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  • richardmitnick 1:50 pm on August 19, 2013 Permalink | Reply
    Tags: , , , , , Solar Power   

    From Brookhaven Lab: “Polymer Solar Cells Employing Förster Resonance Energy Transfer” 

    Brookhaven Lab

    August 19, 2013
    No Writer Credit

    What is the Scientific Achievement?

    Two crucial tasks exist for realizing high-efficiency polymer solar cells: increasing the range of the spectral absorption of light and efficiently harvesting photo-generated excitons. In this work, Förster resonance energy transfer (FRET)-based heterojunction polymer solar cells that incorporate squaraine dye (SQ) were fabricated and investigated. The high absorbance of squaraine in the near-infrared region broadens the spectral absorption of the solar cells and assists in developing an ordered nano-morphology for enhanced charge transport. Femtosecond spectroscopic studies revealed highly efficient (up to 96%) excitation energy transfer from poly(3-hexylthiophene), also known as P3HT, to squaraine occurring on a picosecond timescale. A 38% increase in power conversion efficiency was realized to reach 4.5%; this finding suggests that this system has improved exciton migration over long distances. This architecture transcends traditional multiblend systems, allowing multiple donor materials with separate spectral responses to work synergistically, thereby enabling an improvement in light absorption and conversion. This discovery opens up a new avenue for the development of high-efficiency polymer solar cells.

    cells
    Next generation solar panels could yield substantially lower costs per kilowatt-hour with this technological development.

    Why Does This Matter?

    A new energy transfer mechanism has been exploited for the first time, allowing significantly more efficient energy harvesting in P3HT/dye solar cells compared to P3HT-alone solar cells. Also, broadening the light absorption spectrum into the near-infrared region and developing nanoscale parts to the solar cell has improved the device.

    graph
    Energy level diagram of the components of the ternary blend solar cell highlighting pathways for charge generation.

    Allowing different light-absorbing materials to work synergistically has led to well-ordered polymer networks without post-processing.”

    See the full article here.

    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. 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.
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  • richardmitnick 12:44 pm on August 5, 2013 Permalink | Reply
    Tags: , , , , , Solar Power,   

    From Stanford: “Disorder can improve the performance of plastic solar cells, Stanford scientists say” 

    Stanford University Name
    Stanford University

    Instead of mimicking rigid solar cells made of silicon crystals, scientists should embrace the inherently disordered nature of plastic polymers, a Stanford study has found

    August 4, 2013
    Mark Shwartz

    “Scientists have spent decades trying to build flexible plastic solar cells efficient enough to compete with conventional cells made of silicon. To boost performance, research groups have tried creating new plastic materials that enhance the flow of electricity through the solar cell. Several groups expected to achieve good results by redesigning pliant polymers of plastic into orderly, silicon-like crystals, but the flow of electricity did not improve.

    Recently, scientists discovered that disorder at the molecular level actually improves the polymers’ performance. Now Stanford University researchers have an explanation for this surprising result. Their findings, published in the Aug. 4 online edition of the journal Nature Materials, could speed up the development of low-cost, commercially available plastic solar cells.

    cell
    These X-ray images reveal the microscopic structure of two semiconducting plastic polymers. The bottom image, with several big crystals stacked in a row, is from a highly ordered polymer sample. The top image shows a disordered polymer with numerous tiny crystals that are barely discernible.

    ‘People used to think that if you made the polymers more like silicon they would perform better,’ said study co-author Alberto Salleo, an associate professor of materials science and engineering at Stanford. ‘But we found that polymers don’t naturally form nice, well-ordered crystals. They form small, disordered ones, and that’s perfectly fine.’

    Instead of trying to mimic the rigid structure of silicon, Salleo and his colleagues recommend that scientists learn to cope with the inherently disordered nature of plastics.”

    X-ray analysis

    To observe the disordered materials at the microscopic level, the Stanford team took samples to the SLAC National Accelerator Laboratory for X-ray analysis. The X-rays revealed a molecular structure resembling a fingerprint gone awry. Some polymers looked like amorphous strands of spaghetti, while others formed tiny crystals just a few molecules long.

    ‘The crystals were so small and disordered you could barely infer their presence from X-rays,’ Salleo said. ‘In fact, scientists had assumed they weren’t there.’

    By analyzing light emissions from electricity flowing through the samples, the Stanford team determined that numerous small crystals were scattered throughout the material and connected by long polymer chains, like beads in a necklace. The small size of the crystals was a crucial factor in improving overall performance, Salleo said.

    Other authors of the study are postdoctoral scholar Koen Vandewal of Stanford; Felix Koch and Paul Smith of ETH Zurich; Natalie Stingelin of Imperial College London; and Michael Toney of the SLAC Stanford Synchrotron Radiation Lightsource.”

    See the full article here.

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

    Stanford University Seal


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  • richardmitnick 11:28 am on May 21, 2013 Permalink | Reply
    Tags: , , Solar Power   

    From Brookhaven Lab: “Soaking Up Sun at the Long Island Solar Farm for Energy Research at Brookhaven Lab” 

    Brookhaven Lab

    May 16, 2013
    Pat Looney

    “Bring on the sunshine! April showers are behind us and the sun is shining a little longer each day in the northern hemisphere. That means the 200-acre Long Island Solar Farm (LISF) at Brookhaven Lab is producing increasing amounts of renewable energy for Long Islanders and data for our researchers.

    farm
    The 200-acre Long Island Solar Farm (LISF) is located at the east end of Brookhaven Lab. By hosting the LISF and future Northeast Solar Energy Research Center on site, Brookhaven Lab has positioned itself at the forefront of new research to help develop real-world solar energy technologies.

    The LISF is the largest solar array in the eastern U.S. and is located at the east end of the Lab site. It contains 164,312 photovoltaic panels grouped and mounted onto more than 6,800 racks. The LISF can produce peak power output of 32 megawatts (MW) of alternating current that powers homes and businesses. Operations began in November 2011, and during its first 12 months, the LISF produced a total of about 54,000 megawatt-hours (MWH) of energy. That’s 23 percent more than the design estimates for 44,000 MWH, which is equivalent to the power usage for about 4,500 homes.

    LISF, LLC—a joint venture between BP Solar and Met Life—owns the array and LIPA purchases the electrical output, distributes it, and sells it to customers. BP Solar has announced its intention to exit the solar energy business and we expect it to sell its share to another party, but this would not affect operations or agreements with Brookhaven and the U.S. Department of Energy (DOE). While the Laboratory doesn’t get any electricity from the LISF, it does get large amounts of data from operations. The Lab will get both electricity and research data from the Northeast Solar Energy Research Center (NSERC) being developed on site. By hosting both arrays here, the Lab has positioned itself at the forefront of new research to help develop real-world solar energy technologies.”

    See the full and very enlightening article here.

    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. 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.
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