Stability of perovskite solar cells boosted with innovative protective layer

by Clarence Oxford

Los Angeles CA (SPX) Nov 22, 2024

Scientists at Northwestern University have unveiled a new protective coating that dramatically improves the longevity of perovskite solar cells, a key step toward making these cells viable for real-world applications.

Perovskite solar cells offer greater efficiency and lower costs compared to traditional silicon-based cells. However, their lack of durability has historically hindered widespread adoption. Conventional coatings using ammonium-based compounds, while effective at enhancing efficiency, degrade quickly under environmental stresses such as heat and moisture.

To address this limitation, the research team introduced an amidinium-based protective layer, which outperformed ammonium coatings by a significant margin. Laboratory tests revealed that this innovative layer is 10 times more resistant to decomposition. Moreover, it tripled the cells’ T90 lifetime – the duration before a cell’s efficiency drops to 90% of its initial level under extreme conditions.

“The field has been working on the stability of perovskite solar cells for a long time,” said Bin Chen, a co-leader of the study. “So far, most reports focus on improving the stability of the perovskite material itself, overlooking the protective layers. By improving the protective layer, we were able to enhance the solar cells’ overall performance.”

Published in ‘Science’, the study marks a critical advancement in perovskite solar cell technology.

“This work addresses one of the critical barriers to widespread adoption of perovskite solar cells – stability under real-world conditions,” explained Mercouri Kanatzidis, another study co-leader. “By chemically reinforcing the protective layers, we’ve significantly advanced the durability of these cells without compromising their exceptional efficiency, bringing us closer to a practical, low-cost alternative to silicon-based photovoltaics.”

Bridging the Durability Gap

Although silicon remains the most widely used material for solar cells due to its reliability and durability, it is costly to produce and nearing its maximum efficiency potential. Researchers have turned to perovskites as a more affordable, higher-efficiency alternative. However, perovskite’s limited lifespan under sunlight, temperature fluctuations, and moisture has remained a major challenge.

The Northwestern team tackled this issue by using amidinium ligands, stable molecules capable of interacting with perovskites to enhance protection and prevent defects. Compared to ammonium-based molecules, amidinium compounds are more structurally resilient under harsh conditions.

“State-of-the-art perovskite solar cells typically have ammonium ligands as a passivation layer,” said Yi Yang, the study’s first author. “But ammonium tends to break down under thermal stress. We did some chemistry to convert the unstable ammonium into a more stable amidinium.”

This transformation, achieved through a chemical process called amidination, replaced the ammonium group with amidinium, preventing degradation and improving thermal stability.

Record-Setting Performance

With this innovation, the perovskite solar cells achieved an efficiency of 26.3%, converting 26.3% of sunlight into usable electricity. Additionally, the amidinium-coated cells maintained 90% of their initial efficiency after 1,100 hours of rigorous testing under heat and light, demonstrating their vastly improved durability.

These results build on previous advancements from Northwestern’s research team. Over the past two years, the Sargent lab has achieved record-breaking energy efficiency, introduced inverted perovskite structures, and incorporated liquid crystals to enhance cell performance.

“Perovskite-based solar cells have the potential to contribute to the decarbonization of the electricity supply once we finalize their design, achieve the union of performance and durability, and scale the devices,” said Ted Sargent, co-leader of the study. “The primary barrier to the commercialization of perovskite solar cells is their long-term stability. But due to its multi-decade head start, silicon still has an advantage in some areas, including stability. We are working to close that gap.”

The study supports the Trienens Institute’s Generate pillar, which focuses on advancing solar energy production through innovative technologies. By improving perovskite solar cells, Northwestern aims to develop the next generation of efficient, cost-effective solar solutions.

Research Report:Amidination of ligands for chemical and field-effect passivation stabilizes perovskite solar cells

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A nonflammable battery to power a safer, decarbonized future

by Zach Winn | MIT News

Boston MA (SPX) Nov 22, 2024

Lithium-ion batteries are the workhorses of home electronics and are powering an electric revolution in transportation. But they are not suitable for every application.

