When British solar manufacturerOxford PV shipped the first commercial order of perovskite-silicon solar cells last September, it was touted as a breakthrough in the industry. The news marked a milestone in a 15-year global effort to develop this lightweight, versatile material that could outperform traditional silicon solar cells. But the lack of follow-on shipments since then served as a reminder that this technology wasn’t quite ready for mass commercialization.
The main problem: Continued delays in getting perovskites to the solar market has made them less cost–competitive with their establishedpredecessor: silicon solar cells In the time it took the sector to go from the first paper on perovskite-based solar cells in 2009 to the first commercial shipment in 2024, the cost of manufacturing silicon solar cellsplummeted from US $2.11 per watt to as low as $.20 per watt. These prices were driven down largely byincreased production throughout Southeast Asia.
Now, hefty U.S. tariffs on silicon solar imports from these countries could give perovskite manufacturers a competitive edge. The U.S. Department of Commerce on April 21 announced a final decision to levytariffs as high as over 3,400 percent on solar companies in Malaysia, Cambodia, Thailand and Vietnam. The decision is the result of a long-term antidumping and countervailing investigation that found that companies in Chinaattempted to bypass previous levies by moving manufacturing to these four countries.Ifconfirmed by another U.S. agency in June, the levies wouldadd toother U.S. import taxes already in place on solar components from the region.
But the antidumping tariffs don’t apply to thin-film photovoltaics such as perovskites.This could be a boon for those solar developers, but they’re going to have to move quickly. The longer it takes to get perovskites to market, the more the landscape could change. And yet, some researchers in this field continue to focus on breaking power-conversion efficiency records, with some types of perovskite cells reaching 27 percent. These accomplishments might lead to papers in high impact journals, but do little to get perovskites out the door.
Many researchers say it’s time to stop aiming for incremental efficiency gains and instead focus on scaling manufacturing and improving the lifespan of the cells. This would involve developing manufacturing techniques that strike a balance between high quality devices and low production costs.
This won’t be easy. Lowering processing costs while increasing cell lifespan and maintaining reasonably high efficiency will require a lot of research and effort. But if academic and industrial researchers unite, this manufacturing challenge could be solved quicker than one might think.
Perovskite solar cells are composed of organic ions, metals, and halogens that form a special crystal structure that makes them very versatile. With the right composition, perovskites could be better than silicon at converting sunlight to electricity: they have a theoretical efficiency limit of 34 percent, compared with silicon’s 32 percent. They can achieve this with a much thinner layer of material, allowing them to be used in innovative ways such as flexible solar cells, curved solar panels, indoor photovoltaics, and solar windows.
Perovskite developer Tandem PV says perovskite layers produced with solution-based processes don’t have to be made in completely inert conditions. Tandem PV
Perovskites can also be stacked on top of silicon photovoltaics to improve performance. The current record efficiency of perovskite-silicon tandem solar cells stands at 34.6 percent, an impressive 7 percent improvement compared to the best silicon cells.
But manufacturing high quality perovskites at a low cost has proven challenging. Exposure to air and moisture during processing can hinder initial performance and lead to degradation over time. This has forced researchers to assemble them in highly controlled environments.
Within these controlled environments, there are two ways to make perovskite solar cells. The more expensive route—vapor deposition—involves evaporating or vaporizing perovskite materials under vacuum conditions and then depositing them as a thin film. This makes very high-quality films with few defects and reliable efficiency. But the set-up costs for this method are high, and rigorous maintenance and high environmental control is required.
The simpler and cheaper method involves depositing perovskite layers using inkjet printing or spray coating. In these solution-based approaches, perovskite materials are dissolved in a precursor solution or “ink,” and directly applied to the desired surface or substrate. The simplicity of this technique has enabled researchers to rapidly improve perovskites over the past decade. However, these techniques allow plenty of room for contamination and defects to occur.
With either route, to produce the highest-performing cells, fabrication usually happens in a controlled environment such as a laboratory glove box. This equipment pumps out oxygen and moisture, replacing it with a non-reactive gas such as nitrogen. However, increasing the amount of environmental control can drive up costs.
Some glove boxes can bring internal oxygen and moisture levels down to less than 1 part per million (ppm). But installing and maintaining these systems is expensive. This level of environmental control requires a complex loop of filters and blower systems to extract contaminated air, purify it, then recirculate it into the system. These filters and control systems require regular upkeep and replacement, which raise maintenance costs. The ppm sensors alone can cost thousands of dollars.
