It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Tuesday, September 06, 2022
Nuclear cauldrons: studying star burning with radioactive and neutron beams
Using Earth-based particle accelerators, scientists measure the reactions that take place in stars to produce carbon
DOE/US DEPARTMENT OF ENERGY
image: Schematic showing how neutrons in stars can cause stars to burn more quickly by stealing the energy from carbon as it is freshly created in a highly excited form (called the ‘Hoyle state’) to produce stable carbon in its “ground state."view more
Credit: Image courtesy of Jack Bishop, Texas A&M University
The Science
Researchers have found a new way of measuring the decay of a special configuration of carbon called the “Hoyle state,” an excited form of carbon-12. Since the 1950s, scientists have theorized that carbon-12 would easily form in this state in stars from three helium-4 nuclei, called alpha particles. This carbon-12 in a Hoyle state would then decay to simple ground-state carbon and in the process release energy. One goal of the new experiment was to determine if researchers could reliably see in reverse how the Hoyle state breaks apart into three alpha particles. The researchers then used this method to test the importance of neutron upscattering in the fusing of three alpha-particles to create carbon. Neutron upscattering is where a neutron interacts with a resonance (a vibration) and de-excites it, stealing the resonance’s energy. Scientists have theorized for decades that this process makes stars burn faster than expected.
The Impact
This experiment was the first in the world to use a new type of advanced detector to study the properties of the Hoyle state. The detector has a level of sensitivity that made the previously impossible experiment of measuring the neutron upscattering a reality. The researchers’ analysis of the data from the experiment suggests that upscattering plays a less important role in the formation of carbon in stars than originally thought.
Summary
Measuring reactions that take place within stars is difficult. The necessary high temperatures and densities are impossible to replicate on earth. Therefore, researchers rely on measuring related reactions that can be performed in the lab. The goal of this project was to understand how the presence of neutrons in stars affects the fusing of three alpha-particles (helium nuclei) together to form the Hoyle state of carbon-12. The neutrons can increase how quickly the three alpha-particles fuse together through neutron upscattering. Measuring this reaction in the lab relies on the time reverse of this reaction—breaking apart carbon with neutrons to form three alpha-particles.
The project included researchers from Texas A&M University, Ohio University, Washington University in St. Louis, the University of Birmingham, the Université Paris-Saclay, and the Korean Institute for Basic Science. Using a beam of high-energy neutrons at the Edwards Accelerator Laboratory at Ohio University, the researchers fired neutrons into TexAT, a detector developed and built at the Cyclotron Institute at Texas A&M. The researchers then measured the likelihood of the breakup of carbon-12 into three alpha-particles. They found that the propensity of carbon-12 to break apart into three alpha-particles is lower than previously expected from theoretical models. This indicates that the influence of neutron upscattering on the formation of carbon-12 is smaller than originally expected. This result settles a question that has existed for approximately 50 years on the influence neutron upscattering can have on the way a star burns to create heavier elements.
Funding
This work was supported by the Department of Energy Office of Science, Office of Nuclear Physics; by the National Nuclear Security Administration through the Center for Excellence in Nuclear Training and University Based Research; by the Nuclear Solutions Institute at Texas A&M University; and by the UK STFC Network+.
Characteristics of older forests can buffer effects of climate change for some bird species
CORVALLIS, Ore. – Old-growth forests and managed forests with old-growth characteristics can provide relief from climate change for some bird species, research by the Oregon State University College of Forestry suggests.
The study led by former Oregon State doctoral student Hankyu Kim builds on earlier research led by co-author Matt Betts, a professor in the Department of Forest Ecosystems and Society, that showed that old forests with big trees and a diversity of tree sizes and species can offer refuge to some types of birds threatened by a warming climate.
The latest findings bear important implications on conservation decisions regarding mature forests, the scientists say, and have even greater relevance because of the new Inflation Reduction Act, which calls for increased resources to map and protect the United States’ remaining old-growth forests.
