Solar Energy

Researchers improve efficiency of next-generation solar cell material

Published

4 years ago

February 25, 2021

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Researchers improve efficiency of next-generation solar cell material

Perovskites are a leading candidate for eventually replacing silicon as the material of choice for solar panels. They offer the potential for low-cost, low-temperature manufacturing of ultrathin, lightweight flexible cells, but so far their efficiency at converting sunlight to electricity has lagged behind that of silicon and some other alternatives.

Now, a new approach to the design of perovskite cells has pushed the material to match or exceed the efficiency of today’s typical silicon cell, which generally ranges from 20 to 22 percent, laying the groundwork for further improvements.

By adding a specially treated conductive layer of tin dioxide bonded to the perovskite material, which provides an improved path for the charge carriers in the cell, and by modifying the perovskite formula, researchers have boosted its overall efficiency as a solar cell to 25.2 percent – a near-record for such materials, which eclipses the efficiency of many existing solar panels. (Perovskites still lag significantly in longevity compared to silicon, however, a challenge being worked on by teams around the world.)

The findings are described in a paper in the journal Nature by recent MIT graduate Jason Yoo PhD ’20, professor of chemistry and Lester Wolfe Professor Moungi Bawendi, professor of electrical engineering and computer science and Fariborz Maseeh Professor in Emerging Technology Vladimir Bulovic, and 11 others at MIT, in South Korea, and in Georgia.

Perovskites are a broad class of materials defined by the fact that they have a particular kind of molecular arrangement, or lattice, that resembles that of the naturally occurring mineral perovskite. There are vast numbers of possible chemical combinations that can make perovskites, and Yoo explains that these materials have attracted worldwide interest because “at least on paper, they could be made much more cheaply than silicon or gallium arsenide,” one of the other leading contenders. That’s partly because of the much simpler processing and manufacturing processes, which for silicon or gallium arsenide requires sustained heat of over 1,000 degrees Celsius. In contrast, perovskites can be processed at less than 200 C, either in solution or by vapor deposition.

The other major advantage of perovskite over silicon or many other candidate replacements is that it forms extremely thin layers while still efficiently capturing solar energy. “Perovskite cells have the potential to be lightweight compared to silicon, by orders of magnitude,” Bawendi says.

Perovskites have a higher bandgap than silicon, which means they absorb a different part of the light spectrum and thus can complement silicon cells to provide even greater combined efficiencies. But even using only perovskite, Yoo says, “what we’re demonstrating is that even with a single active layer, we can make efficiencies that threaten silicon, and hopefully within punching distance of gallium arsenide. And both of those technologies have been around for much longer than perovskites have.”

One of the keys to the team’s improvement of the material’s efficiency, Bawendi explains, was in the precise engineering of one layer of the sandwich that makes up a perovskite solar cell – the electron transport layer. The perovskite itself is layered with a transparent conductive layer used to carry an electric current from the cell out to where it can be used. However, if the conductive layer is directly attached to the perovskite itself, the electrons and their counterparts, called holes, simply recombine on the spot and no current flows. In the researchers’ design, the perovskite and the conductive layer are separated by an improved type of intermediate layer that can let the electrons through while preventing the recombination.

This middle electron transport layer, and especially the interfaces where it connects to the layers on each side of it, tend to be where inefficiencies occur. By studying these mechanisms and designing a layer, consisting of tin oxide, that more perfectly conforms with those adjacent to it, the researchers were able to greatly reduce the losses.

The method they use is called chemical bath deposition. “It’s like slow cooking in a Crock-Pot,” Bawendi says. With a bath at 90 degrees Celsius, precursor chemicals slowly decompose to form the layer of tin dioxide in place. “The team realized that if we understood the decomposition mechanisms of these precursors, then we’d have a better understanding of how these films form. We were able to find the right window in which the electron transport layer with ideal properties can be synthesized.”

After a series of controlled experiments, they found that different mixtures of intermediate compounds would form, depending on the acidity of the precursor solution. They also identified a sweet spot of precursor compositions that allowed the reaction to produce a much more effective film.

The researchers combined these steps with an optimization of the perovskite layer itself. They used a set of additives to the perovskite recipe to improve its stability, which had been tried before but had an undesired effect on the material’s bandgap, making it a less efficient light absorber. The team found that by adding much smaller amounts of these additives – less than 1 percent – they could still get the beneficial effects without altering the bandgap.

