Slashdot is powered by your submissions, so send in your scoop


Forgot your password?
Check out the new SourceForge HTML5 internet speed test! No Flash necessary and runs on all devices. ×
Power Technology

Avalanche Effect Demonstrated In Solar Cells 234

esocid writes "Researchers at TU Delft (Netherlands) and the FOM (Foundation for Fundamental Research on Matter) have found irrefutable proof that the so-called avalanche effect by electrons occurs in specific semiconducting crystals of nanometer dimensions. This physical effect could pave the way for cheap, high-output solar cells. Solar cells currently have relatively low output, typically 15%, and high manufacturing costs. One possible improvement could derive from a new type of solar cell made of semiconducting nanocrystals and could theoretically lead to a maximum output of 44%, with the added benefit of reducing manufacturing costs. In conventional solar cells, one photon can release precisely one electron. However, in some semiconducting nanocrystals, one photon can release two or three electrons, hence the term 'avalanche effect.' This effect was first measured by researchers at the Los Alamos National Laboratories in 2004, and since then the scientific world had raised doubts about the value of these measurements. This current research does in fact demonstrate that the avalanche effect can occur."
This discussion has been archived. No new comments can be posted.

Avalanche Effect Demonstrated In Solar Cells

Comments Filter:
  • APDs (Score:5, Informative)

    by Wilson_6500 ( 896824 ) on Monday May 26, 2008 @11:44PM (#23552063)
    Avalanche photodiodes of certain semiconductor materials have been around for a while now. I believe the novel part of this research is that they're confirming other researchers' data showing that lead selenide semiconductors can exhibit electron cascade effects.
  • Los Alamos (Score:5, Informative)

    by TubeSteak ( 669689 ) on Monday May 26, 2008 @11:45PM (#23552073) Journal

    The avalanche effect was first measured by researchers at the Los Alamos National Laboratories in 2004. Since then, the scientific world has raised doubts about the value of these measurements. Does the avalanche effect really exist or not?
    This is the Los Alamos stuff they're talking about: []

    Solar Cells Get Boost
    Posted by michael on Thursday May 20 2004, @02:15PM
    from the juiced-up dept.
    Science Technology
    An anonymous reader writes "Researchers from Los Alamos National Laboratory have tapped the efficiencies of nanotechnology [] to double solar cells' potential energy production. The key to the method is the use of lead selenium nanocrystals which can produce 2 electrons where 1 was produced before. Other optical applications can also benefit."
  • by Animats ( 122034 ) on Tuesday May 27, 2008 @12:00AM (#23552177) Homepage

    The head of Applied Materials' solar division said in a 2007 talk at Stanford that their current production process costs about 2 years of output for a solar panel. He thinks they can get that down to 6 months of output; he said some things about improvements to the sputtering process. which is derived from IC manufacturing technology where the wafers are smaller.

    They'll probably do it. What Applied Materials does is improve semiconductor process technology. They're the world's largest maker of semiconductor fab equipment. This led them into making LCD displays, and then solar panels.

  • by dakameleon ( 1126377 ) on Tuesday May 27, 2008 @12:39AM (#23552419)

    To me, the big issue is not efficiency but cost per watt.
    Read the bloody summary even!

    could theoretically lead to a maximum output of 44%, with the added benefit of reducing manufacturing costs
    So if the summary is to be believed, you're increasing output nearly threefold, and reducing cost of manufacture. The cost-per-watt ratio moves the right way on both sides.
  • by LynnwoodRooster ( 966895 ) on Tuesday May 27, 2008 @02:03AM (#23552813) Journal
    We seem to cavil about a few million dollars, or even a few hundred million, being spent to jump start emerging energy technology, but we have no problem spending billions on oil industry subsidies.

    Maybe because most alternative energy sources are big money losers? Take a look at page 16 of this report [] for the actual numbers about subsidies...

    I predict once you can start to get alternative energy sources like solar and wind down an order of magnitude or so in terms of cost you'll see things turn around. However, for now they're getting somewhere around 100X the subsidy per Megawatt-hour that "Big Oil" gets.

    An improvement from 15% to 40% simply isn't enough - natural gas and oil get around $0.25 per MWhr, while solar and wind get 100 times that amount per MWhr. And remember, those nasty "Big Oil" companies also pay over $3 in direct federal taxes for every $1 in profit. Over $200 billion flows into the Federal government every year in terms of direct taxes and fees (that's not including the taxes you're paying on consumption of their products).

    Right now, and for the last 20 years, wind and solar have been huge money-losers, and only exists BECAUSE of the massive subsidies. If we subsidized wind or solar at a level to get useful output levels, we'd spend literally trillions more per year.

    And then there's that whole baseload thing...

  • Re:Move along (Score:3, Informative)

    by Ihlosi ( 895663 ) on Tuesday May 27, 2008 @03:56AM (#23553339)
    At least they seem to have moved on from the stupidity that was the "hydrogen economy".

    Oh yeah. There will be a hydrogen economy if/when we manage to get useful energy out of nuclear fusion. Until then, hydrogen is just a fuel with one advantage on paper and a long list of disadvantages in practice.

  • Re:but snowballs... (Score:3, Informative)

    by marcosdumay ( 620877 ) <marcosdumay&gmail,com> on Tuesday May 27, 2008 @07:55AM (#23554699) Homepage Journal

    I am surprised nobody asked that before, but the answer is surprisingly simple. The photons obviously have enough energy do move several electrons, but the photovoltaic cell (junction) is a tiny laywer over some opaque substrate (normaly silicon). So you only have one chance of absorbing those photons.

