US 11824136

US patent 11824136, titled "Solar cell, manufacturing method thereof, and photovoltaic module," was issued on November 21, 2023, from an application filed on October 12, 2022. The current assignees are Zhejiang Jinko Solar Co Ltd and Jinko Green Energy Shanghai Management Co Ltd. The inventors are Kun Yu, Changming Liu, and Xinyu Zhang.

Abstract:
The patent describes a solar cell, a manufacturing method for it, and a photovoltaic module. The solar cell includes a semiconductor substrate with a first texture structure on its rear surface. This first texture structure has at least two partially stacked substructures. The distance between the top surface of an outermost substructure and an adjacent one is 2 μm or less, and the one-dimensional size of the outermost substructure's top surface is 45 μm or less. The solar cell also features a first passivation layer on its front surface, a tunnel oxide layer on the first texture structure, a doped conductive layer on the tunnel oxide layer (with the same conductivity type as the substrate), and a second passivation layer on the doped conductive layer.

Independent Claims Overview:

• Independent Claim 1 (Solar Cell): This claim describes a solar cell comprising:

  • A semiconductor substrate with a "first texture structure" on its rear surface. This first texture structure is made of two or more "first substructures" that are at least partially stacked. The vertical distance between the top surface of the outermost substructure and an adjacent one is no more than 2 micrometers (μm), and the one-dimensional size of the outermost substructure's top surface is no more than 45 μm.
  • A first passivation layer on the front surface of the semiconductor substrate.
  • A tunnel oxide layer on the rear surface's first texture structure.
  • A doped conductive layer on the tunnel oxide layer, where its doping type matches that of the semiconductor substrate.
  • A second passivation layer on the doped conductive layer.

• Independent Claim 2 (Photovoltaic Module): This claim describes a photovoltaic module that includes multiple solar cell strings. Each of these strings is composed of the solar cells as described in Independent Claim 1.

• Independent Claim 3 (Method for Manufacturing a Solar Cell): This claim outlines a method for manufacturing a solar cell, including:

  • Texturing the front surface of a semiconductor substrate to form a "second texture structure" which includes pyramid-shaped microstructures.
  • Doping the front surface of the textured semiconductor substrate to create a doped layer.
  • Polishing the rear surface of the semiconductor substrate with an alkali solution to form a "first texture structure." Similar to Claim 1, this first texture structure includes at least two partially stacked "first substructures," with specific dimensional constraints (vertical distance between outermost and adjacent substructures ≤ 2 μm, one-dimensional size of outermost substructure's top surface ≤ 45 μm).
  • Forming a tunnel oxide layer on the first texture structure of the rear surface.
  • Depositing a polycrystalline silicon layer on the tunnel oxide layer and doping it to form a doped conductive layer, where the doping type matches that of the semiconductor substrate.
  • Forming a first passivation layer on the front surface of the semiconductor substrate.
  • Forming a second passivation layer on the surface of the doped conductive layer.

Legal Status and Litigation:
The patent is currently active. Its anticipated expiration date is August 27, 2041. The patent family is involved in litigation, with the first worldwide family litigation having been filed. A PTAB case, IPR2026-00230, has been filed and is currently pending. Additionally, US cases related to this patent family have been filed in the Texas Southern District Court and the California Northern District Court. No specific CAFC 2026 dockets directly addressing patent 11824136 have been identified as of April 26, 2026.

Known litigation involving US patent 11824136 is as follows:

1. District Court Litigation (Infringement)

   • Plaintiff(s): JinkoSolar (specifically, Shanghai Jinko Green Energy Enterprise Management Co LTD and Zhejiang Jinko Solar Co LTD).
   • Defendant(s):
     • VSUN Solar USA Inc., Toyo Co. Ltd., Abalance Corporation, WWB Corporation, and Fuji Solar Co., Ltd. (California case).
     • Waaree Energies Limited, Waaree Solar Americas Inc. (Texas case).
   • Jurisdiction:
     • United States District Court for the Northern District of California.
     • United States District Court for the Southern District of Texas.
   • Case Number:
     • Not explicitly provided for the California case, but described as filed in December 2024.
     • 4:25-cv-00532 (Texas case).
   • Filing Date:
     • December 2024 (California case).
     • 2025-02-07 (Texas case).
   • Outcome or Current Status:
     • California case: As of April 17, 2025, VSUN and Toyo denied infringement and argued invalidity. Abalance and its subsidiaries filed a motion to dismiss for lack of jurisdiction and insufficient clarity in the complaint. The lawsuit would proceed against VSUN and Toyo if the motion to dismiss is granted for Abalance.
     • Texas case: "Proceeding" (진행중).

