Naysayers about the long-term impact of perovskite-tandem solar technology “don’t understand economics”, says Scott Wharton.
The CEO of Tandem PV, a Silicon Valley startup that now claims to be on the verge of shipping full-size tandem modules to US clients for paid trials, oozes Californian optimism when we speak on a video call. He says that the perovskite-tandem solar technology his company and others are working on, elusive and long in the making as it has been, will “dominate the market” within six years. And he thinks it’s Silicon Valley culture that has made that possible.
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The last 18 months have been busy for Tandem PV. In March 2025 it raised US$50 million from venture capital firm Eclipse to fund a commercial-scale tandem module production line; in April this year, it began operations at that demonstration facility in the Silicon Valley enclave of Fremont, California; and in August it bagged a US$7.7 million grant from the Department of Energy (DOE) that the company said would speed up the rollout of its tandem modules, which it claims have a 29.7% conversion efficiency.
And in June, former US energy secretary Jennifer Granholm joined the company’s board of directors, bringing real industry clout and respect.
All of those developments are “votes of confidence from people from the outside in our ability to be successful,” Wharton says. “Jennifer Granholm is not on many boards at all, so it’s a real honour to have her participating with us. Same with the DOE—I think we were the only company in the solar space that won a grant for that particular programme.”
Wharton—a serial startup businessman rather than a solar specialist—spells out a formula for success that wouldn’t be out of place in a sales pitch: “You need three things to commercialise perovskites—efficiency, durability and manufacturability.”
Tandem PV has shown efficiency, he says, with its 29.7% demonstration modules, and he claims that the company has achieved less than 1% degradation per year on its products. Those claims have apparently been verified by bodies including the National Renewable Energy Laboratory (now the National Laboratory of the Rockies) and Renewable Energy Testing Centre (RETC), though that certification has been absent from the company’s public announcements.
“I think there have been a bunch of announcements in the industry, but they don’t really mean anything unless you have the durability to be commercially viable,” he says.
“And then the third thing is, can you take all that and not just make it on a small form factor, but can you do it on something bigger? And I think that’s where we’ve gone recently. In our demo facility, we’re now showing that we’re making large things that are about as good as what we did in R&D.”
How has Tandem PV seemingly overcome the degradation issue that has plagued everyone trying to commercialise perovskite products over the years?
“It’s a hard question to answer,” says Wharton, “It’s kind of like saying why is Nvidia the best at chips, or why does Anthropic have a great model?”
Tandem PV is not the only company that claims to have begun commercial tandem module production. UK-based Oxford PV has reportedly sold its first commercial-scale tandem modules for pilot testing, alongside licensing its patent portfolio to major commercial solar manufacturers, and other players have made claims about approaching industrial production.
Wharton says that his company’s team is a big part of its success, featuring “about 20 PhDs” and its chief technology officer, Colin Bailie, who was involved in developing what was reportedly the world’s first silicon-perovskite tandem cell while at Stanford University. That team built a platform of solutions over the years, Wharton says.
“I’d say a couple of years ago we basically got the perovskite stable enough that we could start seeing other failure conditions,” he explains. “One thing we found: in order to make progress in durability, it’s kind of like peeling away layers of an onion—unless you get your core perovskite layer stable, you never see all the other failure conditions.
“Once we solved that problem, then we could keep pushing the envelope farther to go from hundreds of hours to 1,000 hours to many thousands of hours to being more than a year outside without any degradation.”
Before the end of the year, Tandem PV expects to start paid trials with “more than a dozen of the big players” in the US independent power producer (IPP) market. The goal is not to make money, but to get a significant amount of modules in the field in order to prove that the product is bankable.
Then, Wharton said the company is planning to scale up a “gigafactory” by 2028.
Tandem PV is squarely targeting the utility-scale sector with its tandem modules. That may be a surprise to some, as perovskites are fairly often thought of as a niche technology, suitable for small-scale applications in space, small rooftops or other specialist deployments.
Some have gone further in their scepticism, arguing that time and money spent on perovskites is effectively wasted, when crystalline silicon PV is already abundant, understood, stable and cheap.
