Solar Energy

Solving interface mystery in organic solar cells makes them more efficient

Published

2 days ago

November 19, 2024

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Solving interface mystery in organic solar cells makes them more efficient

by Matt Shipman for NCSU News

Raleigh NC (SPX) Oct 31, 2024

New research from North Carolina State University provides a deeper understanding of precisely what is happening in organic solar cells as light is converted into electricity. Researchers developed a new method which visualizes interfaces where the sunlight’s energy is converted to electrical charges and used the findings to develop a set of design rules that can improve the efficiency of organic solar cells.

Organic solar cells are made with carbon-based polymer materials that have the potential to be low cost, can be made from earth-abundant materials, and have some attractive features – such as the fact that they can be made into semi-transparent or transparent window applications. In addition, as thin film solar cells they have the potential for lightweight and flexible solar applications amenable to roll-to-roll manufacturing – which could also make them easy to transport and install.

However, organic solar cells have not been as efficient as silicon or perovskite solar technologies at converting light into electricity.

“Organic solar cells are made of a mixture of two materials,” says Aram Amassian, co-corresponding author of a paper on the work and a university faculty scholar and professor of materials science and engineering at North Carolina State University.

“Both materials harvest electrons from sunlight. However, one of the materials is a polymer that harvests electrons, but then has to interact with the second material in order to pass those electrons on. The polymer is called a donor material; the other substance, typically a small molecule, is called the acceptor material. We knew that interfaces between donor and acceptor materials were responsible for a voltage loss – which is what currently limits the efficiency of organic solar cells. Our goal with this work was to gain a deeper understanding of what aspects of interfaces were responsible for the voltage loss so that we may improve them.”

To address this challenge, the researchers developed a scanning-probe microscopy method that allowed them to map not only the topographic characteristics of the donor and acceptor blend, but also the energy characteristics of the donor and acceptor materials at the interfaces – such as the energy gradient at the interface and how disordered the donor and acceptor materials are at the interface.

“This technique allowed us to determine how the degree of disorder of donor and acceptor molecules at the interface impacted the energy disorder,” says Daniel Dougherty, co-corresponding author of the paper and a professor of physics at NC State. “Once we had mapped the energetics of all of these interfaces, we were able to compare those findings with the results of conventional methods that characterize the overall performance of an organic solar cell’s voltage loss.”

The team needed to overcome another key challenge. As the scanning-probe microscopy technique does not directly measure voltage loss, the team could not tell which interface was the main culprit.

“Blends of donor and acceptor materials give rise to many different types of interfaces at once and it is not clear which interfaces are responsible for voltage losses,” Amassian says.

“Our study revealed that the functional interface in modern high performance organic solar cells, such as PM6:Y6, is the sharp donor-acceptor interface,” Dougherty says. “The findings imply that this type of interface needs to be targeted to further reduce voltage losses.”

“Once we identified the functional interface associated with voltage loss, we conducted a series of investigations into which factors influenced voltage loss,” Amassian says.

“There has been a longstanding debate in the organic solar cell community between people who argued that voltage loss was driven by energy differential between constituent donor and acceptor materials and people who argued that voltage loss was driven by energetic disorder along interfaces. Our experiments show that both sides are correct – it’s a combination of both factors.”

The researchers successfully demonstrated that it is possible to “fix” the energy differential and tune the disorder at interfaces by changing the way the donor and acceptor are blended during fabrication in such a way as to reduce the voltage loss as much as possible.

“By controlling for one of the drivers of voltage loss, we were actually able to identify engineering solutions that will help the organic solar cell community minimize the other driver of voltage loss,” Amassian says.

“Essentially, voltage losses are reduced by selecting a pair of materials with minimal energy offsets. Practitioners can then further reduce energy losses by identifying a solvent and processing parameters that substantially reduce interfacial disorder. We’re optimistic the design rules we developed using this technique can be used to inform organic solar cell research and development moving forward.”

Research Report:Mapping Interfacial Energetic Landscape in Organic Solar Cells Reveals Pathways to Reducing Nonradiative Losses

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Solar Energy

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

Published

1 day ago

November 20, 2024

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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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Solar Energy

New initiative empowers Native American women with solar training

Published

1 day ago

November 20, 2024

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New initiative empowers Native American women with solar training

by Clarence Oxford

Los Angeles CA (SPX) Nov 20, 2024

Native American women across the country are gaining access to hands-on training in photovoltaic panel installation aimed at empowering them to establish solar systems in their communities and homes on tribal land.

Sandra Begay, an engineer at Sandia National Laboratories and a Navajo Nation member, is one of four mentors guiding this effort.

This training initiative is part of a Cooperative Research and Development Agreement between Sandia and Red Cloud Renewable, a nonprofit organization in Pine Ridge, South Dakota, that focuses on advancing energy independence for tribal members and communities.

Known as the Bridging Renewable Industry Divides in Gender Equality, or BRIDGE, Program, the initiative provides a five-week immersive training experience that emphasizes practical skills in photovoltaic installation.

In August, Begay joined the first group of participants in South Dakota.

“Five weeks is a long time to be away from home,” Begay said. “I provided encouragement and reminded the women that they made the right choice to participate in this program. We also used the time to reflect on what they learned.”

