Thin-film technologies have long promised to make a significant impact on the solar industry, but have been largely limited to niche applications and research labs if the market doesn’t chip away at them. After several false starts, current commercial dynamics and promising research programs may help solar thin films find their place in the sun.
Thin-film solar energy has long promised a great future, but the scale of the technology has been slow. However, recent innovations and applications point to an opening of the market.
Long-time thin-film maker First Solar’s cadmium telluride (CdTe) technology is currently on its way to silicon PV-type scale thanks to the US Inflationary Restraint Act (IRA) and the construction of a 3.3 GW annual manufacturing facility. in India. US-based First Solar had moved out of India due to competition from Chinese rivals, but has been invited back by the country’s industrialization plans and the global trend of onshore solar production.
The first Solar research institute and the Indian research institute IIT Madras (IITM) Research Park agreed in February to cooperate in R&D, focusing especially on thin films.
Professor Ashok Jhunjhunwala, IITM incubation cell professor and head of the research park, says pv magazine he visited the US in 2017 to persuade First Solar to return to India.
“They didn’t seem interested,” he says. “I was very keen to get them here and for a very simple reason – you can’t let one country dominate a very important technology.”
As India’s industrialization emulates China, it needs energy. “In India, you’re going to see 1,000 GW of solar power one day – that’s the kind of technology we might need,” says Jhunjhunwala.
Silicon PV “requires massive targeting of solar rays,” Jhunjhunwala continues, highlighting the benefits of CdTe in India. The technique works better in the morning and late evening, and in high temperatures and humid conditions. “It’s a very cost-effective… technology,” adds the professor.
Thin film researchers are working on innovations that enable solar integration everywhere. Researchers at the Massachusetts Institute of Technology (MIT) recently announced a scalable manufacturing technique for ultra-thin, lightweight solar cells that can be integrated on, for example, any surface.
The academics separated the manufacturing from the integration of the solar cells, which was demonstrated by attaching the printed module to a strong, fibrous, Kevlar-like Dyneema fabric. Printing cells directly onto fabrics limits them to materials that are chemically and thermally compatible with thin-film processing steps and “decouples solar cell manufacturing from final integration,” the researchers said.
MIT researcher Jeremiah Mwaura says pv magazine that the goal is to “facilitate the manufacturing process to seamlessly integrate PV into fabrics as substrates – ‘fabric PV’.” When manufacturing is decoupled from integration, it is easier to scale by utilizing “the same roll-to-roll tools and carriers that are typically used for large-area printed electronics solution processing.”
The endless applications of printable, prefabricated thin film solar energy range from traditional rooftop installations to the growing demand for additional energy production in products such as sails, tents and awnings. But these will not be realized without large-scale production.
“Many roof spaces require reinforcement to support the weight of conventional solar modules,” says Mwaura. “Imagine having a technology that reduces weight by an order of magnitude, and suddenly a lot more deployment opportunities open up.”
Ease of implementation would revolutionize the industry. If solar electricity were transported in rolls, such as paper or fabric, the costs would be significantly reduced, the barriers to implementation would be reduced and the fragility of the panels would be a thing of the past.
“Although these thin, lightweight solar cells currently have a lower efficiency than traditional silicon cells, they have the potential to excel in applications such as rapid deployment in disaster preparedness and military operations where specific power (amount of electricity produced) rather than efficiency is mission critical,” adds Mwaura.
MIT-developed startup Active Surfaces is eyeing commercialization. With plans to commission a 50 MW production line before 2027, founder and CTO Richard Swartwout believes the solar revolution is heating up.
“We tend to think of the solar market as fully capitalized,” Swartwout said. “But the reality is that from a deployment perspective in the U.S., only 2 percent of buildings have solar. And … the scale of electricity is only producing about 3 to 5 percent of demand in the summer peak, so we’ve got a long way to go.”
Active Surfaces estimates that only 30% of US commercial property can host today’s solar power. Unsuitable surfaces include not only light commercial roofs, but also the membrane roofing common in New England, not to mention roofs whose wind power requires expensive anchoring systems.
With fewer and fewer rooftops in developing countries that can accommodate heavy, glass-encased solar power, MIT’s GridEdge program received funding from the Tata Trusts, the philanthropic arm of India’s Tata Power, to develop scalable solar cell and module infrastructure for developing countries.
“Many villages in rural India don’t have the kind of structural support needed for solar,” says Swartwout. “Another issue is transportation – we had some reports that up to 20-30% of panels transported to rural areas either cracked completely or weakened in the long term due to micro-cracking.
“These are some of the motivating factors to consider an alternative deployment system. Flexible technologies (both organic PV and perovskites) are mechanically more stable. We calculated that using PV rolls, a U-haul could be used to transport up to 1 MW of rated power. This means that… one small truckload a thin film solar roller to a remote village could provide electricity for the entire area.”
Active Surfaces takes advantage of IRA incentives that make U.S. manufacturing “very favorable,” says Swartwout, who hopes to transfer MIT’s solution to custom roll-to-roll tooling within two years. “We’re a roll-to-roll printing company, but we’re not going to use a full-printed stack,” he says. – Many others got lost there. A thin film flexible solar cell like ours is the most optimized commodity of all solar technology because you can always laminate it flat and rigid, but you can never go the other way.
The scaling would represent a breakthrough for solar segments, including photovoltaics integrated into buildings and vehicles, which often feature curved facades. “It’s certainly an interesting time,” Swartwout says. “You wouldn’t have had this motivation to build a thin film 10 years ago.”
Cambridge University researchers have developed a solar-powered “artificial leaf” to produce clean fuels, including hydrogen, from simple ingredients. Researcher Virgil Andrei says photosynthesis influenced the design of ultra-thin, flexible devices.
The tandem device mimics plants “using two light suppressors and two catalysts to perform different types of chemistry,” Andrei says. “We can have, for example, oxygen evolution on the other side and hydrogen evolution or CO2 reduction to synthesis gas or other carbon products on the other side. The advantage of our latest work was that we succeeded in spreading these light suppressors on thin substrates. This offers financial benefits as you can reduce the cost of the entire device, and we also saw new types of functionality.
The device is so light, says Andrei, that “the bubbles that are produced float your leaf on the surface of the water, creating a so-called ‘artificial lotus leaf’ and opening up new spaces for fuel production.”
The artificial leaf is compatible with large-scale production techniques, including roll-to-roll coating. “We wanted to make a technology that can use simple building blocks like water or carbon dioxide2 to make fuels”, Andrei adds. The carbon neutrality of the process could help reduce the industrial production of liquid fuels by petrochemical companies.