These maintenance costs will always scale with volume. The larger the environment, the more air that needs to be filtered, and the harder it is to maintain strict environmental control. This necessitates more powerful fans, larger filters, and if these systems are exposed to atmosphere, it will cost more time and money to get them working again.
Innovative Perovskite Fabrication Methods
These challenges have led solar developers to experiment with different fabrication methods for perovskite devices, especially on a larger scale. For example, Power Roll in Durham, England, which is developing flexible solar modules, is currently taking a solution-based approach while simultaneously evaluating other methods. “We continuously collaborate with both industrial and academic partners to stay at the forefront of fabrication techniques. This ensures we keep options open for both vacuum and solution processes,” says Nathan Hill, a senior scientist at Power Roll.
Oxford PV, based in Oxford, England, hasn’tdisclosed how it fabricated the perovskite-silicon tandem modules in its first commercial shipment. In a 2018 interview, Oxford cofounder Henry Snaith hinted that his company might take the vapor route when he said that “vapor-deposited cells [would] advance more quickly than solution-processed cells.”
The spin coating technique deposits perovskite layers using centripetal force to spread material evenly across a substrate. Performing this process inside a glove box, where oxygen and moisture are controlled, helps improve performance. Ossila
Completely inert processing—at very low ppm—isn’t ideal for large scale production, many manufacturers say. So they are exploring innovative approaches to simplify fabrication. “While we acknowledge that processing under inert conditions may be beneficial for lab-scale production, we and our partners find that controlling temperature and humidity are the key factors for managing perovskite grain growth,and have had promising results working outside of inert environments,” says Hill at Power Roll. Another perovskite innovator, Tandem PV in San Jose, Calif., processes its perovskite layers from solutions outside of inert conditions, according to a spokesperson for the company.
As manufacturers continue to experiment, researchers should reevaluate their goals for perovskite solar cells too. Typically, the more inert the environment, the higher performing the solar cell. But how high performing do these cells—and how inert do these environments—really have to be? Is there a middle ground where the environments are partially controlled, and the resulting perovskites are still high-enough quality?
My colleagues and I atOssila have demonstrated that triple-cation mixed-halide perovskites, which are relatively robust, can be reliably made in a glove box that maintains only 15 ppm moisture and 0.5 percent oxygen levels (5000 ppm). These solar cells achieved efficiencies comparable to those made in high-end glove boxes (19.2 percent compared to 19.7 percent, respectively). Devices approaching 19 percent are within the realm of competing with silicon solar technology (which largely achieve 13-23 percent efficiency, depending on the type of solar cell). Because perovskites are best used in situations where silicon cannot be used, or in conjunction with silicon devices, we think this is an impressive result.
We also found that when the same perovskites (triple cation mixed halides) are processed in ambient air with a solution-based approach, devices still performed well. The best results, which reached 17.6 percent, indicate there is hope for good air-processed perovskite solar cells.
Tariffs on Silicon Solar Could Make Perovskites More Competitive
Many academic researchers are also experimenting with creating perovskite solar cells outside of glove box environments. A recent studyin Nature Communications described a solution-processed roll-to-roll perovskite fabricated entirely in ambient air. (Roll-to-roll processing involves high speed manufacturing that can continuously deposit solutions on flexible materials on moving rolls. It’s like newspaper printing, but for solar cells.)
Researchers at Australia’s national science agency, CISRO, last year demonstrated the first entirely roll-to-roll fabricated perovskite solar cell under ambient room conditions. CSIRO
The resulting devices reach efficiencies of 15.5 percent for individual cells and 11 percent for mini-solar modules. What’s more, the estimated production costs are as low as $0.70 per watt and still have further space for cost reductions.
To move the field into full commercialization, it’s critical that more focus be placed on scalable processing methods rather than chasing ever-higher efficiencies. Academia and industry must align their goals of increasing stability and scalability.
Commercialization of perovskite solar cells is within reach. And evolving international trade conditions could give perovskite solar cellsa competitive edge. But to achieve this, it’s extremely important to identify any unnecessary steps involved in making them. With low-costs, globally adaptable production, and flexible manufacturing opportunities, perovskite devices could offer a promising path for manufacturing worldwide, strengthening the overall global supply of photovoltaics.
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