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  • richardmitnick 12:23 pm on January 1, 2018 Permalink | Reply
    Tags: , , , , , , Solar cells, Standardizing perovskite aging measurements   

    From EPFL: “Standardizing perovskite aging measurements” 

    EPFL bloc

    École Polytechnique Fédérale de Lausanne

    01.01.18
    Nik Papageorgiou


    EPFL scientists have produced a data-driven proposal for standardizing the measurements of perovskite solar cell stability and degradation. Published in Nature Energy, the work aims to create consensus in the field and overcome one of the major hurdles on the way to commercializing perovskite photovoltaics.

    1
    Perovskite (pronunciation: /pəˈrɒvskaɪt/) is a calcium titanium oxide mineral composed of calcium titanate (CaTiO3). It lends its name to the class of compounds which have the same type of crystal structure as CaTiO3 (XIIA2+VIB4+X2−3), known as the perovskite structure. Many different cations can be embedded in this structure, allowing for the development of diverse engineered materials.
    The mineral was discovered in the Ural Mountains of Russia by Gustav Rose in 1839 and is named after Russian mineralogist Lev Perovski (1792–1856). Perovskite’s notable crystal structure was first described by Victor Goldschmidt in 1926, in his work on tolerance factors. The crystal structure was later published in 1945 from X-ray diffraction data on barium titanate by Helen Dick Megaw. Wikipedia.

    2
    A schematic of a perovskite crystal structure. Clean Energy Institute – University of Washington

    Perovskite solar cells are an alternative to conventional silicon solar cells, and are poised to overtake the market with their high power-conversion efficiencies (over 22% now) and lower capital expenditure and manufacturing costs. But one of the greatest obstacles on this road is stability: to be commercially viable, perovskite solar cells must also be able to maintain their efficiency over time, meaning that they must not degrade significantly over 25 years of service.

    “As a first-order approximation, we are talking about stabilities of several years for the most stable perovskite solar cells,” says Konrad Domanksi, first author on the paper. “We still need an increase of an order of magnitude to reach the stabilities of silicon cells.”

    While research efforts are continuously made to improve perovskite stability, the community is hamstrung by the fact that there are no general standards by which scientists can measure the stability of perovskite solar cells. Consequently, the results coming in from different laboratories and companies cannot be easily compared to each other. And even though dedicated stability measurement standards have been developed for other photovoltaic technologies, they have to be adapted for perovskite solar cells, which show new types of behavior.

    Now, the labs of Michael Grätzel and Anders Hagfeldt at EPFL have carried out a study that proposes to standardize the measurements of perovskite solar cell stability across the entire field. The researchers investigated the effects of different environmental factors on the ageing of perovskite solar cells, looking at the impact of illumination (sunlight-level light), temperature, atmospheric, electrical load, and testing a systematic series of combinations of these.

    “We designed and built a dedicated system to carry out this study,” says Domanski. “It is state-of-the-art for measuring stability of solar cells – we can vary light intensity over samples and control temperature, atmosphere etc. We load the samples, program the experiments, and the data is plotted automatically.”

    The study shows how certain behaviors specific to perovskite solar cells can distort the results of experiments. For example, when the cells are left in the dark, they can recover some of the losses caused by illumination and “start fresh in the morning”. As solar cells naturally undergo day-night cycles, this has important implications on how we define that a solar cell degrades in the first place. It also changes our perception on the metrics used by industry to describe lifetime of solar cells.

    “The work can lay the foundations for standardizing perovskite solar cell ageing,” says Wolfgang Tress, last author on the paper. “The field can use it to develop objective and comparable stability metrics, just like stabilized power is now used as a standard tool for assessing power-conversion efficiency in perovskite solar cells. More importantly, systematically isolating specific degradation factors will help us better understand degradation of perovskite solar cells and improve their lifetimes.”

    “We are not trying to impose standards on the community,” says Domanski. “Rather, being on the forefront on perovskite solar cells and their stability research, we try to lead by example and stimulate the discussion on how these standards should look like. We strongly believe that specific protocols will be adopted by consensus, and that dedicated action groups involving a broad range of researchers will be formed for this purpose.”