The resulting improvement in efficiency has already driven the material to over 80 percent of the theoretical maximum efficiency that such materials could have, Yoo says.

While these high efficiencies were demonstrated in tiny lab-scale devices, Bawendi says that “the kind of insights we provide in this paper, and some of the tricks we provide, could potentially be applied to the methods that people are now developing for large-scale, manufacturable perovskite cells, and therefore boost those efficiencies.”

In pursuing the research further, there are two important avenues, he says: to continue pushing the limits on better efficiency, and to focus on increasing the material’s long-term stability, which currently is measured in months, compared to decades for silicon cells. But for some purposes, Bawendi points out, longevity may not be so essential. Many electronic devices such as cellphones, for example, tend to be replaced within a few years anyway, so there may be some useful applications even for relatively short-lived solar cells.

“I don’t think we’re there yet with these cells, even for these kind of shorter-term applications,” he says. “But people are getting close, so combining our ideas in this paper with ideas that other people have with increasing stability could lead to something really interesting.”

Robert Hoye, a lecturer in materials at Imperial College London, who was not part of the study, says, “This is excellent work by an international team.” He adds, “This could lead to greater reproducibility and the excellent device efficiencies achieved in the lab translating to commercialized modules. In terms of scientific milestones, not only do they achieve an efficiency that was the certified record for perovskite solar cells for much of last year, they also achieve open-circuit voltages up to 97 percent of the radiative limit. This is an astonishing achievement for solar cells grown from solution.””

The team included researchers at the Korea Research Institute of Chemical Technology, the Korea Advanced Institute of Science and Technology, the Ulsan National Institute of Science and Technology, and Georgia Tech. The work was supported by MIT’s Institute for Soldier Nanotechnology, NASA, the Italian company Eni SpA through the MIT Energy Initiative, the National Research Foundation of Korea, and the National Research Council of Science and Technology.

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Solar Energy

A single molecule elevates solar module output and stability

Published

2 days ago

April 24, 2025

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A single molecule elevates solar module output and stability

by Sophie Jenkins

London, UK (SPX) Apr 24, 2025

A new molecule developed through international collaboration has been shown to significantly improve both the performance and durability of perovskite solar cells, according to a recent study published in *Science*. The discovery centers on a synthetic ionic salt named CPMAC, which originates from buckminsterfullerene (C60) and has been shown to outperform traditional C60 in solar applications.

Researchers from the King Abdullah University of Science and Technology (KAUST) played a key role in the development of CPMAC. While C60 has long been used in perovskite solar cells due to its favorable electronic properties, it suffers from stability issues caused by weak van der Waals interactions at the interface with the perovskite layer. CPMAC was engineered to address these shortcomings.

“For over a decade, C60 has been an integral component in the development of perovskite solar cells. However, weak interactions at the perovskite/C60 interface lead to mechanical degradation that compromises long-term solar cell stability. To address this limitation, we designed a C60-derived ionic salt, CPMAC, to significantly enhance the stability of the perovskite solar cells,” explained Professor Osman Bakr, Executive Faculty of the KAUST Center of Excellence for Renewable Energy and Sustainable Technologies (CREST).

Unlike C60, CPMAC forms ionic bonds with the perovskite material, strengthening the electron transfer layer and thereby enhancing both structural stability and energy output. Cells incorporating CPMAC demonstrated a 0.6% improvement in power conversion efficiency (PCE) compared to those using C60.

Though the gain in efficiency appears modest, the impact scales up dramatically in real-world energy production. “When we deal with the scale of a typical power station, the additional electricity generated even from a fraction of a percentage point is quite significant,” said Hongwei Zhu, a research scientist at KAUST.

Beyond efficiency gains, CPMAC also enhanced device longevity. Under accelerated aging tests involving high heat and humidity over 2,000 hours, solar cells containing CPMAC retained a significantly higher portion of their efficiency. Specifically, their degradation was one third that observed in cells using conventional C60.

Further performance evaluation involved assembling the cells into four-cell modules, offering a closer approximation to commercial-scale solar panels. These tests reinforced the molecule’s advantage in both durability and output.

The key to CPMAC’s success lies in its capacity to reduce defects within the electron transfer layer, thanks to the formation of robust ionic bonds. This approach circumvents the limitations posed by van der Waals forces typical of unmodified C60 structures.