The research, published today in Global Change Biology, looked at forest “microclimates.” Microclimates are local atmospheric conditions, in areas ranging from a few square meters to many square kilometers, that differ from those of the surrounding area.
Microclimates tend to be most pronounced in areas of rugged and varied topography such as coastal areas, islands and mountains like Oregon’s Cascade Range, home to the HJ Andrews Experimental Forest where Kim and Betts did their research.
The OSU scientists and collaborators from Oregon State and the United States Forest Service analyzed eight years of breeding bird abundance information from an HJ Andrews watershed as well as subcanopy temperature readings and ground- and LiDAR-based vegetation data. They concluded that at locations with cooler microclimates, some bird species tended to do better – a phenomenon they describe as the “buffering effect.”
Some species also fared better in places where the forest had more compositional diversity, referred to as the “insurance effect” because diversity helps ensure the presence of the insects the birds feed on when they most need nutrition and energy – during breeding season.
“To my knowledge, this is the first empirical evidence of any microclimate effect on songbird populations, and of the insurance effect on free-ranging birds,” said Kim, now a postdoctoral researcher at the University of Wisconsin-Madison. “Each species may have a slightly different range of thermal optima – the range of thermal conditions they feel comfortable with – and it could be the same for the interaction between forest ecosystems and birds.”
Under the current warming regime, he explained, some birds interact with the forest ecosystem to their benefit, while others will find it hard to breed there because the availability of food has changed for the worse.
CAPTION
chestnut-backed chickadee
CREDIT
Hankyu Kim
The scientists found that for five of the 20 bird species they analyzed, abundance trends tended to be either neutral or less negative in cooler microclimates, and the negative effects of warming on two species were reduced in locations with greater forest compositional diversity.
The five species benefiting from the buffering effect were the Swainson’s thrush, chestnut-backed chickadee, hermit warbler, varied thrush and Wilson’s warbler. The Wilson’s warbler and the red crossbill were the two with statistical evidence of benefiting from the insurance effect.
“If plants leaf out earlier in warm microclimates, causing arthropods to emerge earlier, there is a danger of migratory birds mistiming their breeding with peak food availability,” Betts said. “Since leaf-out timing varies by plant species, forests with more plant diversity often have a longer period of insect availability.”
The other 14 birds in the analyses were the dark-eyed junco, hermit thrush, McGillivray’s warbler, Pacific-slope flycatcher, brown creeper, black-throated gray warbler, golden-crowned kinglet, Hammond’s flycatcher, hairy woodpecker, Pacific wren, red-breasted nuthatch, red-breasted sapsucker, western tanager and yellow-rumped warbler.
Seven of the 20 species showed overall declines in abundance over the eight-year study, 2011-18. Nine showed increases and four did display a detectable trend.
“Trends of abundance of five species declined at greater rates in warmer locations than in cooler areas,” Kim said. “That suggests microclimates within forested landscapes do provide refugia for those species. Declining species that are sensitive to warm conditions, like the Wilson’s warbler, hermit warbler and chestnut-backed chickadee, seemed to benefit the most from refugia effects.”
Betts found it interesting that the study led by Kim – whose results Betts said were “collected independently and more rigorously” than those in the research he led in 2017 – showed the same species in decline and the same species benefiting from forests with old-growth characteristics.
“The earlier paper was less well done because we didn’t measure microclimate directly,” Betts said. “Our hypothesis was that microclimate buffering should work for a high proportion of the declining species. This current paper is the first time that’s been shown.”
Brenda McComb and Sarah Frey of the OSU College of Forestry and David Bell of the Forest Service’s Pacific Northwest Research Station also took part in this research, which was supported by the National Science Foundation.