    Funding

    Swiss National Science Foundation (FNS)
    King Abdulaziz City for Science and Technology (KACST)

    See the full article here .

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    EPFL is Europe’s most cosmopolitan technical university. It receives students, professors and staff from over 120 nationalities. With both a Swiss and international calling, it is therefore guided by a constant wish to open up; its missions of teaching, research and partnership impact various circles: universities and engineering schools, developing and emerging countries, secondary schools and gymnasiums, industry and economy, political circles and the general public.

     
  • richardmitnick 1:37 pm on June 25, 2017 Permalink | Reply
    Tags: Concentrator photovoltaics, , Molecular beam epitaxy apparatus, Solar cells,   

    From U Michigan: “‘Magic’ alloy could spur the next generation of solar cells” 

    U Michigan bloc

    University of Michigan

    June 15, 2017 [Why so long to get into social media]
    Gabe Cherry

    1
    Jordan Occena, a U-M graduate researcher and Sunyeol Jeon, a former U-M graduate student researcher, calibrate the molecular-beam epitaxy apparatus in the Carl A. Gerstacker Building on August 3, 2015. The apparatus is used for spray painting the “magic” chemical cocktail onto blank gallium arsenide wafers. PHOTO: Joseph Xu, Michigan Engineering.

    In what could be a major step forward for a new generation of solar cells called “concentrator photovoltaics,” a team of University of Michigan researchers has developed a new semiconductor alloy that can capture the near-infrared light located on the leading edge of the visible light spectrum.

    Easier to manufacture and at least 25 percent less costly than previous formulations, it’s believed to be the world’s most cost-effective material that can capture near-infrared light and is compatible with the gallium arsenide semiconductors often used in concentrator photovoltaics.

    Concentrator photovoltaics gather and focus sunlight onto small, high-efficiency solar cells made of gallium arsenide or germanium semiconductors. They’re on track to achieve efficiency rates over 50 percent, while conventional flat-panel silicon solar cells top out in the mid 20s.

    2
    Jordan Occena, a U-M graduate researcher and Sunyeol Jeon, a former U-M graduate student researcher, calibrate the molecular-beam epitaxy apparatus in the Carl A. Gerstacker Building on August 3, 2015. The apparatus is used for spray painting the “magic” chemical cocktail onto blank gallium arsenide wafers. PHOTO: Joseph Xu, Michigan Engineering.

    “Flat-panel silicon is basically maxed out in terms of efficiency,” said Rachel S. Goldman, a U-M materials science and engineering professor whose lab developed the alloy. “The cost of silicon isn’t going down and efficiency isn’t going up. Concentrator photovoltaics could power the next generation.”

    Varieties of concentrator photovoltaics exist today. They are made of three different semiconductor alloys layered together. Sprayed onto a semiconductor wafer in a process called molecular-beam epitaxy—a bit like spray painting with individual elements—each layer is only a few microns thick. The layers capture different parts of the solar spectrum; light that gets through one layer is captured by the next.

    But near-infrared light slips through these cells unharnessed. For years, researchers have been working toward an elusive “fourth layer” alloy that could be sandwiched into cells to capture this light. It’s a tall order; the alloy must be cost-effective, stable, durable and sensitive to infrared light, with an atomic structure that matches the other three layers in the solar cell.

    Getting all those variables right isn’t easy, and until now, researchers have been stuck with prohibitively expensive formulas that use five elements or more.

    3
    The inside of the main concourse of the molecular beam epitaxy apparatus in the Carl A. Gerstacker Building on August 3, 2015. A blank gallium arsenide wafer is placed in this concourse and moves down the tunnel to a growth chamber where the “magic” chemical cocktail is sprayed on. PHOTO: Joseph Xu, Michigan Engineering.

    To find a simpler mix, Goldman’s team devised a novel approach for keeping tabs on the many variables in the process. They combined on-the-ground measurement methods including X-ray diffraction done at U-M and ion beam analysis done at Los Alamos National Laboratory with custom-built computer modeling.

