Re-light my diode: Trio of boffins scoop physics Nobel for BLUE LEDs The 2014 Nobel Prize for Physics has been awarded to three researchers for coming up with the blue LED - allowing humanity to break free of the red and green prison it had languished in until then. Isamu Akasaki, Hiroshi Amano and Shuji Nakamura have been honoured “for the invention of efficient blue light-emitting diodes …
I'd like to know what their method was. If they sat and worked out what was needed then built it I'm impressed with their genius. If they sat trying thousands of different chemicals until one shone blue then I'm not convinced that a Physics Nobel is appropriate despite the obvious advantages of the technology. I'm not saying no Nobel at all, or no prize or reward, just not the physics one - the benefit to mankind is clear and they should certainly be paid for their work.
It wasn't a case of just mixing chemicals and hey presto blue light. There was some bloody clever physics behind hit making it work.
However even if they spent 20 years alone, when multi-billion pound companies failed, just mixing hundreds of chemical together until it worked, why on earth does that not deserve a nobel prize; if any thing the more effort you put into it, the more you deserve in return.
Did Edison just go, hmm bit of wire, bit of electric, hey presto light? No he spent a long time trying out different methods.
Did Marie Curie, just go oh look what's this funny metal, I'll call it Plutomium. No.
In fact I'd be annoyed if they just did go, ok this compound emits blue light, Nobel prize please.
I think you conflated polonium and radium there.
You're right though, and the blue LED is as revolutionary in its way as the original Swan/Edison lightbulb. The incandescent bulb made modern cities possible - imagine the Shard lit by gas. The blue LED means that nearly a quarter of current electricity consumption can eventually be eliminated. In effect, building an LED lamp plant could avoid the need to build an entire new power station.
The implications for the developing world are just as great. Low power lighting in the tropics makes education possible - without it every activity that needs good light must be fitted into 12 hours. With it, people can work in the day and learn in the evening.
I can't help thinking they got the wrong prize; given the potential benefits, a joint award of the Peace Prize and the Economics prize might have been more appropriate.
I love LED lamps, but:
1. How can these Swedes be so sure that "the 21st century will be lit by LED lamps"?
2. LED lamps have begun to replace other lamps MAINLY because the low-energy fluorescent lamps that were forced upon us over the past few years are so crap, and because the simple, straight-forward and cheap filament bulbs are gradually being banned by Western governments. The cost/benefit analysis for most people, who think short-term, will be negative.
The onset of LED lamps is not a 'revolution'. Most applications could have been covered by existing technology. This is merely a useful and beneficial incremental improvement in the struggle to cut energy use.
Point 1 - EU survey shows already ~43% of Swedes buy only LED bulbs, so reckon that statement is just reflecting the trend they are seeing.
Point 2 - In order to stimulate R&D and maintain a commercial lead, Chinese government subsidies for LED fabs (majority of world LED fabs are in China) are dependant on lowering costs of LEDs - the details are a bit fuzzy as I haven't had anything to do with it for a year or so, but essentially I think the goal is cost parity with existing technologies by 2020. This is currently on track, thus negating the short term vs long term argument.
That's the kind of thinking that causes people in country districts to buy second hand 4x4s because they are remarkably cheap, then discover how much they cost to run.
Filament bulbs are far from cheap if life costs are taken into account. If we had not had CFLs, the pressure to get in LED bulbs would be several times more intense - because the amount of electricity generation going to lighting would be much higher, and because long tube fluorescents are not accepted by the public outside kitchens.
That's the kind of thinking that causes people in country districts to buy second hand 4x4s because they are remarkably cheap, then discover how much they cost to run.
That's what I said to a bloke who had a 5 litre V8 muscle car.
His reply "BMW £28,000: this: £8,000. £20,000 buys a LOT of fuel..."
His reply "BMW £28,000: this: £8,000. £20,000 buys a LOT of fuel..."
Because the BMW and the muscle car are equivalent, price aside.
Mind you, I wouldn't buy the BMW just because of their horrible infotainment control system. But it's false economics nonetheless.
(Why not buy no car at all, and walk everywhere? £28,000 buys a lot of food and shoes.)
Indeed. Now mineral LEDS have a problem. They are a point source.
I have seen a MUCH broader area emit light with some organic light emitting polymers, that made them highly suitable (if they could have been stabilised) for a diffuse light source.
Sadly that company was chasing the wrong dream - organic LED panels - and went bust.
