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Scientists Develop Solar Cell That Can Also Emit Light 79

An anonymous reader writes: "Scientists at the Nanyang Technological University have developed a solar cell that not only converts sunlight into electricity but also emits light as electricity passes through it. Tuning the composition of the solar cell enables it to emit different wavelengths of light (abstract), and because it is only about 1 micrometer thick, the material is semi-translucent and therefore could potentially be used in windows. The solar cell is comprised of the semiconducting mineral perovskite, which has been studied as a replacement for silicon in solar panels since 2009. Perovskite solar cells are not yet as efficient at energy conversion as silicon solar cells, but gains in this area of development coupled with cheaper manufacturing costs (10-20 cents per watt projected as opposed to 75 cents per watt with silicon solar panels and 50 cents per watt with fossil fuels) make perovskite a popular subject matter in the solar cell industry."
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Scientists Develop Solar Cell That Can Also Emit Light

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  • Heinlein? (Score:4, Interesting)

    by Cpt_Kirks ( 37296 ) on Tuesday March 25, 2014 @04:45PM (#46577499)

    Didn't Heinlein come up with a similar concept? In the story with the moving roads?

  • "Ralos Cell"

  • by kheldan ( 1460303 ) on Tuesday March 25, 2014 @04:46PM (#46577517) Journal
    o Solar cell that also emits light
    o Sandwich it with a perfect mirror
    o Short the leads together
    o Infinite energy!
    • I wish I had points. I also had similar thoughts about some sort of feedback system

  • Infinite energy.


  • Douglas-Martin sunpower screens, which also appeared in "The Roads Must Roll"
  • by jovius ( 974690 )

    A window with tunable coloring.

  • Tuning the composition of the solar cell enables it to emit different wavelengths of light

    Could this be used to make displays? Pros/cons?

  • by Anonymous Coward

    The Solar Powered Flashlight is a reality

  • Yin and Yang (Score:5, Interesting)

    by Dan East ( 318230 ) on Tuesday March 25, 2014 @04:53PM (#46577597) Journal

    Speakers can be used as microphones.
    LEDs can be used to detect light.
    Motors can be used as generators.
    Now some solar cells can emit light.

    Problem is it's matter of efficiency, which is always more of a one way street.

    • Re: (Score:2, Redundant)

      by steelfood ( 895457 )

      Problem is it's matter of the second law of thermodynamics, which is always more of a one way street.

      FTFY. I'm waiting for the yang of that yin to show up. Maybe it won't.

    • Re:Yin and Yang (Score:5, Insightful)

      by Sir Holo ( 531007 ) on Tuesday March 25, 2014 @11:00PM (#46580953)
      Absolutely brilliant comment. Also, you are correct.

      For those who didn't get this post: A transducer is a transducer. It can go either direction, as the physical mechanism is the same, whether one direction or the other. For example, electromagnets move a speaker cone to create sound. Yell at a speaker, and the sound pressure will generate a small voltage (a microphone).

      When poster called it a "one way street," he was referring to the way we engineer and design these transducers. They are optimized, for example to produce sound accurately. This inevitably leads to design trade-offs and optimizations for a particular application. That's all. No one is threatening the second law.

      When land-line phones were wired (not cordless), I discovered as a child that I could yell into the earpiece, which modulated the voltage on the line, and a faint sound could be heard at the other end. The implications for eaves-droppers was that removing the microphone from your phone handset would not render you undetectable to the other people on the line, precisely for the reasons above.
  • by Robert A. Heinlein postulated a solar cell that would emit light []. The story came at it from the opposite direction -- a lighting panel that turned out to also work as a photovoltaic cell. Heinlein's story was published in 1940. Only took 3/4 of a century for engineering to catch up with science fiction.
    • by OzPeter ( 195038 )

      by Robert A. Heinlein . Only took 3/4 of a century for engineering to catch up with science fiction.

      So where is the gratuitous sex between the Researcher and his mother? It can't be a Heinlein rip off unless there is gratuitous sex somewhere.

      • by Robert A. Heinlein . Only took 3/4 of a century for engineering to catch up with science fiction.

        So where is the gratuitous sex between the Researcher and his mother? It can't be a Heinlein rip off unless there is gratuitous sex somewhere.

        I don't think ALL of Heinlein books had gratuitous sex scenes I don't remember one in Sixth Column for example but it has been a while since I read it so I may be mistaken.

  • by qparadox ( 1105733 ) on Tuesday March 25, 2014 @04:59PM (#46577665)
    When the article references perovskites, it is referring to a crystalline structure similar to the mineral perovskite (calcium titanate). These solar cells are NOT made of calcium titanate, nor is calcium or titanium even in them. Instead, they are make of organic - inorganic halides, in this case: CH3NH3PbX3 (where X = Cl, Br, I). The proper wikipedia link for the summary is: []
    • I'm actually curious where you got the information from. The linked articles from Wikipedia don't mention specific materials, with the exception of one. That material is specifically C.H3.N.H3.Pb.I.Cl2 (starting from C.H3.N.H3.I and Pb.Cl2), which falls within your broader categorization.