    There are some manufacturing processes that could create one junction over another, but those processes are very expensive and the material isn't completely transparent. Probably because of this (I don't know about all the problems) people are unable to stack more than 2 junctions.

    So, making a photon displace several electrons at a time seems to be the best alternative. People are doing that with quantum dots for a time now, but quantum dots are very unstable. Now those researches were able to create the same effect using a well designed crystal. That is a big step foward.

  • by hyades1 ( 1149581 ) <> on Tuesday May 27, 2008 @08:10AM (#23554833)

    Your overlook many of the less obvious subsidies. For example, the Army Corps of Engineers routinely dredges canals used by the oil industry at taxpayer expense. The explanation is that they're staying in training. Canals that don't serve oil tankers, regardless of need, do not receive such treatment.

    There are many, many examples of such hidden subsidies, none of which are accounted for in your numbers. I invite you to seek them out for yourself rather than take my word for them.

    An article in Nature 445, 147 (11 January 2007) published online 10 January 2007, and "Money Down the Pipeline: Uncovering the Hidden Subsidies to the Oil Industry" by the Union of Concerned Scientists are good places to start your investigation.

  • by Ioldanach ( 88584 ) on Tuesday May 27, 2008 @08:28AM (#23555017)
    The south facing roof of a 35'x40' house (1400 square feet per floor) with a 7:12 slope is roughly 800 square feet, or about 76 square meters.

    An example of a currently available solar panel [] intended for roofing application is 136 watts, and about 30 would fit on that sample roof, for a total possible 4,080 watts at any given point. Where I am, I can expect an average of 4.5 hours of full production per day, or 18 kwh/day, or 540 kwh/month. That's possible, but would require avoiding high load items like electric cooking, dryers, heating, and cooling. Oh, and the total cost would be $775*30 or $23k, plus installation, charge controller, inverter and storage (batteries).

    A much more efficient solar panel [], not designed to be applied directly to the roof but which would require a frame mounted on the roof and fit in a 7x7 grid, or 49 panels, could generate 9,800 watts max, or 44kwh/day, or 1,323kwh/month. That's a much more useful number, and might even handle an electric dryer, cooktop, and cooling. Still doubt it could handle heating (excepting heat pump or geothermal). And it would cost $53,900, plus installation, charge controller, inverter, and storage. Amortized over 20 years of service, that's $225/month, which is probably cheaper than your electric bill. Though if you had to take a loan, it would cost $414/month for those 20 years, which is probably more than today's electric bill for that amount of power.

    And none of that includes the cost of storage and storage maintenance, which is currently usually battery power.

    Both the cost of the panels and the cost of the storage need to come down for the solution to be viable for the average person.

  • by MrSteve007 ( 1000823 ) on Tuesday May 27, 2008 @11:04AM (#23557337)

    The *fact* is that there are few manufacturers of solar cells.. and most of them are differentiated anyway, so they don't compete.

    That right there should be enough to show that you know next to nothing to what you're talking about. Here's a non-exhaustive list of just the USA's commercial solar panel manufacturers:

    Suniva, GreenBrilliance, Signet Solar, Advent Solar, Innovalight, SunPower, Miasolé, DayStar Technologies, ASE Americas, Inc., Kyocera Solar, Atlantis Energy Inc., EPV Solar, Crystal Systems Energy Conversion Devices, Evergreen Solar, Powerlight, PowerFilm, Silicon Valley Solar (SV Solar), SunWize, TerraSolar, Inc., United Solar Systems Corp. (UniSolar), Solaicx, Alps Technology, OptiSolar, ICP Solar, Day4Energy.

    Some of the larger ones worldwide include Shell Solar, BP Solar, Sharp Solar, and Sunpower. The US based Sunpower Corporation had an annual revenue of over 3/4 of a billion dollars in 2007, and profits of 147 million dollars. Not exactly chump change.

  • by LynnwoodRooster ( 966895 ) on Tuesday May 27, 2008 @12:01PM (#23558165) Journal
    No, we haven't reached the peak of production. Please look at excess capacity [] over the historical record. We've never had a negative amount. Excap is a measure of the unused pumping capacity of oil producers. In the last 5 years, OPEC alone has had at least 1 MILLION barrels a day of excess capacity, on a 60 day window. We're not at the peak of pumping.

    New oil is getting more expensive, but that's because of extraction, not supply. The actual cost of pumping isn't that high, accounting for a few dollars per barrel; the cost is driven by exploration, royalties, transport, and refining. There's plenty of reserves AND pumping capacity - both are actually on the upswing. Peak oil isn't even close in terms of reserves OR pumping.

    Aside: there's one thing the US Congress could do TODAY to eliminate $1 per gallon of gas: simply eliminate Federal taxation of gasoline and the oil companies. That accounts for about $1 per gallon. ""Evil Big Oil" is lucky to make $0.10 per gallon of gas, and they have to pay $3 in taxes for every $1 in profit they make. In the mean time, the Federal government not only gets that $3, but a direct $0.182 per gallon - about double what "Evil Big Oil" makes, per gallon.

  • by An Onerous Coward ( 222037 ) on Tuesday May 27, 2008 @09:12PM (#23565685) Homepage
    You could also have included the next sentence in the article: "But this year, reckons Rune Moesgaard of the Danish Wind Industry Association, wind power will actually save consumers money for the first time, as the benefits resulting from lower power prices outweigh the falling cost of the subsidy."

    Then again, quoting someone named Rune Moesgaard would have made it hard to take you seriously. So I understand.

Perfection is acheived only on the point of collapse. - C. N. Parkinson