apr. 21, 2009, and assigned application No. 61/171,194.
• Publication/Filing Date: April 21, 2009
• Brief Description: This is the foundational provisional application from which US9666732B2 claims benefit. It covers high-efficiency solar cell structures and methods of manufacture.
• Potential Anticipation: This provisional application likely anticipates all claims of US9666732B2, as it serves as the priority document and contains the initial disclosure of the invention.

2. U.S. Ser. No. 13/265,462

• Full Citation: U.S. Ser. No. 13/265,462, filed Oct. 20, 2011, entitled “High-Efficiency Solar Cell Structures and Methods of Manufacture”.
• Publication/Filing Date: October 20, 2011
• Brief Description: This is a divisional application of U.S. Ser. No. 13/265,462, which itself claims benefit from the provisional application 61/171,194. It also describes high-efficiency solar cell structures and methods of manufacture.
• Potential Anticipation: As a direct lineage application, it likely anticipates all claims, similar to the provisional application, as it is part of the same patent family and continues the prosecution of the disclosed subject matter.

3. U.S. Provisional Application No. 61/171,187

• Full Citation: U.S. Provisional Application entitled “Method for Forming Structures in a Solar Cell,” filed 21 Apr. 2009 and assigned application No. 61/171,187.
• Publication/Filing Date: April 21, 2009
• Brief Description: This provisional application focuses on methods for forming structures in a solar cell, including metallization techniques. The patent states that metallization for any of its disclosed structures can be formed in accordance with this application.
• Potential Anticipation: This reference could potentially anticipate claims related to the methods of metallization and the formation of specific structures within the solar cell, particularly any claims describing the formation of conductive contacts or patterns (e.g., those involving laser ablation or localized laser-assisted conversion of functional films).

4. International Patent Application No. PCT/US2010/123976

• Full Citation: Commonly-assigned, co-filed International Patent Application entitled “Method for Forming Structures in a Solar Cell,” assigned application number PCT/US2010/123976.
• Publication/Filing Date: Not explicitly stated as a separate filing date in the provided text, but co-filed with the U.S. Provisional Application No. 61/171,187. The priority date for related PCT/US2010/031869 is April 21, 2009.
• Brief Description: This international application details methods for forming structures in solar cells, including specific metallization techniques, which are incorporated by reference into US9666732B2.
• Potential Anticipation: Similar to the provisional application 61/171,187, this PCT application could anticipate claims related to metallization methods and the formation of conductive contact patterns.

5. U.S. Provisional Application No. 61/171,491

• Full Citation: U.S. Provisional Application entitled “Localized Metal Contacts By Localized Laser Assisted Reduction Of Metal-Ions In Functional Films, And Solar Cell Applications Thereof,” filed 22 Apr. 2009 and assigned application No. 61/171,491.
• Publication/Filing Date: April 22, 2009
• Brief Description: This provisional application focuses on forming localized metal contacts using laser-assisted reduction of metal-ions in functional films for solar cell applications.
• Potential Anticipation: This reference could potentially anticipate claims related to methods of forming electrical contacts in a solar cell layer by selectively modifying material upon laser irradiation, and where a remaining region forms a functional layer.

6. International Patent Application No. PCT/US2010/031881

• Full Citation: Commonly-assigned, co-filed International Patent Application entitled “Localized Metal Contacts By Localized Laser Assisted Conversion Of Functional Films In Solar Cells,” assigned application number PCT/US2010/031881.
• Publication/Filing Date: Not explicitly stated as a separate filing date in the provided text, but co-filed with the U.S. Provisional Application No. 61/171,491. The priority date for related PCT/US2010/031869 is April 21, 2009.
• Brief Description: This international application describes forming localized metal contacts through laser-assisted conversion of functional films in solar cells.
• Potential Anticipation: Similar to the provisional application 61/171,491, this PCT application could anticipate claims directed to methods of forming localized electrical contacts using laser-assisted conversion.

It's important to note that the patent itself states that "Each of these Applications is hereby incorporated by reference herein in its entirety," indicating that their content is considered part of the disclosure of US9666732B2. This would mean they are highly relevant for a 35 U.S.C. § 102 anticipation analysis.