    Using this method, they discovered that a slightly different type of arsenic molecule would pair more effectively with the bismuth. They were able to tweak the amount of nitrogen and bismuth in the mix, enabling them to eliminate an additional manufacturing step that previous formulas required. And they found precisely the right temperature that would enable the elements to mix smoothly and stick to the substrate securely.

    “‘Magic’ is not a word we use often as materials scientists,” Goldman said. “But that’s what it felt like when we finally got it right.”

    4
    A plate of semiconductors made by the molecular beam epitaxy apparatus in the Carl A. Gerstacker Building on August 3, 2015. PHOTO: Joseph Xu, Michigan Engineering.

    The advance comes on the heels of another innovation from Goldman’s lab that simplifies the “doping” process used to tweak the electrical properties of the chemical layers in gallium arsenide semiconductors. During doping, manufacturers apply a mix of chemicals called “designer impurities” to change how semiconductors conduct electricity and give them positive and negative polarity similar to the electrodes of a battery. The doping agents usually used for gallium arsenide semiconductors are silicon on the negative side and beryllium on the positive side.

    The beryllium is a problem—it’s toxic and it costs about ten times more than silicon dopants. Beryllium is also sensitive to heat, which limits flexibility during the manufacturing process. But the U-M team discovered that by reducing the amount of arsenic below levels that were previously considered acceptable, they can “flip” the polarity of silicon dopants, enabling them to use the cheaper, safer element for both the positive and negative sides.

    “Being able to change the polarity of the carrier is kind of like atomic ‘ambidexterity’,” said Richard L. Field, a former U-M PhD student who worked on the project. “Just like people with naturally born ambidexterity, it’s fairly uncommon to find atomic impurities with this ability.”

    Together, the improved doping process and the new alloy could make the semiconductors used in concentrator photovoltaics as much as 30 percent cheaper to produce, a big step toward making the high-efficiency cells practical for large-scale electricity generation.

    “Essentially, this enables us to make these semiconductors with fewer atomic spray cans, and each can is significantly less expensive,” Goldman said. “In the manufacturing world, that kind of simplification is very significant. These new alloys and dopants are also more stable, which gives makers more flexibility as the semiconductors move through the manufacturing process.”

    The new alloy is detailed in a paper titled Bi-enhanced N incorporation in GaAsNBi alloys, published June 15 in Applied Physics Letters. The research is supported by the National Science Foundation (grant number DMR 1410282) and the U.S. Department of Energy Office of Science Graduate Student Research.

    The doping advances are detailed in a paper titled Influence of surface reconstruction on dopant incorporation and transport properties of GaAs(Bi) alloys. It was published in the December 26, 2016 issue of Applied Physics Letters. The research was supported by the National Science Foundation (grant number DMR 1410282).

    See the full article here .

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    U MIchigan Campus

    The University of Michigan (U-M, UM, UMich, or U of M), frequently referred to simply as Michigan, is a public research university located in Ann Arbor, Michigan, United States. Originally, founded in 1817 in Detroit as the Catholepistemiad, or University of Michigania, 20 years before the Michigan Territory officially became a state, the University of Michigan is the state’s oldest university. The university moved to Ann Arbor in 1837 onto 40 acres (16 ha) of what is now known as Central Campus. Since its establishment in Ann Arbor, the university campus has expanded to include more than 584 major buildings with a combined area of more than 34 million gross square feet (781 acres or 3.16 km²), and has two satellite campuses located in Flint and Dearborn. The University was one of the founding members of the Association of American Universities.

    Considered one of the foremost research universities in the United States,[7] the university has very high research activity and its comprehensive graduate program offers doctoral degrees in the humanities, social sciences, and STEM fields (Science, Technology, Engineering and Mathematics) as well as professional degrees in business, medicine, law, pharmacy, nursing, social work and dentistry. Michigan’s body of living alumni (as of 2012) comprises more than 500,000. Besides academic life, Michigan’s athletic teams compete in Division I of the NCAA and are collectively known as the Wolverines. They are members of the Big Ten Conference.

