Steve Mirsky: Welcome to the second episode of our special 2014 Nobel Prize editions of Science Talk, the podcast of Scientific American. I am Steve Mirsky. Today, the physics prize.
Staffan Normark: This year's prize is light.
Steve Mirsky: Royal Swedish Academy of Science's permanent secretary, Staffan Normark.
Staffan Normark: The Royal Swedish Academy of Sciences has decided to award the 2014 Nobel Prize in physics to Professor Isamu Akasaki at Meijo University, Nagoya in Nagoya University, Japan; Professor Hiroshi Amano at Nagoya University, Japan; and Professor Shuji Nakamura at University of California Santa Barbara, for the invention of efficient blue light-emitting diodes, which has enabled bright and energy-saving white light sources.
Professor Per Delsing will now give us a short summary.
Per Delsing: Red and green LEDs have been around for many years, but the blue was really missing. This lamp contains three LEDs: one red, one green, and one blue. If you combine these colors you get white light. This is something that Isaac Newton showed already in 1671. Thanks to the blue LED we can now get white light sources which have very high energy efficiency and very long lifetime. This LED technology is now replacing older technologies. In fact, many of you carry this technology in your pocket. The flashlight and also the screen of modern smartphones uses LED technology.
Professor Olle Inganäs will now continue and give you some of the details.
Olle Inganäs: And we will continue to look at history of lighting, which has been around now for the last few million years of human evolution. We started out by burning fuels inside lamps in a geometry quite similar to that lamp we see over there. However, that has mainly been used here at KVA using incandescent lighting and electrical light over the last hundred years or so, since Edison invented these things. The fluorescent lamp was introduced somewhere in the early 20th century, and then we saw much, much later the arrival of the lighting element that we are now celebrating in this year's Nobel Prize. And what you see is, of course, an enormous increase of the power efficiency of the use of electrical energy in generating light.
Now something like a fourth of our electricity consumption in most industrialized economies goes to elimination. So these effects, having much more light for much less electricity, is really going to have a big impact on our modern civilization. We see that impact. You see it in the streets, you see it on the cars, you see it in the lights. And they're all based on the use of these light-emitting diodes. They come in different colors, not only white, but blue, red, and green, as we saw here, and they have not only the advantage, but much better using the electrical energy. They also give a very much longer lifetime; it may be 100 times longer than that of the standard incandescent lamp that is now being – going in retirement. Also it doesn't bring the mercury along that intermediate generation of fluorescent is contributing as a problem to industrial civilization.
So we will most certainly be able to use this technology. But it took a long while to arrive at this possibility. The red LEDs have been around since the early 1960s, the green LEDs some years later. Advances in semiconductor technology, using this band gap – semiconductors with different band gaps lies at the base of this. But the blue thing – the blue light-emitting diode was very, very difficult to accomplish. Not that there was a lack of effort. There was continuous efforts in industries to generate blue light-emitting diodes. Because today, with the advantage of having these available, we can generate all those colors, we can combine color-mixing with three different colors in the individual lamp, or we can use as you would find mostly maybe on the market today a blue or UV-emitting LED illuminating a thin layer, absorbing this energy, and converting it to other colors.
The structure of these lamps are very similar to what you have at the base of your semiconductor electronics that's driving the information technology diode, a combination of semiconductor materials, where you have one layer carrying holes, one layer carrying electrons. They transport these charges at two different energy levels, but when they meet in this intermediate layer, the active layer, they recombine, and when they fall into each other they turn up and turn light on. So this is the physical mechanism that lies at the heart of this device.
And our laureates of this year have contributed greatly by the inventions that made it possible to grow the gallium nitride and alloys of gallium nitride materials in the particular geometries suitable for building such diodes. You have to be able to grow these, and that was attempted for three decades before the inventions of Akasaki, Amano, and Nakamura. You have to be able to form these diodes, and that was a great problem with preservation of the ______ that's being used to create these. It was solved by discoveries and inventions in these Japanese labs. And you have to introduce more colors and you have to build them into structures which well confine the electrons and the whole searching each other in order to generate light emission. Each layer might be a fraction of a micrometer thin, deposited from the vapor phase in big synthesis machines.