      <offtopic>Why is Slashdot using a font where it is easy to confuse I and l?</offtopic>

  • by Anonymous Coward on Tuesday March 25, 2014 @05:03PM (#46577707)

    Any solar cell will emit light ... if you run enough current through it.

  • I remember the Heinlein story - it's been many years, I'll have to dust off that old book and read it again - but I also recall that regular LED's have always done this too, but just very poorly on the light to electricity conversion part. Seems I remember a project long ago taking advantage of this - something from Forrest Mims maybe?
    • by Anonymous Coward

      something from Forrest Mims maybe?

      Is that the "box of chocolate" guy? He seems to have been everywhere.

  • Maybe the equipment needed to generate electricity from fossil fuels costs 50 cents per watt, but then you also need to buy the fossil fuels. I would expect the cost of fossil fuels would be measured in cents per Joule. If solar cells can produce electricity for 10 cents per watt with no fuel costs, I think we should work on scaling this up as fast as we can. We can all have more energy for less money than ever before! Of course, we also need to work on how to store energy produced on sunny days for use dur
    • I agree this is the wrong unit since fuel costs are the main thing (plus environmental and public health costs) but someone may have tried to make things inter-comparable by integrating over twenty years of solar panel use, found the equivalent fossil fuel cost and divided back down. Looks like they may have forgotten to make electricity from the fossil fuels (neglected efficiency) since grid parity comes in at around $1/Watt for solar.
  • It's transparent solar panels on top of transparent solar panels.

    It's transparent solar panels all the way down...

  • Can someone who understands the subject matter better than I do please explain to me how "cents per watt" is an applicable comparative metric for fossil fuels and solar cells?

    It would (at least apparently) seem to me that when you use a unit of fossil fuel, it is gone. By contrast, if you have a solar cell, it will continue to be useful for as long as the sun and the cell have line of sight.

    So aren't fossil fuels inherently measured in Joules?

    • by geekoid ( 135745 )

      when talking about solar, money per watt is usually the cost of the cell divided by the watt output.

      So a 200 watt solar panel* that cost 100 dollars would be 50 cents a watt.

      *yes I just changed it form cell to panel.

    • Re:Cents per Watt (Score:5, Informative)

      by Maury Markowitz ( 452832 ) on Tuesday March 25, 2014 @08:44PM (#46579811) Homepage

      > Can someone who understands the subject matter better than I do please explain
      > to me how "cents per watt" is an applicable comparative metric for fossil fuels and solar cells

      The price of electricity is basically the total money you put into running the plant over its lifetime divided by the total amount of power you get out of it during that lifetime. That's called the "levelized cost of electricity" or LCoE.

      For plants that don't use fuel - wind, hydro, PV - the total amount of money is basically the price of the plant, the price of repairs and operations, and the price of borrowing the money to pay for the first two. For systems that go up in a short time, like wind and PV, the costs are utterly dominated by the price of the equipment.

      For other sources the total cost of operations varies. Nuclear plants use fuel, but so little of it that it's not a major factor. However, these plants have enormous up front costs and decades long building cycles, so their LCoE tends to be utterly dominated by the prevailing interest rate. Coal and natural gas plants cost about 1/4 that of a nuclear plant and are therefore more heavily dominated by fuel costs, so their cost of operations goes up and down with the cost of the fuel.

      So when you're trying to compare the price of a PV plant to a coal plant, for instance, the key metric in the case of PV is the cost of the panels. That's because there's no fuel cost and almost zero maintenance (had mine 5 years, done exactly $0 work on them so far).

      Since the amount of sunlight shining in a particular area is averaged over long periods and available online, you can then predict the amount of power the plant will produce over its lifetime. For instance, in Toronto 1000 W worth of panels (i.e., a set of panels that will produce 1000 watts under specific conditions) will produce about 1200 kWh of power every year, after all conversion losses are factored in. We expect those panels to last about 25 years. So then

      LCoE = (cost in cents/watt * size of system in watts) / (25 years * 1200 kWh * system size in KILOwatts)

      So let's say the system, *all in*, costs you $3.50 a watt (about right these days). Then if you put up a system with 12 panels like mine, you get

      LCoE = (3.50 * 3000) / (25 * 1200 * 3) = 11.66 cents/kWh

      I think you'll find that is very comparable to what you are paying from your local utility, which is why PV is the fastest growing power source in the world today.

      This same basic formula can be used with any power source, but the inputs will differ. For instance, the equivalent number for a nuclear power plant is about 7500 to 8000 kWh per kW of panels installed, because they run full out 24/7, or at apt 85% full power, or "capacity factor". But as you might expect, construction costs are much higher, about $8/W or more (that plant in Florida came in at about $11/W, which is why they cancelled it).

