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Molecular Stand-in for Solar's Polymer Wires

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  • RemyC
    From: http://www.solaraccess.com/news/story?storyid=7403 Molecular Stand-in for Solar s Polymer Wires NREL-customized system used to make III-V photovoltaic
    Message 1 of 1 , Oct 2, 2004
      From:
      http://www.solaraccess.com/news/story?storyid=7403

      Molecular Stand-in for Solar's Polymer Wires

      NREL-customized system used to make III-V photovoltaic materials; and pulsed
      laser deposition, which is used for depositing a variety of thin films. The
      process is not yet feasible for wire manufacturing, but recent developments
      are promising.

      "Unlike conventional metal wires, polymer nanowires need assistance in order
      to conduct."
      - John Miller, Chemist at Brookhaven Laboratory
      http://www.chemistry.bnl.gov/SciandTech/PRC/miller/miller.html
      (631) 344-4354
      jrmiller@ bnl.gov

      Upton, New York - August 24, 2004 [SolarAccess.com] Silicon has long been
      the catalyst for producing energy from solar photovoltaic (PV) cells, but
      new molecular technology may change all that. Scientists from the U.S.
      Department of Energy's Brookhaven National Laboratory and the University of
      Florida are studying how electric charge is distributed in polymer molecule
      chains, and they have uncovered information that may make it easier for
      molecular wires to replace the silicon conventionally used in components of
      solar PV cells.

      In conventional solar cells, incoming solar energy is transferred to the
      electrons in a semi-conducting material, such as silicon. These electrons
      are guided to an electrode, creating a current that can be drawn off and
      used. Plastic solar technology aims to replace materials like silicon with
      polymer nanowires, which are cheaper and lighter. In plastic solar cells
      constructed to date, electrons must jump from one polymer wire to another in
      order to reach the electrodes. But as the electrons leave one wire in order
      to jump to the next they encounter barriers, and so require larger amounts
      of energy to make the jump. Traversing these barriers uses more of the
      electron's energy than is needed for movement within a silicon base.

      "Long molecules that can act as molecular wires, of which there are many
      variations, are one type of nanoscale object with the potential to lead to
      new technologies, due to their ability to conduct electricity," said
      Brookhaven chemist John Miller. "But unlike conventional metal wires,
      polymer nanowires need assistance in order to conduct."

      Miller and his collaborators want to learn how to eliminate the barriers.
      But first, they must understand elements such as how the electrons move
      within single polymer wires, and the amount of energy the electrons need.
      This information can help developers in the solar industry choose the best
      polymer conductors and design structures for plastic solar cells.

      "Using a cluster of high-energy electrons from an accelerator, we can
      quickly add an extra negative or positive charge to a polymer molecular
      wire," Miller said. "When the end of the wire contains a chemically attached
      'trap' molecule, one where the electrons will be at a lower, more stable
      energy, the charge moves to it. This allows us to 'see' that the wires
      conduct electrons quickly, and over long distances."

      Advances in the solar PV industry rely on creating a product that is easier
      to use, has a greater electrical output per area, and is, most importantly,
      less expensive to manufacture. Fine-tuning the efficiency of electron
      movement in plastic solar technology could help solar gain greater
      competitive advantage in the market.

      Miller and his group plan to look for ways to increase the conduction
      efficiency of the wires. The Office of Basic Energy Sciences within the U.S.
      Department of Energy's Office of Science funded the molecular research. It
      was performed in collaboration with Alison Funston and Norihiko Takeda
      (Brookhaven Lab), and Kirk Schanze and Eric Silverman (University of
      Florida).
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