IMAGE: NEW RESEARCH SHOWS THAT WHILE LOCAL FOOD OUTLETS RECEIVED SIGNIFICANTLY MORE ATTENTION FROM CONSUMERS AS A RESULT OF THE PANDEMIC, THOSE IN THE LOCAL FOOD COMMUNITY SHOULD NOT EXPECT THE ELEVATED INTEREST TO CONTINUE.view more
CREDIT: JOSHUA SCHEINBERG / PENN STATE
The COVID‐19 pandemic affected American households in countless ways, but according to researchers, some of the most tangible shifts are taking place in the food system.
A combination of supply chain issues, tighter budgets, concern about shopping in public spaces, and increases in at-home preparation has led to a greater interest in sourcing food locally, but the question remains how long that interest will last. A team of researchers from Penn State’s Department of Agricultural Economics, Sociology and Education conducted a study to find out.
Their results, recently published in the journal Agribusiness, indicate the boon to local food producers may be short-lived, especially if consumers are feeling a sense of anxiety.
“During the pandemic, food consumption changed and so did the sourcing of that food,” said Martina Vecchi, assistant professor of agricultural economics at Penn State and lead author on the study. “A lot of people started exploring different ways of purchasing food and we wanted to understand the determining factors in their decisions.”
Using an online survey, the researchers asked 1,650 participants to reflect on the pandemic and their willingness to buy food locally. Their results suggest that thinking about the pandemic increased anxiety, reduced a sense of community belonging, and lowered the price premiums that respondents were willing to pay for local fruits, vegetables and meat.
“The main mechanism that drives the decreased willingness to pay for locally produced food is anxiety,” Vecchi said. “We didn't expect this, but managing anxiety might be one of the most important things we can do to protect general health were there to be another health crisis.”
The researchers began the survey by inducing or “priming” a subset of participants to think about the impact of the pandemic on either their personal life, finances and health or on their local community and its members. They found that both prompts or “primes” increased participants’ levels of anxiety, slightly reduced their sense of community, and significantly decreased the hypothetical price premium participants were willing to pay for local food.
“We thought of those as the two mechanisms that could influence the willingness to buy this type of product: anxiety and sense of community,” Vecchi said. “We assumed that as people got more anxious because of the pandemic, they would buy more local food because they thought it was safer. We also thought it might strengthen their sense of community and would therefore reflect a higher willingness to pay for local food.”
The results show a trend in the opposite direction. As anxiety increased, sense of community decreased. Vecchi explains that the rise in local food sales during the pandemic may simply be a byproduct of supply chain issues and fears about supermarkets, not a reflection of permanent changes in consumer behavior.
“It doesn't appear that their actual willingness to invest in local food was higher,” Vecchi said. “Sure, they were paying for local food, just because they felt that was the safest option, but it's not that their actual willingness to pay for it was higher.”
The researchers explained that while local food outlets received significantly more attention from consumers as a result of the pandemic, those in the local food community should not expect the elevated interest to continue.
“My advice to policymakers and farmers is to try and deal with consumers’ anxiety and their sense of community first,” Vecchi said. “We have to solve for that if we want to sustain a vibrant local food economy.”
In addition to Vecchi, the research team includes Edward Jaenicke and Claudia Schmidt of Penn State’s Department of Agricultural Economics, Sociology and Education.
The work was funded by a Rapid Response to COVID‐19 Grant by the College of Agricultural Sciences' Institute for Sustainable Agricultural, Food and Environmental Science and the USDA National Institute of Food and Agriculture and Hatch appropriations.
IMAGE: IN THE WAKE OF UNPRECEDENTED MARKET SHOCKS IN THE FED CATTLE INDUSTRY, RESEARCHERS AT THE UNIVERSITY OF TENNESSEE INSTITUTE OF AGRICULTURE TEAMED UP WITH MISSISSIPPI STATE UNIVERSITY AND TEXAS A&M UNIVERSITY TO ANALYZE THE FACTORS AFFECTING PRICE RANGES IN NEGOTIATED CASH SALES. PHOTO COURTESY UTIA.view more
CREDIT: UNIVERSITY OF TENNESSEE INSTITUTE OF AGRICULTURE
In the wake of unprecedented market shocks in the fed cattle industry, researchers at the University of Tennessee Institute of Agriculture teamed up with Mississippi State University and Texas A&M University to analyze the factors affecting price ranges in negotiated cash sales. The study indicates that additional information from the reported data is needed to better understand the outcomes of increased cash sales. Filling these data gaps could help inform proposed legislation and voluntary industry plans in their efforts to uncover drivers of price variability and ultimately price discovery, which is the process of revealing prices from market transactions.