      Likewise, wind turbines here in Ontario average about 30% "capacity factor" (CF), so that's about 2600 kWh/kW. That sounds bad until you consider they cost about $2/W installed. So when you compare the two head up it's something like (2 / 0.3) = 6.66 for wind vs. (8 / 0.85) = 9.41 for nuclear, which is why wind is the second fastest growing power source on the planet.

      And that's why we measure everything in terms of cents per watt. If you know that (although dollars per watt is the typical figure) and the capacity factor, everything else sort of disappears. So you can get a *very* good idea of the economics simply by dividing the ($/W) by (CF).

      If you'd like to do this on your own, with real numbers and more factors, you can. It's actually very easy and you can run through a given location in about 2 minutes:

    • It's probably the energy cost to make 1 watt of solar panel.
      Assuming the summary is correct it costs 75 cents of power to make 1 watt of solar panel if you use solar panels to deliver that power and 50 cents of power if you use fossil fuels.
      The reason for the cost/kwh is properly explained by sibling posters.

  • by SimonInOz ( 579741 ) on Tuesday March 25, 2014 @06:27PM (#46578549)

    So we could have a torch (sorry, flashlight) that only works in sunlight ... ? I'm not sure I'd buy one of those.

    • There is a magic trick for that: a small battery to store the gathered energy for night time use.
      Besides, it'll be perfect for windows. Tinted windows by day and light emitting panels by night.

  • by Anonymous Coward

    Solar panels are fundamentally identical to LEDs, just optimized to absorb light instead of emit it. Forward-biasing a solar panel and measuring its light emissions is a common method of inspecting the panel for damage. Perhaps they managed to get this particular solar cell technology to emit visible light for the first time? Silicon solar cells generally only emit infrared light, but it's pretty easy to get a gallium arsenide cell to glow red without damaging it.

  • by Animats ( 122034 ) on Tuesday March 25, 2014 @07:10PM (#46579023) Homepage

    Another one of those "nanomaterial" stories. Claims of "cheaper manufacturing costs" for a product not yet produced in volume. Yet another "solar cell made with printing technology" scheme. Sigh.

    So this thing is one micrometer thick and they want to print it on windows. How long does it last, hammered by UV and weather and thermal cycling? Lifetimes for silicon solar panels are now up to 25 years (warranties are available for that long), and there's falloff in output over that time. Can a 1 micrometer film match that? Realistically, it's going to have to be behind a protective layer. Maybe it could be on the surface of the middle layer in double-pane glass, but now you have a complex sandwich to manufacture. There goes the "cheap manufacturing".

    Vertical windows are poorly oriented for capturing power. Solar shingles [] are better oriented. (Also, they exist, and you can buy them now.) And, as the head of Applied Material Solar pointed out a decade ago, half the cost is installing the thing. These guys need better numbers to back up their cost claims.

    • Vertical windows are poorly oriented for capturing power.

      While true, I believe the concept is more for skyscrapers/tall building where there is far more surface area down the sides on the building than on the top. So even if it is less efficient, you've got the space and it might as well be used for generating electricity.

      No, I'm not going to take the solar panels off of my roof and just get fancy solar-energy generating windows. But if I was building a 20-story skyscraper, I might consider doing this. Assuming, of course, that your other valid concerns are ad

    • "Vertical windows are poorly oriented for capturing power."

      In the winter a south-facing vertical window does pretty well with the winter sun being rather low in the sky if you are 40 degrees or more of latitude.

    • Solar shingles are better oriented. (Also, they exist, and you can buy them now.)

      These things seem a hell to install. So many separate panels means so many separate cables.
      And the heat buildup! Directly placed on the isolation is a bad idea. air needs to flow behind solar panels to keep them cool. A raised panel creates a chimney effect behind it, cooling quite efficient.
      On a hot day in a reasonably warm climate (the Netherlands) roof tiles of 80ÂC (180F) aren't strange.
      Normal shingles can handle temperatures of far over 100ÂC. (I have no data on how much exactly, but boiling

  • If you reverse the voltage enough on a Gallium Indium Arsenide solar cell it will glow red just like a diffuse light emitting diode. You have to remove the protection diode from the cell for that to work however.

  • Pfft (Score:5, Funny)

    by Hamsterdan ( 815291 ) on Tuesday March 25, 2014 @07:45PM (#46579369)

    That's nothing, while learning electronics as a kid, I invented a way to turn LEDs into Smoke Emitting Diodes...

  • Does this mean these cells could be installed over farmland/ in greenhouses so we could get double use out of the same land? I kinda like this idea.
    • > Does this mean these cells could be installed over farmland/ in greenhouses

      You mean like this?

In the realm of scientific observation, luck is granted only to those who are prepared. - Louis Pasteur