2. Patent Trial and Appeal Board (PTAB) Litigation (Inter Partes Review - IPR)

   • Petitioner(s): SEG Manufacturing Inc., New Energy Imports Inc., SEG Solar Inc., PT. SEG Solar Manufaktur Indonesia, and SEG Energy Singapore Pte. Ltd.
   • Patent Owner: Zhejiang Jinko Solar Co Ltd, Jinko Green Energy Shanghai Management Co Ltd (as the current assignees of US11824136B2).
   • Jurisdiction: Patent Trial and Appeal Board (PTAB).
   • Case Number: IPR2026-00230.
   • Filing Date: 2026-02-18.
   • Outcome or Current Status: Pending.

Proceedings overview

One Inter Partes Review (IPR) proceeding has been filed against US patent 11824136, and it is currently pending institution. This gives a defendant facing assertion of this patent today a relatively open defensive posture, as no claims have been invalidated or sustained by the PTAB yet. The sole IPR is in its early stages.

IPR2026-00230 — SEG Solar, Inc. et al. v. Zhejiang Jinko Solar Co Ltd

• Type: Inter Partes Review
• Filed: 2026-02-18
• Status: Pending. This means the PTAB has not yet decided whether to institute a trial on the challenged claims and grounds. The statutory deadline for an institution decision is typically six months from the petition filing date.
• Judge panel: Not yet publicly available for pre-institution phase.
• Petition grounds: Details regarding the specific claims challenged, prior art asserted, and statutory bases (§ 102 / § 103 / § 112) are not yet publicly detailed in the provided data or immediate search results for a pending IPR petition prior to institution.
• Institution decision: Not yet issued. The institution decision deadline is six months from the filing date, which would be approximately 2026-08-18.
• Final Written Decision: Not applicable as the proceeding is pending institution.
• Settlement / termination: Not applicable as the proceeding is pending institution.
• Appeal: Not applicable as the proceeding is pending institution.
• Defensive value: This proceeding indicates that at least one party (SEG Solar, Inc. et al.) believes there are valid grounds to challenge the patentability of claims in US11824136. As it is still pending institution, there is no final determination on any claims, and no estoppel has yet attached. A defendant should closely monitor the outcome of this IPR.

Strategic summary

Currently, all claims of US patent 11824136 remain untested by a Final Written Decision from the PTAB. There is one active Inter Partes Review, IPR2026-00230, which is in the pre-institution phase. Therefore, no claims are currently CANCELED or SUSTAINED, and all claims are UNTESTED.

Regarding the estoppel landscape, since IPR2026-00230 has not yet been instituted, no estoppel under § 315(e)(2) applies to any potential petitioners or their privies. If the PTAB institutes the IPR and subsequently issues a Final Written Decision, the petitioner (SEG Solar, Inc. et al.) and its privies would be estopped from raising any ground that was raised or reasonably could have been raised in the IPR concerning the claims subject to the FWD. For a defendant currently being asserted against, this means all prior-art grounds are still theoretically available for use in a new PTAB petition or district court litigation, as long as they are not privy to SEG Solar, Inc. et al.

There are no discernible pattern signals yet, as only one IPR has been filed. The petitioner is SEG Solar, Inc. et al. There's no indication of multiple IPRs by the same petitioner, aggressive PTAB appeals by the patent owner, or direct involvement of a defensive aggregator like Unified Patents as a petitioner, although Unified Patents is cited as a source of PTAB data regarding the case.

Recommended next steps

• Monitor IPR2026-00230 closely for the institution decision, which is expected by approximately 2026-08-18. This decision will be a critical milestone, indicating whether the PTAB believes there is a reasonable likelihood that at least one challenged claim is unpatentable.
• Access the public records for IPR2026-00230 via the USPTO PTAB E2E system to obtain the petition and stay informed about filings and deadlines.
• If the IPR is instituted, carefully review the PTAB's institution decision to understand the specific claims and grounds that will proceed to trial. This will provide valuable insight into the patent's potential vulnerabilities.
• If the IPR proceeds to a Final Written Decision, this decision will be critical for understanding the validity of the patent's claims and potential estoppel implications for future challenges.

Inventors

• Kun Yu (Employer: Zhejiang Jinko Solar Co Ltd / Jinko Green Energy Shanghai Management Co Ltd, based on original assignment)
• Changming Liu (Employer: Zhejiang Jinko Solar Co Ltd / Jinko Green Energy Shanghai Management Co Ltd, based on original assignment)
• Xinyu Zhang (Employer: Zhejiang Jinko Solar Co Ltd / Jinko Green Energy Shanghai Management Co Ltd, based on original assignment)

There are no unusual patterns indicating inventors departing the original assignee around the time of filing.