Market shocks in recent years have increased concerns regarding fed cattle prices. The COVID-19 pandemic exacerbated these concerns when fed cattle prices declined, despite wholesale and retail beef prices reaching new highs. The heightened concerns led to policy proposals meant to increase the volume of negotiated cash sales. Proponents believe that increasing negotiated cash sales would improve price discovery by reversing a thinning market.
In response to reenergized concerns about price discovery, researchers launched this latest study to analyze how volume of head sold, day of the week, sex, grade, weight range and other factors impact price ranges in the negotiated cash market. Study results indicate that negotiated cash price ranges peak on Monday and are lowest on Tuesday, but increase from Wednesday to Friday. Price ranges were also found to increase with an increased volume of trade, until reaching approximately 8,800 head per sale per day, then it starts to slowly decline. Further, the study shows that negotiated cash price ranges were highest in the Iowa/Minnesota market relative to all other areas in the study.
“While the motivation of many proposed policies is that increased negotiated purchase volumes will yield improved price discovery, results from this study suggest that daily higher negotiated cash trade volume is not necessarily associated with reduced volatility or improved price discovery,” said lead researcher Chris Boyer. “However, reported price ranges lack important information needed to fully understand how market information impacts price discovery.”
The study indicates that increased information about how many and what quality of cattle were traded near the high and low prices reported would allow for more precise analyses. Also, more detailed data on the distribution of prices such as the fifteenth and eighty-fifth percentile of daily prices and median price would greatly enhance price discovery.
Project team members include Chris Boyer and Charley Martinez from the Department of Agricultural and Resource Economics, along with Joshua Maples from Mississippi State University and Justin Benavidez from Texas A&M University. Martinez and Boyer provide leadership in the newly launched UT Center of Farm Management, which focuses on farm financial management in Tennessee and the Southeast. For more information, visit farmmanagement.tennessee.edu.
Through its land-grant mission of research, teaching and extension, the University of Tennessee Institute of Agriculture touches lives and provides Real. Life. Solutions. utia.tennessee.edu.
Argonne puts climate impact in cities under the microscope with new collaborative study
IMAGE: CROCUS WILL CONDUCT NEIGHBORHOOD-SCALE CLIMATE RESEARCH.view more
CREDIT: (IMAGE BY ARGONNE NATIONAL LABORATORY.)
Community Research on Climate and Urban Science will conduct neighborhood-scale climate research aimed at advancing scientific understanding and empowering communities to identify climate and energy solutions for a sustainable future.
The U.S. Department of Energy (DOE) has awarded DOE’s Argonne National Laboratory and a team of academic and community leaders $25 million over five years to advance urban climate science by studying climate change effects at local and regional scales. The results of this new research will inform communities to build resilience to future effects of climate change.
Argonne and partners will establish an Urban Integrated Field Laboratory called Community Research on Climate and Urban Science (CROCUS) focusing on the Chicago region. CROCUS will use community input to identify questions and specific areas of urban climate change to study, ensuring that research results directly benefit local residents. CROCUS researchers will also work with organizations and students to collect on-the-ground data and develop climate models.
“The Chicagoland area provides a rich environment for study and we are excited to work with such a diverse group of community, research and educational partners.” — Cristina Negri, director of Argonne’s Environmental Sciences division and CROCUS lead
Like other U.S. cities, Chicago is already experiencing disruption from climate change in the form of extreme weather, flooding, drought and heat waves. Unfortunately, the neighborhoods that are most at risk for climate-related disasters have historically been understudied and unable to access the resources or services they need. That’s why CROCUS has strong representation from local organizations to develop its research goals.
