Perovskite Solar Is Having Another Moment

Over a decade ago, when the global price of silicon-based photovoltaic modules was roughly five times what it is today, the solar industry and media were already hyping up the next big thing: perovskites, a class of materials defined by their specific cube-like crystal structure. The technology promised to boost photovoltaic efficiency while driving down costs, and the industry was atwitter.

“All the cool solar-cell scientists are working on perovskites photovoltaics,” IEEE Spectrum proclaimed in a 2014 article. In the same piece, Oxford Photovoltaics predicted that it would have commercially available cells within four years. The Wall Street Journal profiled the tech that same year, and in 2015, The Guardian declared that perovskites could be “game changing.” The excitement centered around the potential for higher output at lower costs: Perovskite cells were seeing rapid efficiency gains, could be made from cheap materials, and were remarkably thin and lightweight. When the question of durability came up, it was often as an afterthought. But that has turned out to be the technology’s biggest obstacle.

“What the industry came to understand very quickly is that, yes, you could see higher efficiency, but that material is going to degrade pretty quickly,” Laureen Sanderson, chief communication officer at the perovskite startup Cubic PV, told me. “A lot of the efficiency records that you were seeing were records that were achieved on very small scale devices in a laboratory environment, potentially measured in the dark.” Not ideal for a technology designed to soak up the sun on a large scale.

It’s true that perovskite cells tend to break down rapidly on contact with moisture, heat, and light, a problem scientists have been slowly chipping away at in the lab. That fragility largely arises because perovskites are made of electrically charged ions held together mostly by the attraction between positive and negative charges, much like magnets snapping together. That’s an intrinsically looser structure than the covalent bonds in silicon, which fuse the atoms together via shared electrons. As a result, the ions in perovskites migrate when exposed to the elements, accumulating in places where they react with surrounding materials to form unwanted byproducts that gradually break down the cell’s structure.

But while durability has been its fatal flaw, efficiency is perovskite’s superpower. Silicon’s efficiency tops out at 29.4%, a fundamental physics limitation that no amount of engineering can overcome. But because perovskites can be tuned to absorb different wavelengths of light beyond what silicon can capture, stacking a thin perovskite cell atop a conventional silicon cell lets the combined device make use of more sunlight than either material could alone. In July, one of these silicon-perovskite tandem cells — the industry’s dominant architecture — set a new 35.5% efficiency record.

So while this new tech still doesn’t match the stability of conventional panels, it’s getting much better. Tandem cells hold up increasingly well when exposed to heat, light, and moisture in the lab, and early outdoor trials are starting to produce promising real-world performance data. With headlines about perovskites starting to roll in once more, scientists say there’s good reason to believe that, this time around, the hype might actually be justified.

“Over the better part of a decade, there’s been lots of, for want of a better word, device engineering to engineer the material to just be much more stable,” Sam Stranks, an energy materials professor at the University of Cambridge and co-founder of perovskite startup Swift Solar, told me. That includes swapping out an unstable chemical building block in perovskites called methylammonium with a more stable one called formamidinium, improving the connection point that binds the perovskite layer to the electrode layer, and improving the packaging of perovskite cells to seal them off from air and moisture.

“There’s still work to be done to really get it to the point where you could put it up on a rooftop for 25 years and you know it will last. But the trajectory is very promising,” Stranks said.

Scientists have managed to extend perovskite durability from mere hours to the point where cells and modules are now passing industry-standard tests that suggest they could survive outdoors for five to 10 years. That’s still a ways away from the standard 25-year warranties for silicon solar panels, which typically guarantee that a module will retain 85% to 90% of its original output by year 25. And because these latest perovskites simply haven’t been around that long, scientists have yet to test these more ambitious durability claims in the real world.

Industry experts say there’s no reason continued incremental improvements can’t get perovskites to that 25-year standard relatively soon, however. “If you look at silicon, it’s been 70 years of trial and error,” Scott Wharton, CEO of perovskite startup Tandem PV, told me. “Seventy years of constant tweaking and improvement, whereas perovskites have only had about 12.”

Wharton said that Tandem’s testing indicates its panels will degrade at a rate of less than 1% per year. Furthermore, he predicts perovskites will become the dominant solar technology by 2033, a more ambitious timeline than others in the industry typically project. But as he sees it, seven years is roughly enough time to build and deploy two generations of perovskite factories — the kind of iterative ramp-up he says new technologies typically need to achieve market dominance.

The economics just make sense, he told me. Because perovskites are more efficient, they will produce more power per unit — which means less land, hardware, wiring, and labor needed to achieve the same total energy output, driving down costs at every step of the process. Why wouldn’t everyone jump onboard immediately? “All of our customers have said that once we’ve proven it out, they’re going to move,” Wharton told me. “They’re going to move 100% to tandems because of the power of the efficiency gains.”

Others are somewhat more measured regarding how long this may take. Stranks predicted it would be about five years before perovskites with multi-decade warranties even begin hitting the market, while Sanderson estimated they’ll gain real commercial traction by 2029, with perovskites making up a “significant portion of the market” throughout the 2030s.

