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Published on October 27th, 2012 | by James Ayre


New High-Efficiency Quantum Dot Solar Cells Developed

October 27th, 2012 by  

The first solar cell with an external quantum efficiency (EQE) that exceeds 100 percent for photons with energies in the solar range has been created. With these new solar cells, every blue photon that is absorbed can generate up to 30 percent more current than with current technologies.

The external quantum efficiency is the measure of how many photons are converted into electrons within a device.

“While traditional semiconductors only produce one electron from each photon, nanometer-sized crystalline materials such as quantum dots avoid this restriction and are being developed as promising photovoltaic materials,” an AVS news release notes. “An increase in the efficiency comes from quantum dots harvesting energy that would otherwise be lost as heat in conventional semiconductors. The amount of heat loss is reduced and the resulting energy is funneled into creating more electrical current.”

The researchers made use of a process named multiple exciton generation (MEG), so that every blue photon that is absorbed can create at least 30 percent more electric current than other technologies currently allow.

Multiple exciton generation works by “efficiently splitting and using a greater portion of the energy in the higher-energy photons.” Doing this, the researchers were able to create an EQE value of 114 percent for 3.5 eV photons. This proves that the concept can be functional in an actual working device.

Joseph Luther, a senior scientist at NREL, believes MEG technology is going in the right direction. “Since current solar cell technology is still too expensive to completely compete with non-renewable energy sources, this technology employing MEG demonstrates that the way in which scientists and engineers think about converting solar photons to electricity is constantly changing,” Luther said. (Editor’s note: “too expensive” only if you don’t take into account health or environmental costs of fossil fuels; and, not even taking those into account, solar is cost competitive with other energy options in some regions now.)

“There may be a chance to dramatically increase the efficiency of a module, which could result in solar panels that are much cheaper than non-renewable energy sources,” Luther adds.

Source: AVS: Science & Technology of Materials, Interfaces, and Processing
Image Credits: Quantum Dots via Wikimedia Commons

Reposted from Solar Love with full permission.

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About the Author

James Ayre's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy. You can follow his work on Google+.

  • Hmmmm…..okkkkkk, and how much would 25 yrs (the life of a solar panel) of coal cost, for the equivalent amount pf coal to produse the average size home system…use 10,000 watts……about $200 a month in New Jersey…..each panel, including the proportionate amounts for it’s individual install, small components, racking and labor….is about $700…10,000 divided by 240 watts for each panel equals 42 panels or approx $32,500 @ the $3.25 per watt that my company charges…
    When you account for inflation with the price of coal AND the rate increases over 25 yrs…..it’s very doubtful solar would be more expensive, because that’s $60,000 WITHOUT rate increases from coal prices and general business costs from inflation etc., not the cost of the solar system of $32,500 plus maybe an allowance for new inverters @ about 10 to 12 yrs….of $2500…$35,000….from $60,000 leaves $25,000 LESS in cost….PLUS future rate increases……please, put a pencil to things first that’s why everyone isn’t wanting to get renewable energy….propoganda, and / or no real analogy people can see and understand.

  • If this technology allows for large scale manufacture, and if it can be applied to a flexible substrate so it can literally be rolled out as roofing material, this might change the game everywhere.

  • Jigar shah

    This phrase is divorced from reality — Joseph Luther, “Since cur­rent solar cell tech­nol­o­gy is still too expen­sive to com­plete­ly com­pete with non-renewable ener­gy sources, this tech­nol­o­gy employ­ing MEG demon­strates that the way in which sci­en­tists and engi­neers think about con­vert­ing solar pho­tons to elec­tric­i­ty is con­stant­ly changing,” Luther said.

    • Jigar,
      I would take exception to your claim that solar is more expensive than non renewables (coal in this instance). On a watt for watt basis it’s every bit as cheap and considering the “exigent” costs of burning coal it’s infinitely less expensive. Your apparently getting your information from those who profit from the currant energy paradigm who wish to keep things that way.
      Bytheway@Nathan:great quote..

      • Ronald Brak

        Jigar Shah is saying that he disagrees with that phrase. He says it is divorced from reality.

        • Noted and I stand corrected. I misread his post. Thanks for having my back, Ron.

    • C N

      If you calculate the true cost of non renewable resources (war, polution, increased rates of autism most likely due to mercury from coal) there is only one choice.

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