Heterojunction Solar Cell Patents: Top Companies & Trends 2026
- China dominates the filing base. 801 of the tracked receiving-office filings are Chinese, versus 127 in the US and 76 via WIPO — the claim environment for TCO and low-temperature process work is now set primarily in China.
- Filing activity has already peaked and is easing off. Filings ran 71 in 2017, peaked at 145 in 2021, and sat at 106 by 2022's midpoint — this is a technology past its filing crest, not one still accelerating.
- Co-filing clusters point to integrated manufacturing groups. The strongest co-assignee pairs link a cell maker to its equipment or subsidiary arm (11 and 9 shared families), showing HJT IP is being built inside vertically integrated production chains, not by isolated R&D units.
Filing growth compares 2021 (145 records) with 2024 (75) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field. Top-5 share is the combined record count of the five largest assignees divided by all 1,213 records in scope (CR5), not by the ranked leaders only.
What the patent record shows about heterojunction solar cells
Heterojunction solar cell (HJT) technology combines a crystalline silicon wafer with thin amorphous silicon passivation layers, and the patent record tracked here follows exactly that seam: filings tagged against amorphous silicon passivation, transparent conductive oxide (TCO), low-temperature process steps, surface cleaning and efficiency claims, all sitting under IPC classes H01L31, H01L21 and C23C16. Across 1,213 patent families spanning 2015 to mid-2026, the claim activity concentrates overwhelmingly in H01L (semiconductor devices) with a secondary, much smaller cluster in C23C (coating and surface deposition) — the two process families a TCO or passivation layer actually has to pass through.
Filing has already crested: activity built from 71 families in 2017 to a peak of 145 in 2021, then eased toward 106 by 2022, with the most recent years understated by the usual 18-month publication lag. Read together with the receiving-office split — China far ahead of the US, WIPO and Europe — the picture is a maturing, China-centred claim base where the open questions are less about whether HJT works and more about which specific layer stack, deposition sequence or subsidiary is holding the strongest position.
Filing trend and technology composition
Two views of the same 1,213-family dataset: how filing volume has moved year over year, and how those families split across the IPC subclasses that define the technology's process boundaries.
Filings rose to a 2021 peak, then declined
Annual filings climbed from 71 in 2017 to a peak of 145 in 2021, then fell to 106 by 2022 — the midpoint of the tracked range. The 2026 figure reads as zero only because publication has not caught up; treat the last 18 months of any such trend as undercounted, not as a genuine drop-off.
H01L dominates; C23C is the only meaningful second cluster
H01L (semiconductor devices) covers 1,197 of the 1,213 families — almost the entire dataset — with C23C (coating and surface deposition) a distant second at 108. Smaller counts in H10P, H10K, B82Y, H10F, H01B and C30B mark adjacent branches — organic semiconductor crossover, nanotechnology applications, crystal growth — where filing density is thin enough to be worth a closer look.
Shares are the percentage of the 1,213 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Heterojunction Solar Cell Technology with Eureka
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Try EurekaThe prior art shaping freedom to operate
Transparent conductive oxide film and heterojunction solar cell
The application covers a transparent conductive oxide film built from a seed layer, a conductive layer and a protection layer: an indium tin oxide or gallium/aluminum co-doped zinc oxide seed, a gallium/aluminum co-doped zinc oxide conductive layer, and an indium tin oxide protection layer, with the ITO thinner than the doped zinc oxide layer. The stated aim is to hold cell efficiency while reducing battery attenuation.Filed by Tongwei Solar (Chengdu), published 2024-05-16 — illustrates how current claims are narrowing to specific layer-thickness relationships within the TCO stack rather than the stack's existence.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US5141564A | Mixed ternary heterojunction solar cell | 218 |
| 2 | US5342453A | Heterojunction solar cell | 194 |
| 3 | US20070169808A1 | Solar cell | 192 |
| 4 | US20100015756A1 | Hybrid heterojunction solar cell fabrication using a doping layer mask | 141 |
| 5 | US5316593A | Heterojunction solar cell with passivated emitter surface | 128 |
| 6 | US5474939A | Method of making thin film heterojunction solar cell | 126 |
| 7 | US20100300507A1 | High efficiency low cost crystalline-si thin film solar module | 99 |
| 8 | US20090293948A1 | Method of manufacturing an amorphous/crystalline silicon heterojunction solar cell | 97 |
| 9 | CN1588649A | 硅薄膜异质结太阳电池的制备方法 | 74 |
| 10 | US20120031478A1 | Heterojunction Solar Cell | 71 |
Citation counts reflect influence within this searched corpus and skew toward older filings; they are a signal of foundational status, not of current commercial relevance.
Patent titles are shown in the language they were filed in, not translated, so that each record stays verifiable against the original filing — a translated title will not match in Eureka or in any national register. Each row carries its publication number; clicking a row searches Eureka by that number.
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Browse MCP servers →What the numbers mean for a filing decision
Three patterns in the dataset matter more than the raw counts: where claim density sits, how concentrated ownership is, and where the filing curve is heading.
Nearly the entire corpus sits in one IPC subclass
H01L (semiconductor devices) accounts for almost all tracked families, with C23C (coating and deposition) a distant second at 108. A new entrant filing squarely in H01L is filing into the most contested space in the field; the deposition-process angle under C23C is comparatively less crowded.
The filing curve has already turned down
Activity rose from 71 families in 2017 to a 2021 peak of 145, then declined to 106 the following year. Combined with recent-year assignee momentum showing several major filers at zero in the latest tracked year, this reads as a technology consolidating rather than one still in a land-grab phase.