Original assignee

The entity named on the issued patent is Zhejiang Jinko Solar Co Ltd and Jinko Green Energy Shanghai Management Co Ltd. Zhejiang Jinko Solar Co Ltd is a major manufacturer of solar panels and associated photovoltaic products. Their primary line of business is the research, development, production, and sale of solar cells and photovoltaic modules. The company ships products embodying the claims of the patent, which relates to solar cell technology. Their current status is operating and active.

Assignment timeline

A search of the USPTO Patent Assignment Search database (https://assignmentcenter.uspto.gov/) for patent number US11824136 reveals no recorded assignments. This indicates that the patent ownership has not been formally transferred or recorded with the USPTO since its issuance. Therefore, the original assignees, Zhejiang Jinko Solar Co Ltd and Jinko Green Energy Shanghai Management Co Ltd, remain the recorded owners.

Timeline diagram

timeline
    title Ownership of US 11824136
    2021 : Priority date
    2022 : Application filed by Zhejiang Jinko Solar Co Ltd; Jinko Green Energy Shanghai Management Co Ltd
    2023 : Patent published and granted to Zhejiang Jinko Solar Co Ltd; Jinko Green Energy Shanghai Management Co Ltd
    2026 : Currently owned by original assignee

NPE / troll-pattern signals

1. Shell-entity transfer — not present. The patent remains with the original operating companies, Zhejiang Jinko Solar Co Ltd and Jinko Green Energy Shanghai Management Co Ltd.
2. Known asserter in the chain — not present. There are no recorded assignments to any known NPEs.
3. Repeat correspondent across the chain — not present. No assignment chain exists to observe recurrent correspondents.
4. Cascading transfers — not present. No transfers are recorded.
5. Pre-litigation transfer — unclear. While there are litigation cases associated with this patent family (IPR2026-00230 filed, US cases filed in Texas Southern District Court and California Northern District Court), there are no recorded assignments immediately preceding these filings. Therefore, it's unclear if any unrecorded transfers occurred to enable assertion.
6. Bankruptcy fire-sale — not present. The original assignees remain active and have not filed for bankruptcy.
7. Privateering — not present. There is no evidence of the patent being transferred to an NPE for assertion on behalf of an operating company.
8. Defensive aggregator (anti-NPE) — not present. The patent is not owned by a defensive aggregator.

Verdict

Insufficient data.
No assignment records are publicly available on the USPTO Assignment Center for US patent 11824136. While Google Patents indicates ongoing litigation associated with this patent family (e.g., IPR2026-00230, US cases in Texas Southern District Court and California Northern District Court), the absence of recorded assignments prevents analysis of ownership transfers, shell entities, or repeat correspondents. Without this information, it is not possible to confidently classify the patent's assertion pattern.

For verification, see the USPTO Patent Assignment Search for US11824136: https://assignmentcenter.uspto.gov/patents/11824136

I have thoroughly reviewed the provided "Full patent text" for US Patent 11824136B2. However, the document does not contain an explicit "References Cited" or "Prior Art Citations" section that lists other patent numbers. The background section of the patent discusses the general state of prior art in N-type TOPCon solar cells, but it does not cite specific patent or publication identifiers.

Without a list of specific patent citations within the provided authoritative text, I am unable to identify and analyze each individual patent citation as requested to determine its publication/filing date, brief description, and potential anticipation of claims under 35 U.S.C. § 102.

Obviousness Analysis under 35 U.S.C. § 103 for US Patent 11824136

This analysis assesses the obviousness of claims in US Patent 11824136 by combining existing prior art and common knowledge available to a Person Having Ordinary Skill in the Art (PHOSITA) before the priority date of 2021-08-04. Since the provided patent text does not include a "References Cited" section listing specific prior art documents, this analysis relies on the "BACKGROUND" section of US11824136, which describes the state of the art, as well as general knowledge in the field of solar cell manufacturing implied by the "Prior art keywords" and the patent's descriptions of known techniques.

A PHOSITA in the field of solar cell technology at the time of the invention would have possessed knowledge of N-type TOPCon solar cell structures and manufacturing processes, including surface texturing techniques and their benefits.

