The world’s most efficient solar panel goes on sale later this year

Tandem PV shipped its “first production-quality panel” two weeks ago and expects revenue-generating sales later this year, according to CEO Scott Wharton.

To achieve bankability, Tandem will begin running paid pilot deployments with independent power producers (IPPs) later this year. Those paid deployments will begin the outdoor testing required for bankability, which Wharton said could be achieved after roughly 6 to 12 months of field data.

The company expects to reach high-volume, gigawatt-scale manufacturing in 2028, with possibly a 34% solar panel if its technology curve stays steady. The current demonstration format is roughly the size of a First Solar Series 4 module, while Tandem’s high-volume product is designed around standard 1-by-2-meter and 2-by-3-meter module formats of the solar industry. The demonstration module from June was 100 cm2.

When asked what needs to happen between now and commercial sales later this year, Wharton noted that it is overcoming the final engineering hurdles of translating processes from the R&D lab to panels that are 60 times larger, and he feels the team can clearly “see the finish line.”

Technology, efficiency, degradation

Degradation is traditionally the greatest issue with perovskites, but Tandem PV plans to offer a 30-year warranty with 1% or less module degradation per year. Wharton repeated claims that its most recent glass-glass solar modules have shown no measurable degradation after a year of outdoor testing. Wharton also believes the modules will feature a temperature coefficient half that of the best silicon modules available, nearing -0.15%/°C.

The key detail of Tandem PV’s product is its 4-terminal (4T) mechanically-stacked architecture. The perovskite layer is deposited onto the top solar panel glass, not directly onto the silicon cell below.

“To an 80-pound panel, we’re adding 5 grams of a liquid… it can fit in the size of a blueberry. So, the panel is more expensive, but the marginal cost of adding that 5 grams is actually lower than all the new power that we’re adding,” said Wharton.

Because the design is cell-agnostic, Tandem treats the underlying silicon cell as a pass-through cost. Wharton likened it to ordering at a restaurant: “It’s like selling a salad… You’ve got your base salad, and then you pick your protein.”

Tandem’s 30.4% record module was built on a Maxeon IBC solar cell, but it has tested positively with PERC, TOPCon, and HJT cells. This allows purchasers to specify their preferred silicon technology and source it domestically if they choose.

In its record 30.4% module, roughly 22% of the total efficiency came from the silicon cell, while about 8% came from the preovskite glass layer.

Tandem PV said in an interview with Roth Capital recently that it sees a clear path to adding 2% efficiency per year without any major scientific breakthroughs. This trajectory would put the module at 37% efficiency by 2030. The company also noted theoretical peak efficiencies of 45% for two layers of perovskite atop silicon, and 50% for three layers, crushing the 23% efficiency seen in mass production panels today.

Among the more astounding of the data points talked about, was the viability of reaching 37% without breakthroughs, purely through engineering. Wharton said:

“We see a whole bunch of things that we can continue to improve on the core perovskite, that we kind of have the idea of how to do it, but that we haven’t engineered them yet. And then there’s the opportunity to make the two of them work better together, because right now on the 30%, we’re getting about 8% on the silicon, but we think we can actually get more out of it over time. It’s moving out of the realm of science into more of its engineering and engineering effort.”

Maybe as a headline value, the company is targeting a 1,000-watt solar panel. A standard utility-scale module measuring 2,384 mm x 1,303 mm would need 32.3% efficiency to break the 1,000-watt barrier.

For context, the world’s most efficient terrestrial silicon solar panel currently for sale is probably around 25% efficiency and from LONGi or Aiko, while most commercial panels on the market today sit between 22% and 24%.

Economics and tariffs

“It’s an order of magnitude change,” the serial entrepreneur told pv magazine USA. He continued:

“If there’s a 30 to 32% panel out in the field, and you’re making a 23% panel, you’re kind of… you’re kind of in trouble.”

Li Zhenguo, founder and president of LONGi Green Energy, once noted that each 1% increase in cell efficiency translates into more than a 5% reduction in system costs. Wharton says one reason he likes selling to IPPs is that they intuitively understand 15 to 25% improvement in levelized cost of energy that Tandem PV’s greater efficiency brings.

Tandem PV management stated during the Roth interview, that it has signed letters of intent to sell approximately $1 billion in solar panels. At its noted “market-driven” average selling price of $0.40/W, this suggests roughly 2.5 GW in signed solar module capacity.

The company’s initial go-to-market strategy targets utility-scale IPPs, which make up roughly 80% of the U.S. market. However, Tandem is also in discussions with standard module manufacturers about unbundling the product to sell only its perovskite-coated top glass.

While recent Section 232 tariffs might force standard silicon module pricing upward, Wharton noted the tariffs have virtually no effect on its product, but it would increase the final price.

Tandem’s manufacturing facility is positioned to produce modules that qualify for domestic content and manufacturing tax credits. Because Tandem is cell-agnostic and treats the silicon base as a pass-through cost, customers can choose domestic silicon cells to pair with Tandem’s domestically produced perovskite glass. The Roth note points out this allows Tandem to stack wafer, cell, and module 45X credits (worth $0.14/W).

The capex required to manufacture the perovskite glass is estimated at $100 million per GW of capacity. When it was casually suggested during the pv magazine USA interview that Tandem would get a 50 GW order, Wharton responded seriously saying Tandem utilizes off-the-shelf equipment sourced from the semiconductor industry, and should be able to scale well towards a facility of that size.

Tandem PV has raised $100M across equity, debt, and grants to date, and is backed by names including Eclipse Ventures, Constellation Energy, Planetary Technologies, Trellis Climate, and 8090 Industries.

pv magazine USA inquired if anything humbled him during the development process, Wharton admitted that fundraising was incredibly challenging, a difficulty significantly compounded when the political tides shifted in Washington.

Wharton is confident in the continued progress of perovskite advancement.

“We just have to keep putting one foot in front of the other, do what you have to do, and then magic will happen,” Wharton finished.