But I thunk the final answer to lighting may in fact be something more along those lines - a combination EV/fluorescent emitter coating a glass envelope, but NOT excited by a mercury plasma.
Not that I dont think LEDS are cracking good technology, but I think there may be cheaper ways.
"Did Edison just go, hmm bit of wire, bit of electric, hey presto light? No he spent a long time trying out different methods."
Maybe not, but Edison wan't a physicyst either. As someone else said, another Nobel prize would have been appropriate for the outcome, but the physics of LEDs is well known already so this wouldn't appear to be much of a breakthrough in that field.
The physics behind it has been around for decades, they were invented in the 80's remember. However the innovation, and hence why they win an award, is that they made it a commercially viable product. Silicon manufacture isn't simply a case of saying "here's a wafer of silicon, now make me an LED". There's a lot more to it than that. I used to work in optoelectronics as a production engineer and there were so many factors that affected whether the silicon was actually any good for optics, one being the age of the caesium cyanide they were using in the waferfab, but also how well the silicon had actually been grown. Just 1% rotation in the crystal alignment and when you tried etching it they left grooves in the etched channels causing the optical fibre to sit above the silicon (so any light being emitted from the silicon was hitting air instead of the end of the fibre.
The physics of lasers is well-known too.
But so far noone's managed to produce a green semiconductor one (current green lasers are infrared lasers with output passed through a doubling crystal)
What's more remarkable than the prize is the fact that Nakamura was ordered to cease his research into blue leds as he wasn't making progress and his employers didn't see a market. He was so determined to create the device that he continued on his own time and expense, which has made him a very, _very_ wealthy man.
"He nicked the idea from Joseph Swan......."
Yes, but he did spend quite a number of years making it last more than 2-3 hours.
His adventures stealing the Lumiere Brothers' invention and output essentially created Hollywood - the filmmakers of the time were trying to get as far away from Edison and his control-freakery as possible.
@AC
Even if it was the combination of endless substances at random, so what? What of Penzias and Wilson, who won the same medal for, essentially, stumbling on the microwave background radiation. They weren't the first to do so but simply had the good fortune of noticing it at a time when a group of physicists had proposed it and were beginning to search for it.
Had Peebles, Dicke and Wilkinson not been doing their research at the same time. then Penzias and Wilson likely would have simply got on with their own research like others before them. The only real difference was that when they went looking for an answer, there was one ready*.
At any rate, the development of the blue LED wasn't just random combination, though there were lots of experiments, obviously. I believe this prize is thoroughly deserved. If you're not aware, blue LEDs were an essential stepping-stone to white LEDs, which are essentially filtered blue LEDs.
* - Not to say that they weren't thorough because they were, but given they had their own jobs and research, it's very unlikely they would have developed the same answer independently - especially as they were (I believe) proponents of the Steady State theory.
@Allan George Dyer
My mistake, already corrected (before I saw your comment). For those wondering what Allan is talking about, I accidentally wrote that blue LEDs paved the way for yellow LEDs, which is clearly ridiculous.
What they did was pave the way for white LEDs, and this was done, more-or-less, through a yellow coating, which works to not only produce white but, as the eye is more sensitive to yellow than blue, increase the apparent brightness.
white LEDs, which are essentially filtered blue LEDs
Well, they're not going to be *filtered* blue LEDs, as the white-spectrum requirement just isn't there.
According to the interview[1] on the news this morning, white LEDs are actually a blue LED inside a white phosphor. I suspect, therefore, that other colours of LEDs could also be used to make white LEDs, albeit not necessarily with the same efficiency.
Vic.
[1] The interview was on the BBC, and it was with one of the Japanese guys who won the prize, so I reckon he was probably telling the truth.
as far as I can remember the trick is to fnd a substance with the right band gap to emit the color light you want.
Presumably gallium nitride fits that bill.
THEN the problem is to make something that emits light and lasts more than a nanosecond.
THAT was probably the real challenge.
good article in wiki
http://en.wikipedia.org/wiki/Gallium_nitride
The use of frozen carbon-dioxide to make clouds form rain was discovered independently by two different men. One used a careful theoretical analysis of the properties needed and determined that CO2 snow would meet them. The other got a humidity chamber and shovelled chemicals in it one at a time until it worked.
In my mind, both had perfectly valid techniques because both got the right answer*. Oh, and Edison, after trying and failing 10,000 times to produce a cost-effective light bulb filament, said "I have not failed. I've just found 10,000 ways that won't work." That 10,001st try was the charm.