     
  • richardmitnick 4:59 pm on September 26, 2016 Permalink | Reply
    Tags: , , , , Solar cells   

    From BNL: “Crystalline Fault Lines Provide Pathway for Solar Cell Current” 

    Brookhaven Lab

    September 26, 2016
    Karen McNulty Walsh
    kmcnulty@bnl.gov
    (631) 344-8350
    Peter Genzer
    genzer@bnl.gov
    (631) 344-3174

    New tomographic AFM imaging technique reveals that microstructural defects, generally thought to be detrimental, actually improve conductivity in cadmium telluride solar cells.

    1
    CFN staff scientist Lihua Zhang places a sample in the transmission electron microscope.

    A team of scientists studying solar cells made from cadmium telluride, a promising alternative to silicon, has discovered that microscopic “fault lines” within and between crystals of the material act as conductive pathways that ease the flow of electric current. This research—conducted at the University of Connecticut and the U.S. Department of Energy’s Brookhaven National Laboratory, and described in the journal Nature Energy—may help explain how a common processing technique turns cadmium telluride into an excellent material for transforming sunlight into electricity, and suggests a strategy for engineering more efficient solar devices that surpass the performance of silicon.

    “If you look at semiconductors like silicon, defects in the crystals are usually bad,” said co-author Eric Stach, a physicist at Brookhaven Lab’s Center for Functional Nanomaterials (CFN). As Stach explained, misplaced atoms or slight shifts in their alignment often act as traps for the particles that carry electric current—negatively charged electrons or the positively charged “holes” left behind when electrons are knocked loose by photons of sunlight, making them more mobile. The idea behind solar cells is to separate the positive and negative charges and run them through a circuit so the current can be used to power houses, satellites, or even cities. Defects interrupt this flow of charges and keep the solar cell from being as efficient as it could be.

    But in the case of cadmium telluride, the scientists found that boundaries between individual crystals and “planar defects”—fault-like misalignments in the arrangement of atoms—create pathways for conductivity, not traps.

    2
    These CTAFM images show a cadmium telluride solar cell from the top (above) and side profile (bottom) with bright spots representing areas of higher electron conductivity. The images reveal that the conductive pathways coincide with crystal grain boundaries. Credit: University of Connecticut.

    Members of Bryan Huey’s group at the Institute of Materials Science at the University of Connecticut were the first to notice the surprising connection. In an effort to understand the effects of a chloride solution treatment that greatly enhances cadmium telluride’s conductive properties, Justin Luria and Yasemin Kutes studied solar cells before and after treatment. But they did so in a unique way.

    Several groups around the world had looked at the surfaces of such solar cells before, often with a tool known as a conducting atomic force microscope. The microscope has a fine probe many times sharper than the head of a pin that scans across the material’s surface to track the topographic features—the hills and valleys of the surface structure—while simultaneously measuring location-specific conductivity. Scientists use this technique to explore how the surface features relate to solar cell performance at the nanoscale.

    But no one had devised a way to make measurements beneath the surface, the most important part of the solar cell. This is where the UConn team made an important breakthrough. They used an approach developed and perfected by Kutes and Luria over the last two years to acquire hundreds of sequential images, each time intentionally removing a nanoscale layer of the material, so they could scan through the entire thickness of the sample. They then used these layer-by-layer images to build up a three-dimensional, high-resolution ‘tomographic’ map of the solar cell—somewhat like a computed tomography (CT) brain scan.


    Assembling the layer-by-layer CTAFM scans into a side-profile video file reveals the relationship between conductivity and planar defects throughout the entire thickness of the cadmium telluride crystal, including how the defects appear to line up to form continuous pathways of conductivity.Credit: University of Connecticut.

    “Everyone using these microscopes basically takes pictures of the ‘ground,’ and interprets what is beneath,” Huey said. “It may look like there’s a cave, or a rock shelf, or a building foundation down there. But we can only really know once we carefully dig, like archeologists, keeping track of exactly what we find every step of the way—though, of course, at a much, much smaller scale.”

    The resulting CT-AFM maps uniquely revealed current flowing most freely along the crystal boundaries and fault-like defects in the cadmium telluride solar cells. The samples that had been treated with the chloride solution had more defects overall, a higher density of these defects, and what appeared to be a high degree of connectivity among them, while the untreated samples had few defects, no evidence of connectivity, and much lower conductivity.

