Gallery: Researchers Create First Solar Cells With Quantum Efficiency o...


This morning saw a solar breakthrough at the National Renewable Energy Laboratory (NREL), where researchers created a quantum dot solar device that has a higher energized particle percentage output than its energized particle input. The photocurrent of a solar device — photocurrent shows the efficiency of a solar cell — is expressed as a percentage and is found by measuring the number of electrons flowing per second out of the solar cell divided by the number of photons per second of an energy entering the solar cell. NREL researchers have developed a solar cell that has a photocurrent of 114%, which is the most efficient ratio ever seen before.

The key to these über efficient solar devices is Multiple Exiton Generation (MEG). This process says that if a solar cell absorbs a photon that has enough energy needed, that one photon entering the solar cell can produce more than one electron-hole pair exiting the solar cell (the electron-hole pair is the unit of energy generated by the solar panel that translates into energy transmitted by the device). Researchers believe this discovery could significantly increase the efficiency and cost effectiveness of solar power over fossil fuel power.

The cell used to achieve the photocurrent of 114 was a layered cell which consisted of antireflection-coated glass, a transparent conductor, a nanostructured zinc oxide layer, a quantum dot layer and a thin layer of gold on top. In addition to being highly efficient — we might even say overefficient — at translating energy in to energy out, the quantum dot solar cell in question was also highly efficient at absorbing solar energy as well. Many current solar cells only absorb a small amount of the photos that come in contact with them and therefore aren’t able to convert all of the sunlight that runs across their surface into electricity. This new solar cell was extremely efficient when it came to absorption. That coupled with the high photocurrent and a relatively low production cost could make this discovery a key to bringing solar energy’s cost down below that of nuclear energy and perhaps even the cheapest and dirtiest of them all, coal.

Via Engadget


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  1. John Kang October 31, 2012 at 11:34 pm

    Nononono…the 114% efficiency is not really 114% efficiency. The problem with current photocells is a) very \\\”picky\\\” about photons. Many photons are simply wasted or reflected as they do not meet the cut-off frequency. b) whilst it is theoretically possible to energize multiple electrons with a single wave packet of energy, so far it is a very complex-quantum mechanics, nuff said- with drastic reduction in max kinetic energy per electron. What the above achieved was based on a system where number of electrons divided by number of photons. Since there are much more photons with excess energy over energy required to release an electron, this is not a true efficiency.

    TL;DR, efficiency above is NOT Pin/Pout, and is not a true efficiency in terms of pure energy.
    Still, it is very impressive.

  2. phoenix168 December 23, 2011 at 8:54 pm

    @freealex1 maybe we have the laws wrong. Since recorded history we believe that we have “worked Out” the inner workings of the world around us and established “Laws” to explain them. We continue to compartmentalise what we don’t understand and design tests to disprove them. It’s not that it isn’t there, we don’t know how to find it.(Black Holes?… not so long ago).
    Lets hope it is 114%, long may new discoveries continue.
    Yeah Science!

  3. Ekstan38 December 21, 2011 at 4:34 am

    The important is where can we get these great solar cell from? How much it’s cost?

  4. eddietan December 21, 2011 at 4:30 am

    If the new solar cells can really maximized the absorption of generating more energy than the current solar cells. Of course it’s great news for the communities. But how much the cost will be?

  5. Freealex1 December 20, 2011 at 7:10 am

    Sorry, can you clarify what has actually been achieved? Are you saying that they’ve somehow managed to ‘violate’ the law of energy conservation (i.e. – that they are taking in 1.00 Watt of sunlight, and getting 1.14 Watts of electricity out)? That seems rather doubtful…

  6. Egalitare December 19, 2011 at 4:49 pm

    When they run this a few dozen more times and revise down to “just” 75%, it will still be mindbogglingly impressive.

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