* - quite unlike climate modelling, which has produced consistenly wrong results for thirty years+.
+ - global warming was being hawked to gullible insurance executives by the "Commission for the Future" in the early years of the Hawke government.
to be fair, he probably also said we'd be flying around in atomic powered cars
Here is a (bloody huge) actual photo of an actual atomic powered car. Admittedly you can't just hop in and drive it, on the other hand we did fly it to another frikkin' planet which some might argue is even more impressive.
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Urban legend from a certain industrial R&D lab. They did some very early liquid crystal work under government funding. You can picture it. 1ft square plates of glass accurately ground, in a jig with spacers. The cynics "when you can make that the size it'll fit on someone's wrist, I'll be useful - ha, ha."
It may be world-changing (and cynically the environmental stuff could be a factor these days) but what revolutionary work in physics was involved here? That's a real question not being sarcastic - the real-life implications are big but is it really a change to how we understand physics?
Anyone up for a concise, understandable explanation for the educated layman?
The real physics is getting an atom to emit a blue photon...
Since creating a blue photon needs more energy than a red or a green one, it's a bit hard to convince an atom to emit one because atoms are a bit lazy and like to return to the lowest energy state possible as soon as they get the chance.
The trick basically lies in storing enough energy in one atom and then transferring it to another so that the second atom gets 'pumped up' to a high enough energy state to emit blue light...
Caveat - I've not found out what they actually did - physics-wise.
But, it's not an individual atom emitting - this is solid state physics. There's some clever stuff with making structures that change band gaps by being sized at the quantum wavelength scale in 1, 2 or 3 dimensions. I.e. quantum well, ... quantum dot technologies.
What these guys did - dunno - need more info. Did they really come up with the underlying physics and take it through to a workable device ? Not normally the same teams doing both.
Before launching into the Physics, how can I upvote the strapline?
How many .. to change a light bulb, I LOVE it.
As is mentioned above, blue light needs more energy per photon. GaAs was used for red LEDs originally, and alloying it with Indium and Gallium in various ratios causes the bandgap of teh material to increase and therefore we can reach yellow then yellow/green, and these days, pure green - of the sort one can hold in one's own mortal hand.
For Blue we need to find a material with more bandgap than GaAs, InGaAs, InGaAsP, InGaAlAsP and all that lot - you can see that the choice of material variants has grown, testament to the work that has been put into this market.
GaN and SiC are both contenders, early blue LEDs used SiC but the brightness is limited, it is an indirect band-gap material - a phonon is needed to carry away some excess momentum when the photon is emitted, reducing the probability of emission and wasting some energy.
Both SiC and GaN are exceedingly hard to grow in pure form, being riddled with screw dislocations, threading dislocations, foreign atom inclusions and many more nastys. GaN is the worst, we need defects per cm2 of a few hundred, typical bulk materials have 10^6 to 10^9.
To solve this we need to grow thin layers on a substrate that we can make decent crystals of, like sapphire (Al2O3) or SiC or even GaAs. The substrate order will force the thin layer to be defect-free. Unfortunately all the substrates have a different lattice constant, the mismatch needs to be accommodated somehow through interposing layers.
It is in this area where the Nobel Laureates excelled, Akasaki and Amano used sapphire with a buffer layer of AlN, whilst Nakamura found a way to grow GaN starting at low temperature then increasing the deposition temperature, spreading the strain across some distance.
It is all to do with the temperatures and gas compositions, including different dopants - and finally the sequencing to build crystalline thin layers that can cool down from the forming temperature (800-1400'C) to room temperature without shattering.
Since then there have been many more developments, like quantum dots, plasmonic resonators - and all sorts of means to get the light out of the crystal, but these are not part of the prize-winning research.
>>The real physics is getting an atom to emit a blue photon...
That part I know, jumps between energy levels. It doesn't sound terribly revolutionary, more like trial and error. I wondered if some new understanding in physics allowed them to figure out how to do it, or if it's more a case of a long hard slog than a new discovery?
edit: hadn't seen the post above. So "long hard slog" is accurate but I don't mean that as a criticism.
I love our new LED light emitting overlords, and indeed my entire house is now filament and flourescent free (I might have missed the fridge light) but the one thing I can confidently say it won't do is reduce energy consumption. There will just simply be more lights (and light pollution), and more TV displays (I have 5 if you include computers, not counting laptops)
There will just be more people with hideous Christmas light decorations on their front garden, and they'll run from October to March.