Research Report:C60-based ionic salt electron shuttle for high-performance inverted perovskite solar modules

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Solar Energy

Indonesia says China’s Huayou to replace LGES in EV battery project

Published

2 days ago

April 24, 2025

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Indonesia says China’s Huayou to replace LGES in EV battery project

by AFP Staff Writers

Jakarta (AFP) April 23, 2025

China’s Zhejiang Huayou Cobalt is replacing South Korea’s LG Energy Solution as a strategic investor in a multibillion-dollar project to build an electric vehicle battery joint venture in Indonesia, officials said on Wednesday.

The South Korean company, which was part of a consortium that signed a 142 trillion rupiah ($8.4 billion) “Grand Project” in 2020, announced its withdrawal from the project this week, citing factors including market conditions and the investment environment.

Energy and Mineral Resources Minister Bahlil Lahadalia said LG Energy Solution’s decision would not significantly affect the project, which aims to establish a local electric vehicle battery value chain in Indonesia.

“Changes only occur at the investor level, where LG no longer continue its involvement… and has been replaced by a strategic partner from China, namely Huayou,” Bahlil said in a statement.

“Nothing has changed from the initial goal, namely making Indonesia as the center of the world’s electric vehicle industry.”

Indonesia, home to the world’s largest nickel reserve, has been seeking to position itself as a key player in the global electric vehicle supply chain by leveraging its vast reserve of the critical mineral to attract investments.

The government decided not to move forward with the South Korean company in the project due to the long negotiation process with the firm to realise its investment, Investment Minister Rosan Roeslani said.

Rosan cited Huayou’s familiarity with Indonesia as one of the reasons why the government chose the company to succeed LG Energy Solution.

“Huayou had invested in Indonesia,” Rosan said.

“They have sources to develop the industry going forward.”

LG Energy Solution said in a statement on Tuesday that it will continue to explore “various avenues of collaboration” with the Indonesian government, including in its battery joint venture.

HLI Green Power, a joint venture between LG Energy Solution and Hyundai Motor Group, operates Indonesia’s first electric vehicle battery plant, which was launched in 2024 with a production capacity of up to 10 Gigawatt hours (GWh) of cells annually.

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Solar Energy

Politecnico di Milano explores global potential of agrivoltaics for land use harmony

Published

3 days ago

April 23, 2025

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Politecnico di Milano explores global potential of agrivoltaics for land use harmony

by Erica Marchand

Paris, France (SPX) Apr 23, 2025

A research team from the Politecnico di Milano has presented new insights into how agrivoltaic systems could resolve growing tensions over land use between agricultural production and solar energy development. Led by Maddalena Curioni, Nikolas Galli, Giampaolo Manzolini, and Maria Cristina Rulli, the study demonstrates that integrating photovoltaic panels with crop cultivation can significantly mitigate land-use conflict while maintaining food output.

Published in the journal Earth’s Future, the study highlights that between 13% and 16% of existing ground-mounted solar installations have displaced former farmland, underscoring the competition for arable land. In contrast, the researchers propose that deploying agrivoltaic systems on between 22% and 35% of non-irrigated agricultural land could enable dual use without substantially affecting crop yields.

Using a spatial agro-hydrological model, the researchers simulated how 22 crop types respond to varying degrees of solar shading from photovoltaic panels. Their simulations covered a broad range of climates and geographies, generating a global suitability map for agrivoltaic deployment. The results underscore the feasibility of this approach in many regions, especially those with compatible crops and moderate solar intensity.

“Agrivoltaics cannot be applied everywhere, but according to our results, it would be possible to combine cultivation and energy production in many areas of the world without significant reductions in yield,” said Nikolas Galli, researcher at the Glob3Science Lab and co-author of the study.

Giampaolo Manzolini, professor in the Department of Energy, noted additional benefits: “Using the land for both cultivation and photovoltaic systems increases overall output per occupied surface area while reducing production costs. In addition, installing crops underneath the photovoltaic panels reduces the panel operating temperature and increases their efficiency.”

“This technology could help reduce land competition while improving the sustainability of agricultural and energy systems,” added Maria Cristina Rulli, who coordinated the research.

The team emphasizes that their findings could inform strategic policy decisions and investment strategies aimed at maximizing land productivity while supporting both food security and renewable energy goals.

Research Report:Global Land-Water Competition and Synergy Between Solar Energy and Agriculture