Researchers will measure Chicago’s temperature, precipitation and soil conditions. They will explore how trees, open spaces, buildings, expressways and Lake Michigan are shaping the city’s climate, as well as how the Chicago area influences climate regionally. And because no two communities are alike, the study will create more detailed climate models than ever before to reveal the effects of climate change on individual neighborhoods. Instead of looking at the climate of the entire region or city as a whole, researchers will be able to predict how climate will evolve at a much smaller scale — even down to street level. This will help communities identify and vet solutions that will make their neighborhoods resilient against the effects of a changing climate.
“The Chicagoland area provides a rich environment for study and we are excited to work with such a diverse group of community, research and educational partners,” said Cristina Negri, director of Argonne’s Environmental Sciences division and CROCUS lead. “The climate here is noticeably changing. Through CROCUS, we can all join forces to understand the underlying processes and provide science-based information. This will help local planners enact solutions leading to an equitable and effective transition to a resilient and carbon-efficient future for all communities.”
Collaboration is central to CROCUS’s work in Chicago. Argonne is partnering with local, regional and national colleges and universities who will recruit and train the next generation of climate and environmental researchers. To address the underrepresentation of people of color in this field of study, the CROCUS collaborative includes minority-serving institutions and historically black colleges and universities. CROCUS academic partners include:
This study focuses on climate change at the neighborhood level, so the research team includes community-based organizations on Chicago’s South and West Sides. This unique collaboration will empower community members to share their needs and concerns, ensuring that researchers deliver information critical to neighborhoods as they transition to clean energy and green infrastructure. Community partners include:
While Chicago is the center of this study, the new insights and lessons learned will help researchers create a blueprint to assist other cities across the country and around the world as they work to become climate change resilient.
“If we understand how climate and urban systems interact at increasingly detailed scales, we can address the challenge in a fair, equitable and sustainable way,” Negri said. “By advancing the science, we can help neighborhoods, governments and communities envision a climate-ready future. We’re all in this together.”
CROCUS is funded by the Biological and Environmental Research program in the DOE’s Office of Science.
The Argonne Leadership Computing Facility provides supercomputing capabilities to the scientific and engineering community to advance fundamental discovery and understanding in a broad range of disciplines. Supported by the U.S. Department of Energy’s (DOE’s) Office of Science, Advanced Scientific Computing Research (ASCR) program, the ALCF is one of two DOE Leadership Computing Facilities in the nation dedicated to open science.
Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science.
The U.S. Department of Energy’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit https://energy.gov/science.
DOE announces $66 million to research the impact of climate change on America's urban communities
Field labs in Baltimore, Chicago, and Texas will study the impact of extreme weather on people, homes, and local infrastructure
WASHINGTON, D.C. — The U.S. Department of Energy (DOE) today announced $66 million in funding for three projects, together involving over 20 institutions, that will develop Urban Integrated Field Laboratories (Urban IFLs) in Baltimore, MD, Chicago, IL, and the Texas Gulf Coast. These Urban IFLs will expand the understanding of climate and weather events and their impact on urban systems, including diverse demographic characteristics; differing climate-induced pressures on people and infrastructures; and varied geographic settings. Understanding how climate change will impact urban systems and infrastructure is key to building resilient cities powered by clean energy, helping achieve President Biden’s goal of a net-zero carbon economy by 2050.
“Understanding the risks of climate change and extreme weather means understanding the direct and indirect effects on people, their homes, their businesses, and the communities they live in,” said U.S. Secretary of Energy Jennifer Granholm. “The Urban Integrated Field Labs will strengthen DOE leadership in climate modeling and drive scientific breakthroughs to inform the development of resilience technology that can protect America’s diverse communities.”