A key drawback is their flammability and toxicity, which make large-scale lithium-ion energy storage a bad fit in densely populated city centers and near metal processing or chemical manufacturing plants.

Now Alsym Energy has developed a nonflammable, nontoxic alternative to lithium-ion batteries to help renewables like wind and solar bridge the gap in a broader range of sectors. The company’s electrodes use relatively stable, abundant materials, and its electrolyte is primarily water with some nontoxic add-ons.

“Renewables are intermittent, so you need storage, and to really solve the decarbonization problem, we need to be able to make these batteries anywhere at low cost,” says Alsym co-founder and MIT Professor Kripa Varanasi.

The company believes its batteries, which are currently being tested by potential customers around the world, hold enormous potential to decarbonize the high-emissions industrial manufacturing sector, and they see other applications ranging from mining to powering data centers, homes, and utilities.

“We are enabling a decarbonization of markets that was not possible before,” Alsym co-founder and CEO Mukesh Chatter says. “No chemical or steel plant would dare put a lithium battery close to their premises because of the flammability, and industrial emissions are a much bigger problem than passenger cars. With this approach, we’re able to offer a new path.”

Helping 1 billion people

Chatter started a telecommunications company with serial entrepreneurs and longtime members of the MIT community Ray Stata ’57, SM ’58 and Alec Dingee ’52 in 1997. Since the company was acquired in 1999, Chatter and his wife have started other ventures and invested in some startups, but after losing his mother to cancer in 2012, Chatter decided he wanted to maximize his impact by only working on technologies that could reach 1 billion people or more.

The problem Chatter decided to focus on was electricity access.

“The intent was to light up the homes of at least 1 billion people around the world who either did not have electricity, or only got it part of the time, condemning them basically to a life of poverty in the 19th century,” Chatter says. “When you don’t have access to electricity, you also don’t have the internet, cell phones, education, etc.”

To solve the problem, Chatter decided to fund research into a new kind of battery. The battery had to be cheap enough to be adopted in low-resource settings, safe enough to be deployed in crowded areas, and work well enough to support two light bulbs, a fan, a refrigerator, and an internet modem.

At first, Chatter was surprised how few takers he had to start the research, even from researchers at the top universities in the world.

“It’s a burning problem, but the risk of failure was so high that nobody wanted to take the chance,” Chatter recalls.

He finally found his partners in Varanasi, Rensselaer Polytechnic Institute Professor Nikhil Koratkar and Rensselaer researcher Rahul Mukherjee. Varanasi, who notes he’s been at MIT for 22 years, says the Institute’s culture gave him the confidence to tackle big problems.

“My students, postdocs, and colleagues are inspirational to me,” he says. “The MIT ecosystem infuses us with this resolve to go after problems that look insurmountable.”

Varanasi leads an interdisciplinary lab at MIT dedicated to understanding physicochemical and biological phenomena. His research has spurred the creation of materials, devices, products, and processes to tackle challenges in energy, agriculture, and other sectors, as well as startup companies to commercialize this work.

“Working at the interfaces of matter has unlocked numerous new research pathways across various fields, and MIT has provided me the creative freedom to explore, discover, and learn, and apply that knowledge to solve critical challenges,” he says. “I was able to draw significantly from my learnings as we set out to develop the new battery technology.”

Alsym’s founding team began by trying to design a battery from scratch based on new materials that could fit the parameters defined by Chatter. To make it nonflammable and nontoxic, the founders wanted to avoid lithium and cobalt.

After evaluating many different chemistries, the founders settled on Alsym’s current approach, which was finalized in 2020.

Although the full makeup of Alsym’s battery is still under wraps as the company waits to be granted patents, one of Alsym’s electrodes is made mostly of manganese oxide while the other is primarily made of a metal oxide. The electrolyte is primarily water.

There are several advantages to Alsym’s new battery chemistry. Because the battery is inherently safer and more sustainable than lithium-ion, the company doesn’t need the same safety protections or cooling equipment, and it can pack its batteries close to each other without fear of fires or explosions. Varanasi also says the battery can be manufactured in any of today’s lithium-ion plants with minimal changes and at significantly lower operating cost.