Obviousness Analysis of US Patent 9666732 under 35 U.S.C. § 103

To determine the obviousness of US Patent 9666732, we must consider whether the differences between the claimed invention and the prior art would have been obvious, at the time the invention was made, to a person having ordinary skill in the art (PHOSITA). This analysis follows the framework set forth in Graham v. John Deere Co., which considers the scope and content of the prior art, the differences between the prior art and the claims, the level of ordinary skill in the art, and secondary considerations of non-obviousness. The Supreme Court's decision in KSR Int'l Co. v. Teleflex Inc. further clarified that a motivation to combine prior art references is crucial and can be gleaned from various sources, including common sense, market pressure, and the desire to improve existing products or processes, even if not explicitly stated in the references themselves.

The patent US9666732 focuses on high-efficiency solar cell structures and methods of manufacture, including multifunctional layers and thermal treatments for layer formation and conversion. The priority date for US9666732 is April 21, 2009.

Prior Art References

The "Prior art keywords" listed in US9666732 include "silicon," "type," "doped," "layer," and "layers." The patent itself incorporates by reference U.S. Provisional Application No. 61/171,187, filed April 21, 2009, and PCT/US2010/123976, both related to "Method for Forming Structures in a Solar Cell," and U.S. Provisional Application No. 61/171,491, filed April 22, 2009, and PCT/US2010/031881, concerning "Localized Metal Contacts By Localized Laser Assisted Conversion Of Functional Films In Solar Cells." These references, while related to the applicant's own work, establish a baseline of knowledge in the art at or before the priority date.

Furthermore, a general understanding of solar cell technology at the time would include:

• Solar cells with various layers: The general concept of solar cells comprising a central substrate, conductive layers, antireflection layers, passivation layers, and electrodes was well-known.
• Surface Passivation: The importance of surface passivation to suppress electron and hole recombination was recognized. Dielectric layers (e.g., silicon oxide, silicon nitride) and intrinsic amorphous silicon were known for this purpose.
• Doping for junctions: The use of doping atoms to create high-low junctions or p-n junctions for carrier collection was a standard technique in semiconductor devices, including solar cells.
• Transparent Conductive Oxides (TCOs): Materials like indium tin oxide (ITO), aluminum-doped zinc oxide, and fluorine-doped tin oxide were established as transparent and conductive films for solar cell electrodes.
• CVD processes: Various Chemical Vapor Deposition (CVD) methods (PECVD, APCVD, LPCVD) were common for depositing layers in semiconductor manufacturing.
• Thermal treatment: Heat treatments were used in semiconductor fabrication for various purposes, including activating dopants, crystallizing amorphous films into polycrystalline films, and improving optical transmissivity. For example, US Patent 7,666,732 B2 (Doris et al., filed Sep. 15, 2008) describes thermal treatments in CMOS fabrication, indicating the general knowledge of such processes in semiconductor manufacturing. While Doris et al. is not directly in the solar cell art, it demonstrates the broader knowledge of thermal processing in semiconductor device manufacturing.

Obviousness Combinations and Motivations

A PHOSITA in the field of solar cell manufacturing, seeking to improve efficiency and reduce manufacturing complexity, would have been motivated to combine known elements and processes in predictable ways.

1. Combination of known layers and doping techniques with thermal treatment for crystallization and dopant activation (Claim 3 and related method claims):

• Prior Art Elements: The prior art clearly teaches solar cells with various layers, including a substrate, passivation layers, and conductive layers (e.g., layers 62, 63, 64, 65, 66, 67, 68 in FIG. 6 of US9666732). It also teaches the use of amorphous silicon-containing compounds for layers, and the general application of thermal treatment in semiconductor manufacturing for activating dopants and crystallizing films.
• Motivation to Combine: A PHOSITA would be motivated to improve the electrical and optical properties of amorphous silicon-containing layers by crystallizing them into polycrystalline films and activating dopants. Crystallization can lead to improved carrier mobility and stability, while dopant activation is essential for forming efficient junctions and conductive layers. The patent itself notes that amorphous silicon layers can be turned into polycrystalline silicon layers by thermal treatment, and this process can also activate doping atoms. The desire to achieve "high-efficiency solar cell structures and methods of manufacture" and "increased cell efficiency" would provide a strong motivation to apply known thermal treatments to amorphous silicon-containing layers to optimize their performance.
• Obviousness Argument: Combining the known practice of depositing amorphous, silicon-containing compounds in solar cells with the known technique of using heat treatment to initiate crystallization and activate doping atoms would have been obvious to a PHOSITA. The expected result would be improved electrical and optical properties, leading to higher efficiency, a well-understood goal in the art. The patent explicitly states that thermal treatment "may activate doping atoms in the compound and result in diffusion of dopant atoms into a substrate wafer to provide a high-low junction or a p-n junction." This describes a predictable application of known techniques to achieve a desired outcome in solar cell fabrication.