What you see at the market might be a light bulb where the tiny, tiny speck of matter with this structure, sub-millimeter size, is emitting quite a bit of light. And of course the excess to electricity is very weak in many areas of the globe; there is no electricity net, they don’t have electrical power generation accessible. This is changing, because solar lanterns being used to generate light with little electricity help out in balancing the systems where you have solar photovoltaic plants and store them in batteries for use at night. And this is very much in the mind of Arthur Nobel, who wanted to give his prize for the – to the inventions for the better benefit of mankind. And this is why we award this year's prize to Akasaki, Amano, and Nakamura.
Staffan Normark: Thank you, Professor Inganäs.
Steve Mirsky: Per Delsing then spoke with Swedish science journalist Joanna Rose.
Joanna Rose: Per Delsing, you're chair of the Nobel Prize Committee in physics, and this year's prize is awarded for an invention.
Per Delsing: And it's really something that will benefit most people. Artificial lighting is everywhere around us, and this is a way to make artificial lighting much more efficient than other older light sources. It also gets rid of some of the problems that we have with, for instance, fluorescent light sources, which use mercury, and these ones don’t have that, and so we can get rid of the mercury.
But there are also other uses which are maybe not so big today, but maybe in the future we will see portable devices that can disinfect water or to sterilize water, because UV light can kill bacteria.
Joanna Rose: The hardest thing here is that the prize is awarded for invention of a blue light-emitting diode.
Per Delsing: Right. Yeah.
Joanna Rose: So how does it go together?
Per Delsing: Well, it's so that to get white light you really need to combine at least three different colors. So typically you mix red and green and blue. And this is well-known. This is actually known since Isaac Newton in 1671. But it was – so the red and the green LEDs have been around for a long time, but the blue one has really been missing. And so now these laureates have made the inventions that made it possible to make efficient blue LEDs. And so now we have that and we can mix it with the red and the green and that provides white light sources.
Joanna Rose: So what did they do that the others failed to make it?
Per Delsing: Yes, so this is very interesting, because so what's fascinating is that a lot of big companies really tried to do this and they failed. But these guys persisted and they tried and tried again, and eventually they actually succeeded. And you can say there's two major things they did; one was just to grow a sufficiently good material. This is called gallium nitride, and that was very hard to grow and to get a good material, and they managed to do that. And the second part was to dope it in the right. In semiconductors like this you dope both electrons and holes, and it was the hole doping which was very difficult. But they succeeded in doing that too. So it was really an effort where all the three people – contributed to this. Akasaki and Amano worked together in one lab and Nakamura worked in another lab.
Joanna Rose: And they made it in parallel.
Per Delsing: Yes, they very much made it in parallel. And they made different versions of it and they sort of improved each others' results.
Joanna Rose: This seems like a giant step in making light.
Per Delsing: So what's interesting is that this kind of – this way of making light is actually getting quite close to the theoretically possible way, so that every time you put in one electron, you get one particular of light, a photon out. And that's the maximum you can get. And these LED sources are actually going towards that goal. So it will be hard to find something that will be better.
Joanna Rose: So we will be left with this now forever?
Per Delsing: I think so. They will, of course, improve over the years and become a little bit better, but you will not get anything that will be, you know, ten times better. There's not room for that.
Joanna Rose: Mm-hm. So they are now as good as they can be.
Per Delsing: Not quite, but they're over 50-percent efficiency, yeah, and you can only go to 100.
Joanna Rose: And the laureates, they work in Japan? In two different places.
Per Delsing: Yes. So all of the three are born in Japan and they worked in Japan when they did this work. But Nakamura has now moved to California and is in Santa Barbara.
Joanna Rose: How did they react when the telephone call came from Stockholm today?
Pro Delsing: Well, they were of course quite pleased. And Nakamura we woke up in the middle of the night.
Joanna Rose: Because he's in the States?
Pro Delsing: He's in California right now, yes. And Akasaki, he was in – for him it was in evening, so he was, of course, awake. But Amano, he's on an airplane from Japan to France right now, so we didn’t reach him, so hopefully there will be people meeting him at the airport and giving him the good news.
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