I can confidently say it won't do is reduce energy consumption
Really? LEDs use about 5% the power of indandescents. So you would need to light 20 rooms in your house with LEDs to balance out one room with incandescents, or light the whole house 20 times brighter.
While you use more energy in other places, for example display equipment, the cut in energy usage for lighting is hardly incremental - it's revolutionary. While lighting a whole house 20 years ago used maybe 2 or 3 kW, now it is more like 100-150 Watts. That is a phenominal difference.
All other technologies used for street lights either cannot be switched on instantaneously and/or their life is reduced by every switching cycle. So as well as being more efficient in the first place, LED street lights can be on motion sensors, allowing them to remain off most of the night without a safety implication.
"So as well as being more efficient in the first place, LED street lights can be on motion sensors, allowing them to remain off most of the night without a safety implication."
People don't like dark streets. The current incarnations of these things run at 10-30% brightness until there's motion under them - and they signal adjacent lamps to brighten up too.
There are some quite interesting youtube videos about this stuff if it floats your boat - and bear in mind that a 90% reduction in lumens is only a subjective halving of brightness thanks to the human eye being logarithmic in sensitivity.
The real win in leds vs traditional luminaires in streetlighting isn't the reduced power consumption. The saving in energy costs are utterly dwarfed by the cost savings associated with getting a bloke in a bucket up the pole to change the lamp - theres a 5:1 reduction in labour costs.
@AndyS - Marcus Aurelius does have a point. You only have to look at what happened when mains reflector halogen lamps (GU10) came along. They started a whole fashion in excessive lighting. With bulbs and fittings being cheap as chips, you'd get one 100W pendant lamp being replaced with a dozen 50W halogens. LEDs will also be sold for fashion rather than practicality, their size and low heat output allowing a whole new generation of lighting which will be exploited because it looks different, not necessarily because it can be made to consume less power for a given light output.
I agree that the step change in efficiency between halogen and LED is a lot greater than between conventional incandescent and halogen, though.
"LEDs will also be sold for fashion rather than practicality, their size and low heat output allowing a whole new generation of lighting which will be exploited because it looks different, ..."
Until it goes out of fashion, that is. Fashion is inherently over-priced and costly, but it is also transitory.
In the mean time, using an LED for its basic purpose -- light -- will always be cheaper than the equivalent incandescent, even if you add a few extra bulbs1. This is what the Defenders Of Incandescents (a tinfoil hat subsidiary) keep trying to draw our attention away from.
---
1. I doubled the number of bulbs in my kitchen, bringing the wattage to ... 24. Still a bit less than the original 175 watts.
I must admit that I didn't realise just how big a deal this was until I stumbled across some information on it a few years ago. Once I read through the story and how involved it was and what has been enabled since I simply assumed they already had a Nobel prize!
Congratulations to these folks - now that I know the story it is a great achievement and one that has really enabled a lot of technology to advance to a state that we now take pretty much for granted.
Where's the sake icon? (Though beer has an excellent history in Japan too!)
On a FB (yes, I know) group someone was recounting thier experience as main sparks at a festival.
The festival peeps were happy as pigs in shit about the way that LEDs had broken through for stage lighting but there was so much cheap Chinese LED lighting designed purely for output that old fashioned things like PF correction had been ignored.
In order to re-balance the loads the sparks had to set up about 50kw of extra loading to keep the generators happy..
Another related issue with stage lighting, even the better units, is the amount they leak to earth. I'm no expert on the electrical design of LED dimmers (it's PWM and black magic) but it seems the most common way to design them involves dumping a lot of noise to earth. This in turn plays merry hell with RCD's - it looks to them like current leakage and they trip. Fine if you're supplying your own distribution, or have a guy like Elmer Phuds friend who can make arrangements for you, but when you show up at a hotel \ conference centre with everything on 30ma trips it can provide an extra problem to worry about.
Whilst we're at it, a more lighting designer rant: only the very best units provide decent colour rendering and skin tones - cheapy RGB units look horrid as front light, but still seem to turn up there, when cheap traditional halogens would do a far better job.
Biggest issue with LEDs as the moment is the circuits that people run them off. Typically the LED products currently on offer benefit from running directly off 12V or 20V DC supplies.
A lot of the issues currently seen is with the cheapy power electronics bunged into the package to make then run off 240V/110V AC - which throws out noise and ultimately goes pop long before the LEDs.
