Scaling up perovskite: Will the US have the last word in ‘transforming the solar market’?

Europe has a number of research centres and collaborations working on the technology, and universities in the Middle East and across Asia have posted efficiency results. Chinese manufacturers have also been moving into the space.

This article will look at the US and more specifically two companies which spoke to PV Tech Premium about their perovskite research plans which raise both optimism and questions about the prospect of perovskite being commercialised in the US.

The road ahead

Perovskite can convert a different set of light rays into electricity than silicon can, and the combination of the two has the potential to greatly increase the efficiency of solar PV and, according to some in the solar industry, revolutionise the way the world produces electricity.

Upstream US-based solar manufacturer CubicPV might feasibly be the place at which tandem perovskite PV products are successfully made durable enough for commercial use; two recent announcements have come out of the company that speaks to the potential of its tandem development route.

The first, financially smaller, was the announcement of CubicPV as the industry partner to the researchers at the Massachusetts Institute of Technology’s (MIT) ADDEPT centre, which was established earlier this year with funding from the US Department of Energy (DOE). The centre is focused on creating stable and commercially transferrable perovskite tandem modules and received US$11.25 million to do so.

Adam Lorenz, CTO of CubicPV told PV Tech Premium: “The financing to establish the ADDEPT center at MIT is an important example of public/private sector collaboration at work and it’s vital to any R&D effort.”

Research centres and consortia exist elsewhere; Qcells and Helmhotz-Zentrum Berlin (HZB) established the PEPPERONI consortium in Europe last year, funded in part by the EU’s Horizon Europe R&D fund, and private institutions like Oxford PV in the UK or various university research teams in the Middle East and elsewhere are working on their own tandem perovskite schemes. Qcells announced its own separate US$100 million investment into a pilot production line in Korea last month.

Lorenz said upon the launch of the ADDEPT project, however, that it may differ in its efficacy: “Instead of chasing record efficiencies with tiny pixel-sized devices and later attempting to stabilize them, we will simultaneously target stability, reproducibility, and efficiency.”

Speaking to PV Tech Premium, Lorenz added: “The current approach to create stable and efficient perovskite device layers is time consuming and requires painstaking rounds of design iteration and testing. The DOE is helping to address the challenge with the funding of ADDEPT, which introduces a stability and performance framework that is guided by machine learning and high throughput experimentation. The expectation is that this will significantly accelerate the transfer of key findings into commercial manufacturing environments.”

The latest round of trade shows, in particular SNEC and Intersolar Europe, have also seen the big manufacturers bring perovskite tandem cells to show and tell. Notably, LONGi unveiled a 33.5% efficiency, 2278mm × 1134mm cell at Intersolar which it says its 4,000-strong R&D team brought from concept to reality in 6 months.

Despite the scale of a company like LONGi’s operations, CubicPV’s second announcement might prove to be a first real acid test for perovskite tandem production.

In June, it announced the first tranche of US$103 million in VC funding to support its tandem research and the development of a 10GW US wafer plant. Whilst Cubic currently produces p-type and n-type mono silicon wafers, this facility plan and the company’s explicit, open discussion of the production of tandem products might result in forays into producing actual commercial perovskite tandem products in the not-too-distant future.

The company has certainly received credible backing so far. The most recent round of funding included contributions from Breakthrough Energy Ventures, a firm founded by Bill Gates, and one of Southeast Asia’s largest conglomerates in SCG Group. Also, the initial funding at CubicPV’s inception included a contribution from US thin film manufacturing giant First Solar.

Cubic’s board of directors page on their website reads well, too, with faces like First Solar veteran Bruce Sohn and CEO Frank Van Mierlo, who previously founded MIT solar wafer spinoff 1366 Technologies and Bluefin Robotics Corporation, as well as having given some public-facing TED talks on the future of tandem PV.

The next junction…

In general, silicon will form the base layer of a tandem cell, with perovskites of different types and configurations deposited on top. The two materials absorb different bands of light and can thus create a higher overall power conversion efficiency for a module.

Of CubicPV’s approach to perovskite, Lorenz said: “Cubic’s approach to silicon/perovskite tandem is to focus on the most durable compositions and interfaces that can deliver long term outdoor reliability for 20+ years.”

He continued: “Our approach to the pairing is what’s called a four terminal or 4T design. This architecture allows us to decouple the two materials in order to address the gap in durability perovskite has relative to silicon. A 4T approach enables more design freedom for the perovskite stack as you’re not constraining the top cell to the parameters of traditional silicon PV manufacturing. Additionally, the top and bottom circuits can still be combined at the module level which provides an elegant alternative to matching current density.”