“We are very excited right now,” Chatter says. “We started out wanting to light up 1 billion people’s homes, and now in addition to the original goal we have a chance to impact the entire globe if we are successful at cutting back industrial emissions.”

A new platform for energy storage

Although the batteries don’t quite reach the energy density of lithium-ion batteries, Varanasi says Alsym is first among alternative chemistries at the system-level. He says 20-foot containers of Alsym’s batteries can provide 1.7 megawatt hours of electricity. The batteries can also fast-charge over four hours and can be configured to discharge over anywhere from two to 110 hours.

“We’re highly configurable, and that’s important because depending on where you are, you can sometimes run on two cycles a day with solar, and in combination with wind, you could truly get 24/7 electricity,” Chatter says. “The need to do multiday or long duration storage is a small part of the market, but we support that too.”

Alsym has been manufacturing prototypes at a small facility in Woburn, Massachusetts, for the last two years, and early this year it expanded its capacity and began to send samples to customers for field testing.

In addition to large utilities, the company is working with municipalities, generator manufacturers, and providers of behind-the-meter power for residential and commercial buildings. The company is also in discussion with a large chemical manufacturers and metal processing plants to provide energy storage system to reduce their carbon footprint, something they say was not feasible with lithium-ion batteries, due to their flammability, or with nonlithium batteries, due to their large space requirements.

Another critical area is data centers. With the growth of AI, the demand for data centers – and their energy consumption – is set to surge.

“We must power the AI and digitization revolution without compromising our planet,” says Varanasi, adding that lithium batteries are unsuitable for co-location with data centers due to flammability risks. “Alsym batteries are well-positioned to offer a safer, more sustainable alternative. Intermittency is also a key issue for electrolyzers used in green hydrogen production and other markets.”

Varanasi sees Alsym as a platform company, and Chatter says Alsym is already working on other battery chemistries that have higher densities and maintain performance at even more extreme temperatures.

“When you use a single material in any battery, and the whole world starts to use it, you run out of that material,” Varanasi says. “What we have is a platform that has enabled us to not just to come up with just one chemistry, but at least three or four chemistries targeted at different applications so no one particular set of materials will be stressed in terms of supply.”

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Department of Mechanical Engineering

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More energy and oil possible through combining photovoltaic plants with hedgerow olive groves

by Hugo Ritmico

Madrid, Spain (SPX) Nov 20, 2024

The integration of photovoltaic plants on agricultural land has long sparked debate over balancing energy production with crop cultivation. Now, the innovative approach of combining both has gained momentum with promising results. This “agrivoltaic” system, which involves placing solar panels within agricultural setups, has been examined by a University of Cordoba research team to see if solar energy and agricultural production could mutually enhance each other.

The research group, including Marta Varo Martinez, Luis Manuel Fernandez de Ahumada, and Rafael Lopez Luque from the Physics for Renewable Energies and Resources group, along with Alvaro Lopez Bernal and Francisco Villalobos from the Soil-Water-Plant Relations group, developed a model that simulates an agrivoltaic system in hedgerow olive plantations. This simulation model combined predictions for oil yield from olive hedgerows and energy generation from solar collectors to assess combined productivity. The study concluded that using both in tandem increased overall productivity, marking a potential shift in land-use strategy that could cater to the needs for both clean energy and food.

The key findings show that mutual benefits arise when solar panels provide shade, acting as windbreaks that don’t compete for water, enhancing agricultural production. Meanwhile, the cooling effect from plant evapotranspiration can improve the efficiency of solar collectors by reducing their temperature, boosting energy output.

This model allows researchers to experiment with various collector configurations, adjusting heights, widths, and spacing, to pinpoint the most effective designs. Despite generally positive outcomes, the team noted that overly dense arrangements might limit space for machinery or complicate maintenance of the olive grove. The approach underscores the importance of balancing land-use density and operational accessibility.

Research Report:Simulation model for electrical and agricultural productivity of an olive hedgerow Agrivoltaic system

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University of Cordoba

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