Walk past any new subdivision or commercial rooftop in America and you will likely see them: dark blue rectangles arranged in rows, soaking up sunlight and quietly converting it to electricity. Most people assume a solar panel is essentially a sheet of glass over silicon. The real story is considerably more intricate.
Inside nearly every panel installed today is a specific engineered layer just nanometers thick that most homeowners, and many installers, have never heard of. That layer is now the subject of a federal investigation that could shake up every panel price in the country.
How a panel actually starts: sand, heat and extraordinary purity
The journey begins not on a rooftop but in a furnace.
The manufacturing process for a crystalline silicon solar module starts with mined quartz being purified from silicon dioxide into solar-grade silicon, including heating the quartz in an electric arc furnace.
The solar-grade silicon is crushed into chunks, melted down, and cylindrical monocrystalline ingots are then pulled out of a vat of molten silicon.
After the ingot is formed, it is sliced into ultra-thin silicon wafers, 150 to 200 microns thick, with precision diamond wire saws.
The silicon sawdust created in that cutting process is called kerf. Almost none of that costly purified silicon is recovered.
From wafer to cell: the step that actually makes electricity
The first step in turning a wafer into a cell is chemical texturing of the wafer surface, which removes saw damage and increases how much light gets into the wafer when exposed to sunlight.
Then comes doping. Doping is the process of adding impurities into the crystalline silicon wafer to make it electrically conductive, using materials like boron for p-type and phosphorous for n-type silicon.
That p-n junction is the engine of the whole device. Photons knock electrons loose; the junction sends them in one direction, creating usable current. But for decades, the surface of the cell bled energy away as fast as the junction could generate it.
Defects at the silicon surface act like drains. Engineers spent years trying to seal them.
The efficiency arms race that quietly rewrote the factory floor
The older mainstream technology, known as PERC, added a reflective rear layer to capture more light. It was a significant step. But a newer design pushed further.
TOPCon, tunnel oxide passivated contact, places an ultrathin oxide layer just a few nanometers thick between the silicon and a doped polysilicon film. Electrons tunnel through the oxide quantum mechanically, while the layer itself blocks the energy-wasting recombination that PERC could not fully stop.
N-type TOPCon offers clear advantages over p-type PERC, including higher conversion efficiency, a better temperature coefficient and superior resistance to degradation.
The gains are real enough that the entire industry pivoted fast. The rise of TOPCon technology has been impressive: as of the start of 2026, it accounts for almost 85% of global production, while mono PERC has declined to less than 5%, according to market analysts CRU.
The patent buried inside 85% of the world’s solar panels
Here is the part the industry did not see coming. A thin-film manufacturer that does not even make silicon panels holds key patents on the TOPCon process, and it is now enforcing them at the federal level.
First Solar, a cadmium-telluride thin-film solar panel manufacturer, holds a silicon solar panel patent involving tunnel oxide passivated contact (TOPCon) technology, U.S. Patent No. 9,130,074, which forms the basis of its ITC complaint.
First Solar obtained the TOPCon patents through its 2013 acquisition of TetraSun, Inc. Prior to its acquisition, the California-based startup had developed proprietary cell architecture and manufacturing processes for large-format crystalline silicon wafers.
On February 24, 2026, First Solar filed a complaint with the U.S. International Trade Commission alleging violations of Section 337 of the Tariff Act of 1930 in the importation into the United States of certain TOPCon solar cells, modules, panels, components thereof, and products containing same, claiming they infringe the asserted patent.
In an official notice, the ITC named a total of 47 affiliated entities from across the globe as respondents, falling into 10 core corporate groups including Axitec, Canadian Solar, JA Solar, JinkoSolar, Mundra/Adani, Philadelphia Solar, Hanwha Q CELLS, Runergy, Trina Solar/T1 Energy and VSUN/Toyo.
The complainant requests that the USITC issue a general exclusion order, or in the alternative a limited exclusion order, and cease and desist orders. A general exclusion order would bar all infringing TOPCon imports, regardless of manufacturer. That would cover the dominant technology in nearly every panel on the market.
The patent challenge is already bending the domestic manufacturing landscape. As covered in our look at U.S. solar module manufacturing in Q1 2026, new capacity additions have stalled as policy and IP uncertainty compound each other.
What a federal exclusion order would mean for panel prices at home
The ITC case is still at the procedural stage and has not yet reached a final infringement ruling. But the investigation alone is already reshaping factory decisions inside the United States.
First Solar’s TOPCon patent enforcement actions have pushed domestic crystalline silicon cell manufacturers toward PERC and heterojunction process alternatives, with industry analysts projecting that PERC and HJT could account for a growing share of U.S. c-Si cell output through 2026.
First Solar is licensing its TOPCon technology and has already established a relationship with Talon PV, a cell manufacturing startup in Texas, giving First Solar a domestic industry basis to request the federal review of TOPCon imports.
If the ITC ultimately issues an exclusion order, importers would need a license or a redesigned cell to ship into the United States. Either path adds cost, and that cost flows downstream to the American households already paying significantly more for electricity than they did just a few years ago.
The nanometer-thin tunnel of oxide that makes a solar cell more efficient is, for now, also the thinnest line between the current panel market and a very different one.