Perovskite has a tendency to degrade quickly when faced with light and heat, which has been the primary barrier to deployment at any industrial scale. The high efficiencies achieved on postage stamp-sized cells soon fade away when spread over larger areas or brought outside the lab. Lorenz said that CubicPV aims to overcome this with more stringent testing:

“Durability remains the most significant challenge for the perovskite industry: most of the results achieved/literature published are not representative of performance in real world environments where the combination of light and heat leads to ion migration that induces degradation mechanisms. Cubic is generally more aggressive with respect to durability testing, and we measure durability with equal priority to efficiency. Our testing platform stress tests via accelerated aging tests that utilize elevated temperatures of at least 75°C simultaneous with high-intensity illumination – conditions that are relevant for field operations in desert climates.”

What other benefits does Cubic see for perovskites?

“Perovskite photovoltaics are in line with the world’s sustainability goals not only because of the photons they harvest but because they require less embedded energy to produce and have a much lower carbon dioxide equivalent than conventional silicon technology,” Lorenz said. “Additionally, they have a high degree of manufacturability meaning they’re easy to make in large quantities from earth-abundant raw materials.”

Paul Warley, CEO of US flexible thin film solar company Ascent Solar, said similarly: “[perovskite] is less expensive to manufacture than traditional thin film…which expands our horizons. Near-term you could put it on a roof, which would allow us to compete against the panels.”

Ascent Solar makes flexible and semi-flexible solar products, rather than traditional panels, and has recently pivoted to a greater focus on perovskite development. Its Thornton, Colorado base which previously housed its manufacturing headquarters has been converted into a ‘Perovskites Center of Excellence’, looking to develop layered perovskite technology on flexible thin film for niche solar deployments like building integrated PV, drones and unmanned aircraft and, most notably, space travel.

The blind spot?

Paul Warley spoke to PV Tech Premium about the centre, which became a viable option when the company bought Swiss thin film manufacturer Flisom’s production assets. Research will now be taking place at the Colorado site.

“With perovskite you would start off with cells and centimetre by centimetre you would move to whatever type of size you want,” Warley said. “We would want to be on either nine or 12 inches by 36 inches, which would mimic the panels they would put in space.”

The argument is simple: thin film is light and perovskite is efficient, so it suits space travel that requires light and powerful resources. Beyond this, Ascent said fairly little about how they would actually plan to progress tandem research. Warley said that the main barriers to commercial perovskite deployment were: “Getting those multiple perovskite levels [in a cell] to work with light bands, and money.”

The company was unwilling to comment on any forecast or future plans and didn’t elaborate on the specifics of the work being done at the ‘center of excellence’. Perovskite efficiency announcements and development plans often sound impressive, but the framework around measuring efficiencies and tracking progress to commercialisation isn’t there to be enforced.

In an attempt to combat this and push industry-wide progression, Fraunhofer ISE recently launched a perovskite testing system in Europe designed to add uniformity and tracking to the efficiencies that are being reported, in order to create genuine competition. The ‘Katana project’ would subject cells to a broad spectrum of wavelengths organised over 40 different light sources, which Fraunhofer said can bring focus to perovskite efficiency evaluations and accurately test them under strenuous conditions.

A piece by the Independent in the UK last week said that perovskite products were entering production at a startup factory in China and were ‘suitable for commercial use’, but even if successful this will likely be for fringe deployments on scales too small to make a dent in the larger industry.

Once it’s been produced at a commercial scale, Lorenz said that the first adoption of perovskite tandem modules will likely be in the rooftop sector, particularly in areas of the world where balance of system costs make premium efficiency a priority. Beyond that, as prices fall and availability widens, he said that the technology will start appearing at utility-scale.

It will take a first step like Cubic’s US$103 million in funding to test the waters for commercialisation, which they said will allow them to move quickly in developing silicon wafers in the US and subsequently push their tandem module development.

“We believe the impact will transform the solar market,” Lorenz said. “The introduction of tandem PV allows the industry to create a new trajectory to higher efficiency and avoid stagnation when single junction PV products inevitably hit the efficiency limit imposed by the laws of nature. This, in turn, will accelerate solar’s adoption and make a significant impact in our efforts to transition away from carbon-based fuels.”

If the US is to be the place to commercialise perovskite, CubicPV seems to be a likely candidate. Lorenz said of the tandem research environment in the US: “There is a strong ecosystem and there are numerous companies domestically that are working on tandem innovations. Moreover, because there’s a low threshold to introduction, academia is very involved and there’s a deep pool of universities with active perovskite R&D.

“Our national labs such as NREL are also focused on the technology and bring deep knowledge. The US government most definitely recognizes the potential of perovskite, having awarded dozens of grants to advance the technology, however the level of investment is not as significant as what we’ve seen in Europe and China.”

Ultimately, commercial perovskite is on the cards for the PV industry in one way or another. PV Tech’s news desk has seen perovskite-related stories come more and more frequently over recent months, and CubicPV could well be chief among them, if the big players in China don’t get there first.