2. Combination of separate passivation and conductive layers into a multifunctional layer via heat treatment (Claims related to multifunctional films, e.g., layers 93a, 97a):

• Prior Art Elements: The patent explicitly states that "Multifunctional layers provide combined functions of passivation, transparency, sufficient conductivity for vertical carrier flow, the junction, and/or varying degrees of anti-reflectivity." The prior art would have included individual layers for passivation (e.g., silicon oxide, silicon nitride, intrinsic amorphous silicon), transparency, conductivity (e.g., TCOs, doped silicon), and antireflection.
• Motivation to Combine: A PHOSITA would be motivated to simplify manufacturing processes and potentially enhance performance by combining the functions of multiple layers into a single "multifunctional film." The patent highlights that "high-volume manufacturing is generally considered to attain a high degree of cost-effectiveness and efficiency if the number of manufacturing steps, and the complexity of each step, can be minimized." This provides a clear motivation to reduce the number of distinct layers if possible. The patent also teaches that a layer deposited in a single process can "split into two (or more) layers" during thermal treatment, for example, incorporating oxygen in an amorphous deposited layer to form a thin oxide at the silicon interface while the rest crystallizes and dopants activate.
• Obviousness Argument: Given the motivation to reduce manufacturing steps and improve efficiency, a PHOSITA would have sought ways to achieve multiple functions with fewer layers. The idea of using a thermal treatment to induce a single deposited film to form both a passivating interface and a doped polycrystalline layer (as described in the patent) would be an obvious solution, especially if the starting amorphous silicon-containing compounds are known to be capable of such transformation and contain necessary doping elements or oxygen. This is a predictable outcome of optimizing film deposition and annealing processes. The specific examples provided in the patent for multifunctional layers, such as n-type amorphous or polycrystalline silicon carbides/nitrides, silicon, and diamond-like carbon, indicate that these are known materials capable of being doped and formed into various structures.

3. Integration of embedded electrodes for stress reduction (Claims related to FIGS. 16 and 17):

• Prior Art Elements: The patent introduces solar cells with metal electrodes embedded in a glass or other laminating films that are compressed or bonded to the cell. The electrodes make contact on top of the outer layers without penetrating underlying layers. The prior art for solar cells would include traditional metallization directly deposited onto the cell.
• Motivation to Combine: The patent explicitly states that embedding electrodes in glass or laminating films "has the benefit that the metal does not need to be deposited directly onto the cell itself, thereby eliminating a typical source of film stress which can cause cell bowing." This is particularly useful for "very large area wafers, such as thin-film silicon sheets and/or very thin wafers." A PHOSITA would be motivated to address known manufacturing challenges such as film stress and bowing, especially as solar cells become larger and thinner. Improving the "manufacturing in a cost effective manner" would lead a PHOSITA to consider alternative, less stressful contact methods.
• Obviousness Argument: The problems of film stress and cell bowing in thin-film or large-area solar cells would have been well-known to a PHOSITA. Seeking methods to mitigate these issues, a PHOSITA would have considered alternative electrode application techniques that avoid direct deposition and its associated stress. The concept of using pre-formed electrodes embedded in a laminating material, which then contact the cell surface upon bonding, would be an obvious solution given the desire to reduce stress and improve manufacturing yield for large, thin wafers. The use of "anisotropic conducting films (ACF), conductive epoxies, or spring-like contact probes" to enhance electrical conductivity between embedded electrodes and outer layers is also a collection of known conductive interfacing solutions.

In summary, the advancements claimed in US9666732, while contributing to solar cell efficiency and manufacturing, appear to stem from predictable combinations and optimizations of existing solar cell components and fabrication techniques. The motivations for these combinations are clearly articulated within the patent itself, focusing on increased efficiency, reduced manufacturing complexity, and addressing known issues like film stress.