    Huey’s team suspected that the defects were so-called planar defects, usually caused by shifts in atomic alignments or stacking arrangements within the crystals. But the CTAFM system is not designed to reveal such atomic-scale structural details. To get that information, the UConn team turned to Stach, head of the electron microscopy group at the CFN, a DOE Office of Science User Facility.

    “Having previously shared ideas with Eric, it was a natural extension of our discovery to work with his group,” Huey said.

    Said Stach, “This is the exact type of problem the CFN is set up to handle, providing expertise and equipment that university researchers may not have to help drive science from hypothesis to discovery.”

    CFN staff physicist Lihua Zhang used a transmission electron microscope (TEM) and UConn’s results as a guide to meticulously study how atomic scale features of chloride-treated cadmium telluride related to the conductivity maps. The TEM images revealed the atomic structure of the defects, confirming that they were due to specific changes in the stacking sequence of atoms in the material. The images also showed clearly that these planar defects connected different grains in the crystal, leading to high-conductivity pathways for the movement of electrons and holes.

    “When we looked at the regions with good conductivity, the planar defects linked from one crystal grain to another, forming continuous pathways of conductance through the entire thickness of the material,” said Zhang. “So the regions that had the best conductivity were the ones that had a high degree of connectivity among these defects.”

    3
    These transmission electron microscopy images taken at Brookhaven’s CFN reveals how the stacking pattern of individual atoms (bright spots) shifts. The images confirmed that the bright spots of high conductivity observed with CTAFM imaging at UConn occurred at the interfaces between two different atomic alignments (left) and that these “planar defects” were continuous between individual crystals, creating pathways of conductivity (right). The labels WZ and ZB refer to the two atomic stacking sequences “wurtzite” and “zinc blende,” which are the two types of crystal structures cadmium telluride can form. No image credit.

    The authors say it’s possible that the chloride treatment helps to create the connectivity, not just more defects, but that more research is needed to definitively determine the most significant effects of the chloride solution treatment.

    In any case, Stach says that combining the CTAFM technique and electron microscopy, yields a “clear winner” in the search for more efficient, cost-competitive alternatives to silicon solar cells, which have nearly reached their limit for efficiency.

    “There is already a billion-dollar-a-year industry making cadmium telluride solar cells, and lots of work exploring other alternatives to silicon. But all of these alternatives, because of their crystal structure, have a higher tendency to form defects,” he said. “This work gives us a systematic method we can use to understand if the defects are good or bad in terms of conductivity. It can also be used to explore the effects of different processing methods or chemicals to control how defects form. In the case of cadmium telluride, we may want to find ways to make more of these defects, or look for other materials in which defects improve performance.”

    This research was supported by the DOE Office of Energy Efficiency and Renewable Energy (EERE)—including its Sunshot Program—and the DOE Office of Science. The cadmium telluride samples were provided by Andrew Moore of Colorado State University.

    The University of Connecticut’s Institute of Materials Science serves as the heart of materials science research at the University of Connecticut, with a mission of supporting materials research and industry throughout Connecticut and the Northeast. It houses the research labs of more than 30 core faculty, with an overall membership of 120 UConn faculty whose work benefits from the available facilities and expertise.

    See the full article here .

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    BNL Campus

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
    i1

     
  • richardmitnick 10:41 am on August 26, 2015 Permalink | Reply
    Tags: , , , Solar cells,   

    From ars technica: “Quantum dots may be key to turning windows into photovoltaics” 

    Ars Technica
    ars technica

    Aug 26, 2015
    John Timmer

    1
    Some day, this might generate electricity. Flickr user Ricardo Wang

    While wind may be one of the most economical power sources out there, photovoltaic solar energy has a big advantage: it can go small. While wind gets cheaper as turbines grow larger, the PV hardware scales down to fit wherever we have infrastructure. In fact, simply throwing solar on our existing building stock could generate a very large amount of carbon-free electricity.

