Tunnel Oxide Passivated Contact (TOPCON) for Solar Cells
Overview · What matters in this field right now?
In short
Research
A one-nanometre oxide that conducts
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The cell rests on a contradiction resolved at atomic scale. A silicon oxide layer a few atoms thick should insulate. Here it carries one carrier type and blocks the other, and the whole advantage of the architecture follows from that.
The cell became a commodity, so the sale moved to the module
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Every TOPCon launch at India's REI Expo in late October was a module. Avaada showed a 745 W glass-to-glass panel at 23.98% module efficiency, with 132 half-cells and 18 busbars. Emmvee launched a quarter-cut design at 640 to 650 W, 25 to 30 W above a half-cut module of the same size. Saatvik and Solex both claimed 670 W and 24.8% with 264 quarter-cut cells. Shakti Pumps, a pump maker, entered with a 620 W 16-busbar panel and ALMM papers submitted. Sunbond wrapped its frame in glass-reinforced polymer so it will not pit in salt air.
Strategy
Six cell makers hold the invention, and the map is short
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Of the 1,203 patents published on this topic since 2021, 1,042 came from the Chinese office. WIPO accounts for 43, the United States 40, Japan 15, and Australia and Europe 12 each. India accounts for 9.
Research
The contact became the industry's standard cell, made two ways
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Most crystalline silicon cells now use this structure. The industry roadmap has it holding the lead through the mid-2030s, at roughly 70 to 80% of production in 2025 depending on the forecaster. Roadmap mass-production efficiency is 25.6% for 2026, rising to 26.4% by 2036. Chinese leaders report 26.1 to 26.5% at cell level and yields near 97%, against 25.1 to 25.3% for cells measured after module assembly.
Market
A cell line is sold as a machine, a recipe and a patent licence in one package
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New capacity is bought as a bundle, and which bundle depends on who is buying.
Strategy
The most prolific recent filer is working on the oxide interface
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In patents published from June 2025 onward, Aiko's legal names account for 64, Trina 43, Tongwei 27, Dmegc 21, Das Solar 19, Jietai 17 and Jinko 17.
Research
The invention concentrates in the stack, and the stack became a process window
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Of the 1,203 patents published on this topic, 855 sit in passivation and deposition, more than every other area together. That concentration is the clearest thing the patent record says: the field is deepening in one step.
Market
India's protected price is what makes those orders signable
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The buying wave answers a rule, not demand. From 1 June 2026 India required domestic cells for government-backed projects, at a point when approved cell capacity was roughly 31 GW against 193 GW of module capacity. Approved cell capacity passed 35,467 MW by August, with 3,709 MW added in one month.