Participants are taught the components of photovoltaic systems and how to install them safely and effectively.

Begay also provided insight into the energy challenges faced by tribal communities.

“There are more than 20,000 homes on the Navajo Nation and some rural homes on the Hopi reservation that don’t have electricity. These are off-grid homes,” Begay said, noting that many of these homes depend on diesel generators. “We’re looking at a clean energy future. We want to move away from those types of fuels and look at clean energy sources such as solar.”

She highlighted that large-scale solar projects are being developed by the Navajo Nation and the Mountain Ute Tribe in Colorado.

“This program will provide participants with new employment opportunities and a better understanding of where we’re headed with clean energy,” Begay said.

Red Cloud Renewable also supports the women with resume building, interview training, networking, and job placement services.

With over 30 years of experience championing renewable energy in Native American communities, Begay is committed to maintaining relationships with participants.

“I am making a long-term commitment to the women in the BRIDGE Program,” Begay said. “I will share any job openings I see with them and support them in their job searches.”

Teamwork for success

Begay emphasized the critical role teamwork plays in photovoltaic installations.

“Photovoltaic installation happens with a team of people. How do you work through that group dynamic? How do you work with each other as a team? Those questions are underemphasized in the work we do. They’re going to rely on each other when installing photovoltaic systems,” she said.

Alicia Hayden, Red Cloud Renewable’s communications manager, noted the strong bond formed among the participants.

“What stood out to me was the incredible camaraderie among the women,” Hayden said. “They were genuinely supportive of each other and grateful to be participating in this program alongside women who share similar backgrounds.”

Funded by the Department of Energy’s Solar Energy Technology Office, the project is set to continue over the next few years and aims to train two additional groups, eventually involving around 45 women.

“These women will be equipped to take on installer jobs within their own reservations, bringing valuable skills and opportunities for sustainable development to their people,” Hayden said.

Despite being highly underrepresented in the solar industry – comprising just 0.05% of the sector, according to Red Cloud Renewable – Native American women stand to gain from this initiative.

Begay expressed optimism about the impact of the BRIDGE Program.

“It’s very gratifying both professionally and personally to see where we can help women who are underrepresented in the workforce, let alone in a unique technology like photovoltaic installation,” Begay said. “We’re seeding ideas for the women that they would never have thought of doing. I think that’s what’s unique.”

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Solar Energy

Perovskite advancements improve solar cell efficiency and longevity

Published

1 day ago

November 20, 2024

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Perovskite advancements improve solar cell efficiency and longevity

by Sophie Jenkins

London, UK (SPX) Nov 20, 2024

A global team led by the University of Surrey, in collaboration with Imperial College London, has pioneered a method to enhance the efficiency and durability of solar cells constructed from perovskite by addressing an unseen degradation pathway.

The University of Surrey’s Advanced Technology Institute (ATI) detailed their findings in ‘Energy and Environmental Science’, showing that by employing specific design strategies, they successfully created lead-tin perovskite solar cells achieving over 23% power conversion efficiency (PCE) – a significant result for this material type. Notably, these improvements also boosted the operational lifespan of these cells by 66%. PCE measures the proportion of sunlight converted to usable energy by a solar cell.

While traditional silicon solar panels are already widely used, advancements are steering towards perovskite/silicon hybrid panels, and fully perovskite-based panels promise even higher efficiencies. However, improving the stability and efficiency of lead-tin perovskite cells remains a significant hurdle. This research by the University of Surrey sheds light on mechanisms contributing to these limitations and offers a pathway to overcoming them, aiding in the broader advancement of solar technology.

Hashini Perera, Ph.D. student and lead author at ATI, stated: “The understanding we have developed from this work has allowed us to identify a strategy that improves the efficiency and extends the operational lifetime of these devices when exposed to ambient conditions. This advancement is a major step towards high efficiency, long-lasting solar panels which will give more people access to affordable clean energy while reducing the reliance on fossil fuels and global carbon emissions.”

The team focused on minimizing losses caused by the hole transport layer, crucial for solar cell functionality. By introducing an iodine-reducing agent, they mitigated the degradation effects, enhancing both the cell’s efficiency and its lifespan. This innovation paves the way for more sustainable and economically feasible solar technology.

Dr. Imalka Jayawardena from the University of Surrey’s ATI, co-author of the study, said: “By significantly enhancing the efficiency of our perovskite-based solar cells, we are moving closer to producing cheaper and more sustainable solar panels. We are already working on refining these materials, processes and the device architecture to tackle the remaining challenges.”

Professor Ravi Silva, Director of the ATI, added: “This research brings us closer to panels that not only generate more power over their lifetime but are also longer lasting. Greater efficiency and fewer replacements mean more green energy with less waste. The University of Surrey are in the process of building a 12.5MW solar farm, where we can test some of these modules. We’re confident that our innovative perovskite research will accelerate the widespread commercial adoption of perovskite-based solar panels.”

This progress aligns with the UN Sustainable Development Goals, specifically Goals 7 (affordable and clean energy), 9 (industry, innovation, and infrastructure), and 13 (climate action).

Research Report:23.2% efficient low band gap perovskite solar cells with cyanogen management