    But that also highlights solar’s weakness: we have to install it after the infrastructure is in place, and that installation adds considerably to its cost. Now, some researchers have come up with some hardware that could allow photovoltaics to be incorporated into a basic building component: windows. The solar windows would filter out a small chunk of the solar spectrum and convert roughly a third of it to electricity.

    As you’re probably aware, photovoltaic hardware has to absorb light in order to work, and a typical silicon panel appears black. So, to put any of that hardware (and its supporting wiring) into a window that doesn’t block the view is rather challenging. One option is to use materials that only capture a part of the solar spectrum, but these tend to leave the light that enters the building with a distinctive tint.

    The new hardware takes a very different approach. The entire window is filled with a diffuse cloud of quantum dots that absorb almost all of the solar spectrum. As a result, the “glass” portion of things simply dims the light passing through the window slightly. (The quantum dots are actually embedded in a transparent polymer, but that could be embedded in or coat glass.) The end result is what optics people call a neutral density filter, something often used in photography. In fact, tests with the glass show that the light it transmits meets the highest standards for indoor lighting.

    Of course, simply absorbing the light doesn’t help generate electricity. And, in fact, the quantum dots aren’t used to generate the electricity. Instead, the authors generated quantum dots made of copper, indium, and selenium, covered in a layer of zinc sulfide. (The authors note that there are no toxic metals involved here.) These dots absorb light across a broad band of spectrum, but re-emit it at a specific wavelength in the infrared. The polymer they’re embedded in acts as a waveguide to take many of the photons to the thin edge of the glass.

    And here’s where things get interesting: the wavelength of infrared the quantum dots emit happens to be very efficiently absorbed by a silicon photovoltaic device. So, if you simply place these devices along the edges of the glass, they’ll be fed a steady diet of photons.

    The authors model the device’s behavior and find that nearly half the infrared photons end up being fed the photovoltaic devices (equal amounts get converted to heat or escape the window entirely). It’s notable that the devices are small, though (about 12cm squares)—larger panes would presumably allow even more photons to escape.

    The authors tested a few of the devices, one that filtered out 20 percent of the sunlight and one that only captured 10 percent. The low-level filter sent about one percent of the incident light to the sides, while the darker one sent over three percent.

    There will be losses in the conversion to electricity as well, so this isn’t going to come close to competing with a dedicated panel on a sunny roof. Which is fine, because it’s simply not meant to. Any visit to a major city will serve as a good reminder that we’re regularly building giant walls of glass that currently reflect vast amounts of sunlight, blinding or baking (or both!) the city’s inhabitants on a sunny day. If we could cheaply harvest a bit of that instead, we’re ahead of the game.

    Nature Nanotechnology, 2015. DOI: 10.1038/NNANO.2015.178 (About DOIs).

    See the full article here.

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    Ars Technica was founded in 1998 when Founder & Editor-in-Chief Ken Fisher announced his plans for starting a publication devoted to technology that would cater to what he called “alpha geeks”: technologists and IT professionals. Ken’s vision was to build a publication with a simple editorial mission: be “technically savvy, up-to-date, and more fun” than what was currently popular in the space. In the ensuing years, with formidable contributions by a unique editorial staff, Ars Technica became a trusted source for technology news, tech policy analysis, breakdowns of the latest scientific advancements, gadget reviews, software, hardware, and nearly everything else found in between layers of silicon.

    Ars Technica innovates by listening to its core readership. Readers have come to demand devotedness to accuracy and integrity, flanked by a willingness to leave each day’s meaningless, click-bait fodder by the wayside. The result is something unique: the unparalleled marriage of breadth and depth in technology journalism. By 2001, Ars Technica was regularly producing news reports, op-eds, and the like, but the company stood out from the competition by regularly providing long thought-pieces and in-depth explainers.

    And thanks to its readership, Ars Technica also accomplished a number of industry leading moves. In 2001, Ars launched a digital subscription service when such things were non-existent for digital media. Ars was also the first IT publication to begin covering the resurgence of Apple, and the first to draw analytical and cultural ties between the world of high technology and gaming. Ars was also first to begin selling its long form content in digitally distributable forms, such as PDFs and eventually eBooks (again, starting in 2001).