Combination 1: Existing TOPCon Solar Cell + Known Texturing Principles and Optimization

References/Knowledge:

1. Existing N-type TOPCon Solar Cell Structure: The "BACKGROUND" section of US11824136 explicitly describes "An existing TOPCon solar cell rear surface structure sequentially includes a semiconductor substrate, a tunnel oxide layer, a doped conductive layer and a passivation layer on the rear surface from the inside out." [cite: "An existing TOPCon solar cell rear surface structure sequentially includes a semiconductor substrate, a tunnel oxide layer, a doped conductive layer and a passivation layer on the rear surface from the inside out."] It also notes that the front surface of such cells typically has a texture, such as a "pyramid-shaped microstructure" [cite: "the second texture structure 11 may include a pyramid-shaped microstructure."], formed by various texturing processes like chemical etching, laser etching, or mechanical processes [cite: "The texturing process may be chemical etching, laser etching, a mechanical process, plasma etching, or the like."].
2. Known Problem with Flat Rear Surfaces: The patent's background further highlights a problem in existing TOPCon cells: "The polished rear surface of the silicon wafer has a flat structure, but the structure of the polished rear surface may directly affect the manufacturing of the tunnel oxide layer and the polycrystalline silicon layer, and then affect passivation performance and conversion efficiency of the solar cell." [cite: "The polished rear surface of the silicon wafer has a flat structure, but the structure of the polished rear surface may directly affect the manufacturing of the tunnel oxide layer and the polycrystalline silicon layer, and then affect passivation performance and conversion efficiency of the solar cell."]
3. General Benefits of Surface Texturing in Solar Cells: It is common knowledge in the solar cell industry that texturing surfaces can improve light trapping, reduce reflection, enhance contact between layers (e.g., metal electrodes and semiconductor), and reduce recombination, all leading to improved conversion efficiency. The patent itself mentions that the pyramid-shaped microstructure on the front surface "enables a metal paste to better fill the microstructure when the metal paste forms an electrode by screen printing, which obtains better electrode contact, can effectively reduce series resistance of the solar cell, and improves the fill factor." [cite: "The pyramid-shaped microstructure enables a metal paste to better fill the microstructure when the metal paste forms an electrode by screen printing, which obtains better electrode contact, can effectively reduce series resistance of the solar cell, and improves the fill factor."]
4. Routine Optimization: The process of optimizing surface structures and their dimensions (e.g., roughness, height, feature size) for improved material deposition, interface quality, and electrical contact is a routine task for a PHOSITA in semiconductor manufacturing.

Obviousness of Claim 1 (Solar cell structure):
Claim 1 describes a solar cell with a first texture structure on the rear surface, comprising "two or more first substructures at least partially stacked on one another," with a distance between top surfaces of adjacent substructures less than or equal to 2 μm, and a one-dimensional size of the outermost substructure's top surface less than or equal to 45 μm. It also specifies a first passivation layer on the front, a tunnel oxide layer on the first texture structure, a doped conductive layer, and a second passivation layer.

A PHOSITA, faced with the known problem that a "flat" polished rear surface negatively impacts the manufacturing of the tunnel oxide and polycrystalline silicon layers, and thus affects passivation performance and conversion efficiency [cite: "The polished rear surface of the silicon wafer has a flat structure, but the structure of the polished rear surface may directly affect the manufacturing of the tunnel oxide layer and the polycrystalline silicon layer, and then affect passivation performance and conversion efficiency of the solar cell."], would be motivated to modify this flat rear surface. Given the well-understood benefits of surface texturing on solar cell performance (e.g., for light trapping, reduced recombination, and improved electrode contact), it would be obvious to apply texturing principles to the rear surface to address these identified issues.

The specific "first texture structure" featuring "stacked substructures" and dimensional limitations (distance <= 2 μm, 1D size <= 45 μm) represents an optimization of surface topography. The patent itself states that this control "helps to improve the uniformity of the tunnel oxide layer formed on the first texture structure, ensure better performance of the tunnel oxide layer formed, further inhibit a high local phosphorus concentration caused by phosphorous diffusion, reduce contact resistivity, improve the open-circuit voltage of the solar cell, and improve the fill factor and photoelectric conversion efficiency." [cite: "the distance between the top surface of the outermost first substructure 121 a and the top surface of the first substructure 121 b adjacent thereto is controlled to be less than or equal to 2 μm, so that the roughness of the first texture structure is controlled within a desired range, which helps to improve the uniformity of the tunnel oxide layer formed on the first texture structure, ensure better performance of the tunnel oxide layer formed, further inhibit a high local phosphorus concentration caused by phosphorous diffusion, reduce contact resistivity, improve the open-circuit voltage of the solar cell, and improve the fill factor and photoelectric conversion efficiency."] Arriving at such specific dimensions and a "substantially “step” profile" [cite: "the first texture structure may present a substantially “step” profile, and the first substructure 121 may be regarded as a stair of the “step”"] through routine experimentation to optimize the deposition of the tunnel oxide layer and subsequent contact layers would have been within the capabilities of a PHOSITA.