But Wharton is adamant against both of those positions. Of the true sceptics, he says “they’re right” that silicon PV is an established technology, but “they don’t understand how economics works.”
“If you have a 22% [efficiency] panel and it works, great. No arguments there.” But the value of a higher efficiency panel, he says, is that “the more efficiency you have, you need less labour, less land, less balance of system, and that lowers the overall cost. The whole reason the world went from PERC to TOPCon—and you notice the whole industry moved—was to get a 2% efficiency [boost]. Tandems are 7-12%.”
And he continues: “Unlike the shift from PERC to TOPCon, this is not a replacement. Because they’re tandems, you could leverage all of the [existing] TOPCon infrastructure or other technologies. Once you have products out there that are at 30% that are cheaper for the customers, no one will buy a 22% panel anymore. If you’re not at 30%, you’re out of business—it’s a fundamental economic shift.”
Wharton paints that shift as the “tip of the spear” for solving climate change. “I know we’re not supposed to talk about that anymore,” he says, referencing the broad industry turn away from climate-related messaging towards energy security and economic benefits, particularly in the US. “But that’s why I picked this particular thing [as his next startup project], because I saw it as one of the most meaningful impacts I could have—that the team could have—to solve climate change.”
The anti-renewables rhetoric coming from the Trump administration seems not to faze Wharton too much, and a few minutes later in our discussion, he emphasises the importance of “better economics and physics”. In true Silicon Valley fashion, the technology emerges as his guiding light.
“It doesn’t matter what your ideology is. I think sometimes people pick things because they go, oh, it’s good for the world—and it is. But I picked it because it had better economics and physics; because you can ask people to do something that is good for the environment, but if it’s not cheaper, most people will not do it. I’m counting on people doing this because they’re greedy, and then solving climate change is a nice little after-benefit.”
In the corner of Wharton’s screen, covering a portion of the white-tiled floor behind him, is a rug depicting the California state flag. The state has been a historic centre for solar technology and research, alongside the wealth of other technologies it continues to let loose on the world. And recently, movements in perovskite tech seem to be coming out of the US, and particularly the West Coast. As well as Tandem PV, the perovskite glass company Caelux is down the coast outside Los Angeles, and technology company Swift Solar is also in the Bay Area.
“I think it’s a culture of leapfrogging,” Wharton says. He thinks there are two ways people view the solar industry: one, that China is dominating manufacturing, so US companies should try to replicate their success at home. The second, that China is dominating manufacturing, so US companies should jump ahead to the next frontier.
“Typically, it’s very hard once you’ve lost an industry and there’s a group of people that are ahead and dominating. It’s very hard to win that back. I think the culture in the US is more like, well, we lost that—let’s leapfrog and go to the next level, kind of like the US did on mobile phones or video conferencing or AI. Go to the next thing.
“We would not take anything away from what the Chinese have done. But if you look at why they were so good at silicon, it was basically 25 years of very small manufacturing tweaks. There’s not much difference inherently between PERC and TOPCon, they’re just small process changes.
“I think that’s where Silicon Valley has an edge over people who are manufacturing-oriented. We know how to innovate and go faster and leapfrog in a new area.”
It’s a softer variation on the “move fast and break things” cliché that arose from the early days of Facebook. Wharton and Tandem PV seem to be the tech bros of the current solar industry, with a fundamental faith in technology and who keen to move as quickly as possible to “disrupt” the industry.
Wharton assumes the ascendence of perovskite tandem products, and speaks about it in Silicon Valley terms. “I think the future, from that point of view, is fairly clear. Now it becomes more of an execution risk, and what I like about it is we’re moving out of the science realm more into the process engineering realm.
“I think we have a pretty well-trodden path to becoming a multi-billion-dollar company and a leader in this space by scaling up. We just have the small matter of doing the work, but that’s the fun part.”
Scott Wharton will be speaking at the 2026 edition of PV CellTech conference on 13-14 October in San Francisco, where innovations in solar PV manufacturing will be a mainstay of the agenda. For the full agenda and information on tickets, click here.

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