     
  • richardmitnick 11:40 am on August 14, 2015 Permalink | Reply
    Tags: , , Solar cells   

    From Brown: “Brown to lead $4-million solar cell research grant” 

    Brown University
    Brown University

    August 14, 2015
    Kevin Stacey

    1
    A possible advance in solar power. Nitin Padture, left, and engineering graduate student Yuanyuan Zhou examine solar cell film made from perovskite. More must be learned about perovskites before they can be scaled up to mass production. Credit: Amy Simmons

    A team led by Brown University researchers has been awarded $4 million by the National Science Foundation to study a promising new type of solar cell. The research, to be performed in partnership with the University of Nebraska–Lincoln (UNL) and Rhode Island College (RIC), will focus on solar cells made from perovskites, a class of crystalline materials.

    “Perovskites have great promise for use in a variety of highly efficient, low-cost solar cells,” said Nitin Padture, professor in the School of Engineering and director of Brown’s Institute for Molecular and Nanoscale Innovation. “We want to understand better the basic science behind these solar cells, look for ways to develop new technologies based on that understanding, and investigate scalable production methods that could one day bring perovskite solar cells to market.”

    Since they were first developed in 2009, perovskite solar cells have sent quite a jolt through the solar energy world. In just a few years, the efficiency with which lab-scale perovskite cells convert sunlight into electricity has soared. They’re now nearly as efficient as traditional silicon cells, but have the potential to be produced at a fraction of the cost. And perovskites can be easily made into thin films with vivid colors, which raises their potential for use in building-integrated solar cells like shingles, siding, or even windows that can generate electricity.

    “It’s an exciting technology, but there’s still much more work that needs to be done before perovskite solar cells are widely available,” said Padture, who serves as the principal investigator on this new grant.

    For example, scientists lack a complete understanding of exactly how perovskite cells work at the molecular level. Such understanding could help in improving efficiency of perovskite films and optimizing them for different applications.

    It might also be possible, Padture says, to improve efficiency by combining perovskites with other materials and technologies. To explore all those possibilities, Padture’s lab will partner with several faculty researchers, including Kristie Koski of the Department of Chemistry at Brown; Angus Kingon, Domenico Pacifici, and Rashid Zia of the School of Engineering at Brown; Medini Padmanabhan of RIC; and Jinsong Huang, Xia Hong, and Xiao Zeng of UNL.

    Another focus of the project will be looking for ways to scale up the production of perovskite films.

    “The cells that people are making now are quite small,” Padture said. “Small cells are great for testing efficiency in the lab, but the process needs to be scaled up to bring products to market. Better understanding of the underlying materials science is key to addressing this challenge.”

    Padture and his colleague have already made some progress on that front, and they hope to continue with this new grant. Earlier this year, Padture’s lab demonstrated a method for making high-quality perovskite films over relatively large areas at room temperature. Traditional methods for making films involve heat treatment, which can disrupt the film coverage when trying to make large films. The room-temperature method helps eliminate those defects and is more amenable to an assembly-line process.

    “We hope to cultivate industrial partnerships to refine these kinds of techniques and help take this technology to the next level,” Padture said.

    Another issue the researchers will look to address is the fact that the best performing perovskite solar cells contain some lead. The team will look for lead-free perovskite compositions that work equally well.

    The grant also includes a substantial outreach and education effort, which will be led by Karen Haberstroh of Brown’s School of Professional Studies. Students and researchers involved in the project will go to middle and high schools to talk about energy efficiency and green technologies. The project also includes the development of an online college course on solar technologies aimed at people who are interested in entering the green workforce. The grant also provides funding for graduate students and for undergraduate research opportunities.

    The award, which will be paid over four years, was made through the National Science Foundation’s Experimental Program to Stimulate Competitive Research (EPSCoR) program. This latest round of funding went to eight wide-ranging projects totaling $42 million and aimed at fostering research collaborations among investigators and institutions across 12 states.

    See the full article here.

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    Welcome to Brown

    Brown U Robinson Hall
    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.

     
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