While the date of that tipping point remains up for debate, the industry appears to have largely settled the question of materials. At least for now, the preferred configuration is to pair a lead-based perovskite cell with silicon rather than build an all-perovskite cell, which would likely face even greater durability challenges. That’s because such a cell would also need a tin-based perovskite layer to capture lower-energy light like silicon does, but tin degrades even faster than lead. In other words, it’s easier to keep silicon — a proven, durable material — in the mix by building so-called “tandem cells” for the foreseeable future.

But there’s still plenty that remains unknown. Every startup’s exact chemistry is proprietary, and there’s no clearly dominant formula yet. There’s also no industry consensus on the architecture best poised to address perovskite’s stability challenge, either, with leading players typically taking one of two different approaches.

Stranks’ Swift Solar team is pursuing what’s known as a “two-terminal” tandem architecture, in which a manufacturer builds the perovskite layer directly on top of the silicon layer, with the two cells functioning as a single unit. That’s opposed to a “four-terminal” design, where companies build two independent perovskite and silicon cells and then mechanically stack them on top of each other rather than fusing them together.

Two-terminal is the more widely studied approach, pursued by other industry leaders such as Oxford PV — the same company that once predicted commercialization by 2018 — along with Chinese solar giants LONGi and JinkoSolar. Proponents argue that using fewer material layers means less light lost, which translates into greater efficiency and lower costs. In a blog post last year, Swift Solar’s team also argued that the four-terminal designs rely on laser cutting, which it says can create more entry points for degradation.

Two-terminal isn’t just the leading theoretical contender, it’s the first architecture to officially make it to market. Oxford PV’s finally executed its long-delayed commercial launch in 2024, shipping its modules to an undisclosed U.S. customer for use in a utility-scale solar project. It was the world’s first commercial sale of perovskite panels, which Oxford claimed could produce up to 20% more energy than standard silicon modules.

But newer market entrants such as Cubic PV and Tandem PV are bullish on the four-terminal approach. For one, while two-terminal designs use fewer materials, they are more difficult to manufacture. Building a perovskite layer directly onto silicon’s rough surface is more technically difficult than coating it onto smooth glass, as Cubic and Tandem do. And because four-terminal companies manufacture the perovskite and silicon cells separately, they can swap in whatever silicon cell is cheapest or most efficient at any given moment, rather than being locked into a single supplier’s tech.

That flexibility could prove important as the market moves beyond early adopters. For now, Stranks said, customers buying tandem modules are probably doing so for strategic testing purposes — placing small, one-off orders to trial the tech themselves. An installer today can’t simply go buy perovskites on the open market by consulting a public pricing list or product catalogue the way they can with silicon panels. “But it’s not too far away before that would be the case,” he explained.

For its part, Swift is moving … swiftly, acquiring the manufacturing assets and IP of the bankrupt Swiss silicon cell maker Meyer Burger this spring. The company plans to use those assets first to build a U.S.-based gigawatt-scale silicon cell and module factory to meet demand for domestically manufactured solar cells, eventually adding silicon-perovskite tandem module production to that same facility.

Tandem PV is also pushing ahead with plans to begin selling to customers by the end of this year “in a volume that would be big enough to hit bankability goals,” Wharton told me. It also plans to bring a gigawatt-scale factory online by 2028. The company is targeting the independent power producers who build, own, and operate most utility-scale solar projects today. And like Oxford, Swift, and Cubic, Tandem is focused primarily on the utility-scale solar market — by far the biggest opportunity for perovskite technology.

Cubic scrapped plans in 2024 to build a facility producing silicon wafers — the raw material used to make solar cells — amid collapsing wafer prices globally and surging construction costs domestically. While Sanderson says the company remains interested in building its own factory, it has no timeline for doing so. But in the meantime, it’s also interested in licensing its IP to other perovskite companies.

The outlook for domestic wafer production has improved in recent years, though, after the Biden administration provided stronger financial incentives for producing wafers in the U.S. The Trump administration has kept these in place, though it’s made domestic content requirements stricter and more complex overall.

There’s also another new policy variable in the mix: Section 232 tariffs on cheap silicon wafers from China. Going into effect this December, the tariffs could benefit producers like Swift and Cubic, which plan to manufacture silicon cells domestically, while potentially raising costs for companies like Tandem that hope to simply source the cheapest, most efficient silicon available on the market.

At any rate, perovskites give the U.S. a chance to secure a domestic supply chain for the next wave of solar tech. Because while Chinese perovskite producers are setting efficiency records, Wharton told me that they tend to be quieter on the question of durability. That could easily give a Western producer with a credible, multi-decade warranty the opportunity to jump to the front of the pack.

And that may happen sooner than you’d expect. “This always follows the same pattern,” Wharton said of technology breakthroughs generally. “You have a bunch of early entrepreneurs who overhype things, and then everybody goes, Yeah, that was a bunch of BS. And then it actually gets real, and then people go, It’s real, but it’s going to take forever. But then it doesn’t take forever because economics always wins.”