While it would be the correct action, I can't forsee many people dashing to re-wire their house lighting circuits, replacing cheapo twin + earth run straight off the CU with a high quality rectifier/converter and second DC fusebox. Without this you ain't gonna see the 14 year lifetimes.
All LED bulb assemblies, whether mains or 12V, contain a bridge rectifier and a switch-mode power supply (LED driver). So the difference isn't as stark as you might expect, but I agree that it seems it should be easier to make a cheap reliable 12V AC LED driver than a mains one. I have eight 3W MR16 LED fittings (12V) in my hall/stairs which, despite being imported from a Chinese tat bazaar, are still working apparently perfectly after several years.
Not necessarily. A lot of research and development has gone into components to run AC/DC conversion straight off the mains.
However, you need a bridge rectifier at some point and the typical forward voltage on these is around 1.6V. If you are rectifying 12V AC, a higher proportion of the available voltage is wasted pushing electrons through the rectifier than if you are using 110V or 230V.
The most efficient solution would be a decent sized AC/DC converter driving a house DC bus which supplied all the LEDs. Doubtless when the last incandescent lamp fanatic has been buried at a crossroads with a stake through his heart, someone will produce conversion kits that supply around 48V SELV to the existing lamp wiring, though the switches would need replacing as they are not designed for DC. Since house wiring is designed for incandescents, the capacity would be adequate.
"Though the switches would need replacing as they are not designed for DC."
That's all about arc supression (AC arcs are self-extingushing every half cycle) and the reduced currents of solid state lighting mean that it isn't an issue anyway.
On a more practical basis, with "internet of things" meaning controllers fitted in luminaires, switches are redundant anyway. Home automation systems have done away with them for years, with the "switch" being a simple remote control and the next step is for that to become ubiquitous.
yeah. Dimmers are bad boys with RFI and that means earth leakage with the filters.
As for emission spectra, again, yep. NOT ideal. daylight is broadband thermal emission, 'woite' leds and so on are lots of narrow band emitters.
I reckon that will get cracked eventually. But for now stick to incandescents.
Whiteleds are getting better every year.
The new flatplate COB phosphors are getting pretty close to flat wideband emission when viewed through a diffraction grating (cheap hint: a CD makes a very good diffraction grating mirror to see the rough spectral spread of any lamp. Most CFLs are awful compared with even the nastiest "white" leds.
LED wavelength is too long compared with Mercury Discharge UV. Cheap high efficiency CFLs have poor colour rendition. Lower efficiency 'better' phosphor mix CFLs are not as good as Halogen, but FAR better than any existing 'White' LED at any price.
There is also an issue with phosphor life and light diffusion. If even overall lighting and good colour rendition is needed then CFL is far better. If daylight quality colour is needed, then you need Halogen. As halogen is continuous perfectly smooth spectrum the colour temperature can be adjusted on electronic Photography easily. Better colour temperature Halogen are more efficient but sadly much shorter life.
My GF has a water kettle that is backlit by blue leds. I see it as a good thing, that such an important discovery has reached the point where the average Joe sees, and dosn't flinch at blue - in many cases, expects it.
It's unlikely many of the average Joes will understand or at least appreciate the work that went into it, but like their car engines, GPS, PCs or phones, they're not going to understand the work and maths that went into those things as well - but it doesn't matter...
As average Joes, I hope can at least not take our gadgets for granted, and thank whoever created it for making it cheap enough we can use in our everyday lives.
Good work guys.
I grew up around red, green, yellow LEDs, and remember the era when blue was the New Cool because it hadn't been possible before. But that was YEARS AGO, and it's been overdone to death since. Now I'm sick of new gadgets lighting up blue, it's just not as trendy as they seem to think it is. It's not even that pleasant to look at. Give me amber or green over blue any day - far easier on the eye.
I agree, but I think some of it is the horrendous overbrightness of a lot of blue LEDs. In the old days, LEDs were very inefficient and so much more muted. High-efficiency/brightness ones cost more; it seems nowadays they don't so they put them everywhere.
I always thought yellow ones were just green and red superimposed. IS2R a very exciting LED in Tandy when I were a lad ... it was green if you powered it one way, red the other and yellow when connected to AC - I had always assumed it was a red and green lumped together the opposite way round to each other.
There is a new technology based on this exact effect, using a 4 way emitter R/G1 G2/B so 2 physical diodes in a 3 lead package.
It allows the typical cluster based emitters to emit a wider range of greens than normal for a minor increase in driver complexity, at double the normal resolution.
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