Each Urban IFL project team brings together scientific expertise from multiple institutions with a breadth of expertise in field observations, data assimilation, modeling, and model-data fusion to study the environmental, ecological, infrastructural, and human components of their selected urban regions. The selected projects will advance our scientific understanding of urban systems and harness that understanding to inform equitable climate and energy solutions, strengthening community scale resilience in urban landscapes, and addressing climate change impacts on underrepresented and disadvantaged communities.
The three selected projects will work in three different urban regions that are facing different environmental and climate hazards, and that each have distinct and diverse disadvantaged populations. Each selected IFL includes significant participation from local and minority serving institutions and will provide new opportunities at these institutions to inspire, train, and support leading scientists who have an appreciation for the global climate and energy challenges of the 21st century. The Urban IFLs will serve as an important element of DOE Office of Science’s commitment to the “Justice 40” initiative, which prioritizes investment in diverse and underrepresented communities affected by a changing climate.
The Urban IFL projects include:
Chicago, IL, the 3rd largest city in the nation, led by Argonne National Laboratory, will employ a network of observations and modeling from street to regional scales to explore multiple issues, including mitigation via green roofs and blue spaces, and community-driven future scenarios for adaptation and decarbonization.
Austin, TX, led by the University of Texas at Austin in Beaumont/Port Arthur Texas, focuses on specific challenges of industrialized, medium sized port cities, including significant legacies of petrochemical industry, and how climate change may affect urban flooding and air quality.
Baltimore, MD, led by Johns Hopkins University, focuses on a metropolitan area facing interlinked challenges of aging infrastructure, increased heat and flood risk, and inequitable burdens of air and water pollution that are common to many other mid-sized industrial cities in the Eastern and Midwest United States.
While each project is distinct, each has similarities to other U.S. urban regions and will develop new tools and techniques that will help other cities benefit from the science and success stories of these Urban IFLs.
The projects were selected by competitive peer review under the DOE Funding Opportunity Announcement for Urban Integrated Field Laboratories. Additional selections will be made in fiscal year 2023, subject to the availability of funds.
Total funding is $66 million for projects lasting up to five years in duration, with $18 million in Fiscal Year 2022 dollars and outyear funding contingent on congressional appropriations. The list of projects and more information can be found here.
Major leap for stable high-efficiency perovskite solar cells
Ion-modulated radical doping of spiro-OMeTAD for more efficient and stable perovskite solar cells
IMAGE: FENG WANG, JUNIOR LECTURER AT LINKÖPING UNIVERSITY.view more
CREDIT: ANNA NILSEN
Solar cells manufactured from materials known as “perovskites” are catching up with the efficiency of traditional silicon-based solar cells. At the same time, they have advantages of low cost and short energy payback time. However, such solar cells have problems with stability – something that researchers at Linköping University, together with international collaborators, have now managed to solve. The results, published in Science, are a major step forwards in the quest for next-generation solar cells.
“Our results open new possibilities to develop efficient and stable solar cells. Further, they provide new insights into how the doping of organic semiconductors works,” says Feng Gao, professor in the Department of Physics, Chemistry and Biology (IFM) at Linköping University.
Perovskites are crystalline materials with huge potential to contribute to solving the world’s energy shortage. They are cheap to manufacture, with high efficiency and low weight. However, the perovskite solar cells can degrade quickly, and it has not been possible to build high-efficiency perovskite-based solar cells with the required stability.
“There seems to be a trade-off between high efficiency and stability in perovskite-based solar cells. High-efficiency perovskite solar cells tend to show low stability, and vice versa,” says Tiankai Zhang, a postdoc at IFM and one of the principal authors of the article published in Science.
When solar energy is converted into electricity in perovskite-based solar cells, one or more charge transport layers are usually needed. These lie directly next to the perovskite layer in the solar cell. The organic charge transport layers often need auxiliary molecules in order to function as intended. The material is described as being “doped”.