Obviousness of Claim 14 (Method of manufacturing):
Claim 14 outlines a method for manufacturing a solar cell that includes texturing the front surface to form pyramid-shaped microstructures, forming a doped layer, polishing the rear surface with an alkali solution to form the specified first texture structure, and subsequently forming the tunnel oxide layer, doped conductive layer, and passivation layers.

A PHOSITA, manufacturing an existing TOPCon cell, would be aware of the negative impact of a flat polished rear surface on cell performance [cite: "The polished rear surface of the silicon wafer has a flat structure, but the structure of the polished rear surface may directly affect the manufacturing of the tunnel oxide layer and the polycrystalline silicon layer, and then affect passivation performance and conversion efficiency of the solar cell."]. The patent describes that prior art methods involved polishing the rear surface after removing borosilicate glass, resulting in a flat structure. [cite: "borosilicate glass on a rear surface of an N-type solar cell is removed by an oxidizing mixed acid solution.", "After the surface is cleaned and dried, the rear surface is polished with the aid of a trough or chain acid additive.", "The polished rear surface of the silicon wafer has a flat structure, but the structure of the polished rear surface may directly affect the manufacturing of the tunnel oxide layer and the polycrystalline silicon layer, and then affect passivation performance and conversion efficiency of the solar cell."]

Recognizing the need to improve this rear surface, a PHOSITA would be motivated to modify the existing polishing step to create a textured surface. The use of "alkali solution" for polishing or texturing silicon surfaces is a known technique in solar cell manufacturing, as evidenced by the patent's own description of forming front surface pyramid textures using "an alkaline solution such as a potassium hydroxide solution." [cite: "the texturing may be performed using an alkaline solution such as a potassium hydroxide solution. Since the corrosion of the NaOH solution is anisotropic, a pyramid-shaped microstructure can be manufactured."]

Therefore, it would be obvious to a PHOSITA to employ or adapt known alkali-based texturing/polishing techniques on the rear surface to generate a non-flat structure. The specific method steps described in dependent claims (e.g., cleaning with alkali solution of 5-15% mass fraction, spraying micro-liquid droplets for roughening, polishing with a liquid containing NaOH/KOH/additive at 70-80° C. for less than 260 seconds [cite: "the polishing a rear surface of the semiconductor substrate with an alkali solution includes: cleaning the rear surface of the semiconductor substrate with the alkali solution having a mass fraction of 5% to 15% to remove porous silicon; dropping, by spraying, micro-liquid droplets of the alkali solution to the rear surface of the semiconductor substrate for roughening treatment, and then performing pre-cleaning with a hydrofluoric acid having a mass fraction of 5% to 10%; polishing the rear surface of the semiconductor substrate with a polishing liquid at a polishing temperature ranging from 70° C. to 80° C. for a polishing time less than 260 seconds, wherein the polishing liquid includes NaOH having a mass fraction of 1% to 15%, KOH having a mass fraction of 1% to 15% and an additive having a mass fraction of 0.51% to 2.5%"]) for forming the "first texture structure" (with its specific dimensional ranges) would represent routine process optimization. A PHOSITA would routinely adjust polishing parameters (like time, temperature, and solution composition) to achieve a desired surface roughness and morphology suitable for subsequent thin-film deposition and improved electrical contact, as described by the patent itself. [cite: "a shape of the substructure in the first texture structure after polishing may be adjusted by controlling the polishing time and the polishing temperature, so that in the two or more first substructures at least partially stacked a distance between a top surface of the outermost first substructure and a top surface of the first substructure adjacent thereto is less than or equal to 2 μm in a direction away from the rear surface and perpendicular to the rear surface, so as to increase the roughness of the rear surface of the semiconductor substrate."]

Conclusion on Obviousness

The core inventive step claimed by US11824136—introducing a specific, non-pyramidal texture on the rear surface of a TOPCon solar cell with defined dimensions, and the method for producing it—appears to be an obvious modification of existing TOPCon solar cell technology. The motivation stems directly from a known problem in the prior art (the limitations of flat polished rear surfaces in TOPCon cells) [cite: "The polished rear surface of the silicon wafer has a flat structure, but the structure of the polished rear surface may directly affect the manufacturing of the tunnel oxide layer and the polycrystalline silicon layer, and then affect passivation performance and conversion efficiency of the solar cell."], combined with the well-established benefits of surface texturing in solar cell efficiency and contact optimization. The specific structural parameters and method details would be arrived at through routine experimentation and optimization by a PHOSITA aiming to improve the tunnel oxide layer uniformity, reduce contact resistivity, and enhance overall cell performance.