China is the primary venue for HJT claims
China accounts for the large majority of receiving-office filings tracked, well ahead of the United States, WIPO/PCT and Europe combined. Freedom-to-operate analysis that ignores Chinese filings is analysing a minority of the relevant claim base.
Co-filing clusters trace vertically integrated groups
The strongest co-assignee pairs link a cell producer to an affiliated equipment or subsidiary entity, with the top pair sharing 11 families. This points to IP being generated inside integrated manufacturing groups rather than through arm's-length licensing or standalone R&D shops.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to heterojunction solar cell technology, with the prior art for and against each one.
Who is filing, and where the field is still open
Assignee activity clusters around a small number of integrated Chinese solar manufacturers and their subsidiaries, with a long tail of single- or few-filing entrants. Recent-year momentum has cooled across most of the visible leaders at once, which is more consistent with a maturing claim base than with any one firm pulling ahead.
Several top assignees show no latest-year filings
Major names in the dataset — including large integrated solar manufacturers — register zero filings in the most recent tracked year. Given the 18-month publication lag, this understates true activity, but the pattern across so many leaders at once suggests filing has genuinely slowed, not just been delayed in publication.
Ownership is structured around manufacturing groups
Ten co-assignee pairs appear in the dataset, the strongest linking a cell producer with its equipment-side or regional subsidiary. This is a sign that HJT patent strategy is executed jointly across a group's manufacturing and process-equipment arms rather than by a single central R&D unit.
The competitive centre of gravity is Chinese
With 801 receiving-office filings in China against 127 in the US and 76 via WIPO, the assignees setting the pace on TCO layer design and low-temperature process claims are predominantly Chinese solar manufacturers and their subsidiaries.
| Assignee | Recent year | YoY |
|---|---|---|
| Trina Solar Co., Ltd. | 0 | — |
| Fujian Jinshi Energy Co., Ltd. | 0 | — |
| Jiaxing CSI Technology Research Institute Co., Ltd. | 0 | — |
| International Business Machines Corporation (IBM) | 0 | — |
| Juntai Innovation (Beijing) Technology Co., Ltd. | 0 | — |
| Tongwei Solar (Chengdu) Co., Ltd. | 0 | — |
| Suzhou Maxwell Vision Technology Co., Ltd. | 0 | -100% |
| Suzhou Maxwell Technologies Co., Ltd. | 0 | -100% |
Where to take this analysis
The filing trend and assignee map above answer who has claimed what. Turning that into a filing or freedom-to-operate decision means going deeper on the specific claims and the entities holding them.
Map claims against a specific layer stack
Run the TCO seed/conductive/protection-layer thickness relationships in the featured filing against your own process design to see which combinations are already claimed.
Explore in Eureka →Track the integrated manufacturing groups
The co-assignee clusters suggest IP strategy is coordinated across production and equipment subsidiaries — worth watching for future joint filings from the same groups.
Explore in Eureka →Watch the under-claimed IPC branches
C30B, H01B and B82Y carry far fewer filings than H01L; a narrowly drafted claim in one of these adjacent branches faces less prior art to design around.
Explore in Eureka →Common questions on heterojunction solar cell patents
The dataset shows filing concentrated among a small number of integrated Chinese solar manufacturers and their subsidiaries, rather than a single dominant global holder. Co-assignee patterns — such as a cell producer filing jointly with its equipment or regional subsidiary arm — suggest ownership is structured around manufacturing groups rather than centralized R&D units. Anyone doing freedom-to-operate work should check both the parent and subsidiary names, since families are often split across them.
This dataset is scoped specifically to claims touching amorphous silicon passivation, transparent conductive oxide layers, low-temperature processing, surface cleaning and efficiency, filed under IPC classes covering semiconductor devices and surface coating (H01L, C23C). That combination is what distinguishes heterojunction cells from standard homojunction silicon cells: the amorphous silicon passivation layer and the low-temperature TCO deposition step are the two process elements that generate almost all of the claim activity here. Most of the corpus sits in H01L, with coating-related claims a smaller but distinct second cluster.
No — filing activity peaked at 145 families in 2021 and had declined to 106 by the following year, with several major assignees showing zero filings in the most recent tracked year. Because publication typically lags filing by around 18 months, the very latest years in any such trend will always look artificially low, so some caution is warranted before calling the technology fully mature. But the multi-year decline from a clear peak, visible across many leading filers simultaneously, points to a claim base that is consolidating rather than still expanding.
The IPC composition shows H01L (semiconductor devices) holding nearly the entire dataset, meaning that space is heavily claimed. The comparatively thin filing counts in adjacent classes — crystal growth (C30B), conductors and insulators (H01B), nanotechnology applications (B82Y), and organic semiconductor crossover (H10K) — mark areas with far less prior art to design around. A first claim drafted narrowly around one of those adjacent process steps, rather than the core TCO or passivation layer stack itself, is more likely to clear a novelty search.
The filing, from Tongwei Solar (Chengdu) and published in 2024, claims a transparent conductive oxide film built from a specific seed layer, conductive layer and protection layer arrangement, with an explicit constraint that the indium tin oxide layer be thinner than the doped zinc oxide conductive layer. It does not block TCO films generally — it blocks that particular thickness relationship and layer ordering. A design that inverts the thickness relationship, uses a different seed material, or omits the protection layer would sit outside this specific claim, though it would still need checking against the wider TCO claim set in the H01L/C23C cluster.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.