One doped transport layer called Spiro-OMeTAD is a benchmark in perovskite solar cells, and delivers record power conversion efficiencies. But the present method used to dope Spiro-OMeTAD is slow, and causes the stability issue of perovskite solar cells.
“We have now managed to eliminate the trade-off that has hindered development, using a new doping strategy for Spiro-OMeTAD. This makes it possible for us to obtain both high efficiency and good stability,” says Tiankai Zhang.
Another principal author of the article, Feng Wang, is a junior lecturer at IFM. He points out that perovskite-based solar cells can be used in many ways, and have many areas of applications.
“One advantage of using perovskites is that the solar cells made are thin, which means that they are light and flexible. They can also be semi-transparent. It would be possible, for example, to apply perovskite-based solar cells onto large windows, or building façades. Silicon-based solar cells are too heavy to be used in this way,” says Feng Wang.
The study has been financed by the Swedish Research Council, an ERC Starting Grant, the Knut and Alice Wallenberg Foundation and AFM (the Swedish Government Strategic Research Area in Materials Science on Functional Materials) at Linköping University. Feng Gao is also a Wallenberg Academy Fellow.
CAPTION
Solar cells manufactured from materials known as “perovskites” are catching up with the efficiency of traditional silicon-based solar cells.
Researchers at the U.S. Department of Energy’s (DOE’s) National Renewable Energy Laboratory (NREL) made a technological breakthrough and constructed a perovskite solar cell with the dual benefits of being both highly efficient and highly stable.
The work was done in collaboration with scientists from the University of Toledo, the University of Colorado–Boulder, and the University of California–San Diego.
A unique architectural structure enabled the researchers to record a certified stabilized efficiency of 24% under 1-sun illumination, making it the highest reported of its kind. The highly efficient cell also retained 87% of its original efficiency after 2,400 hours of operation at 55 degrees Celsius.
The paper, “Surface Reaction for Efficient and Stable Inverted Perovskite Solar Cells,” appears in the journal Nature. The authors from NREL are Qi Jiang, Jinhui Tong, Ross Kerner, Sean Dunfield, Chuanxiao Xiao, Rebecca Scheidt, Darius Kuciauskas, Matthew Hautzinger, Robert Tirawat, Matthew Beard, Joseph Berry, Bryon Larson, and Kai Zhu.
Perovskite, which refers to a crystalline structure, has emerged in the last decade as an impressive means to efficiently capture sunlight and convert it to electricity. Research into perovskite solar cells has been focused to a large degree on how to increase their stability.
“Some people can demonstrate perovskites with high stability, but efficiency is lower,” said Zhu, a senior scientist in the Chemistry and Nanoscience Center at NREL. “You ought to have high efficiency and high stability simultaneously. That’s challenging.”
The researchers used an inverted architecture, rather than the “normal” architecture that has to date yielded the highest efficiencies. The difference between the two types is defined by how the layers are deposited on the glass substrate. The inverted perovskite architecture is known for its high stability and integration into tandem solar cells. The NREL-led team also added a new molecule, 3-(Aminomethyl) pyridine (3-APy), to the surface of the perovskite. The molecule reacted to the formamidinium within the perovskite to create an electric field on the surface of the perovskite layer.
“That suddenly gave us a huge boost of not only efficiency but also stability,” Zhu said.
The scientists reported the 3-APy reactive surface engineering can improve the efficiency of an inverted cell from less than 23% to greater than 25%. They also noted the reactive surface engineering stands out as an effective approach to significantly enhance the performance of inverted cells “to new state-of-the-art levels of efficiency and operational reliability.”
Funding for the research done at NREL came from the Center for Hybrid Organic-Inorganic Semiconductors for Energy (CHOISE), an Energy Frontier Research Center within DOE’s Office of Basic Energy Sciences, and from the DOE’s Solar Energy Technologies Office.
NREL is the U.S. Department of Energy's primary national laboratory for renewable energy and energy efficiency research and development. NREL is operated for the Energy Department by the Alliance for Sustainable Energy, LLC.
