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Researchers Conquer "LED Droop"

samzenpus posted more than 2 years ago | from the more-shine-for-your-dime dept.

Science 113

sciencehabit writes "Tiny and efficient, light-emitting diodes (LEDs) are supposed to be the bright future of illumination. But they perform best at only low power, enough for a flashlight or the screen of your cellphone. If you increase the current enough for them to light a room like an old-fashioned incandescent bulb, their vaunted efficiency nosedives. It's called LED droop, and it's a real drag on the industry. Now, researchers have found a way to build more efficient LEDs that get more kick from the same amount of current—especially in the hard-to-manufacture green and blue parts of the spectrum."

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Let me guess (5, Funny)

busyqth (2566075) | more than 2 years ago | (#39947865)

The solution is called "LED Viagra"?

Re:Let me guess (5, Funny)

Anonymous Coward | more than 2 years ago | (#39947935)

Contact a doctor if you LED lasts more than 100000 hours.

Re:Let me guess (2)

Khyber (864651) | more than 2 years ago | (#39950551)

Fuck that, contact me, I'll give you a contract! The porn studios would love it!

Re:Let me guess (1)

JosephTX (2521572) | more than 2 years ago | (#39951025)

I don't know, the lighting is usually pretty good on those sets.

1st? (-1)

Anonymous Coward | more than 2 years ago | (#39947897)

1st?

Re:1st? (-1)

Anonymous Coward | more than 2 years ago | (#39947931)

Nope, 2nd. At least it's not that lame gamefucker crap spam.

Re:1st? (-1)

Anonymous Coward | more than 2 years ago | (#39948263)

Or the Microsoft shills trashing Google.

Re:1st? (-1)

Anonymous Coward | more than 2 years ago | (#39948267)

Or the Google fanboys trashing Apple.

Re:1st? (-1)

Anonymous Coward | more than 2 years ago | (#39948343)

Or the Apple fanboyz trashing Microsoft.

Re:1st? (-1)

Anonymous Coward | more than 2 years ago | (#39948431)

Or the Apple fanboyz trashing Google, Oracle, Microsoft, Motorola, Nokia, Walmart, Amazon, Purdue, moar.

Re:1st? (-1)

Anonymous Coward | more than 2 years ago | (#39949329)

Go Linux!

Ahhh that explainsPhilips' LED bulb (5, Interesting)

cpu6502 (1960974) | more than 2 years ago | (#39947961)

I guess that's why their new LED burns-up 26 watts but only created the equivalent of a 100 watt bulb. They are losing efficiency because the LEDs are being driven to high powers. (Lower power 25W or 40W bulbs only use 3 and 6 watts.)

Re:Ahhh that explainsPhilips' LED bulb (2)

mlts (1038732) | more than 2 years ago | (#39948141)

That does get me wondering... how better will bulbs made with this high current technology save electricity compared to other types of bulbs such as CFLs?

Of course, compared to the old incandescent, they will do much better due to more light and not heat.

Then there is usable life. With more current comes more heat, and heat is what trashes ICs.

Re:Ahhh that explainsPhilips' LED bulb (1)

Luckyo (1726890) | more than 2 years ago | (#39948555)

Another issue with incandescent is recycling them after they burn out.

Re:Ahhh that explainsPhilips' LED bulb (1)

unitron (5733) | more than 2 years ago | (#39950779)

Another issue with incandescent is recycling them after they burn out.

Are you sure you mean incandescent? The kind (glowing filament) for which Edison was famous?

Re:Ahhh that explainsPhilips' LED bulb (1, Informative)

Osgeld (1900440) | more than 2 years ago | (#39948739)

thats why your 1+ watt LED's usually come attached to a chunk of metal (unless you got them from china, then its metal painted plastic)

Re:Ahhh that explainsPhilips' LED bulb (3, Funny)

X0563511 (793323) | more than 2 years ago | (#39948997)

I think you mean lead painted with something else toxic to make it shiny?

Re:Ahhh that explainsPhilips' LED bulb (1)

RicktheBrick (588466) | more than 2 years ago | (#39952797)

Anyone can buy a CFL at dollar tree for a dollar. So anyone comparing leds should compare them to those CFLs. If they save money in a reasonable amount of time I would consider buying one. By reasonable, I mean 5 years at most.

Re:Ahhh that explainsPhilips' LED bulb (2)

cpu6502 (1960974) | more than 2 years ago | (#39955433)

IMHO all this talk of "saving energy" with lighting is ridiculous.
When I'm home I have 1 bulb burning. Sometimes none (I just use the light from the TV or LCD). That's 10 watts or 0.01 KWh per hour the bulb is on. Meanwhile my heat pump or air conditioner is running at 5,000 watts or 5 kWh per hour of use. We've totally messed-up our priorities by counting pennies and wasting dollars.

Re:Ahhh that explainsPhilips' LED bulb (4, Insightful)

Anonymous Coward | more than 2 years ago | (#39948691)

That's daft. With LEDs if you want more light, you simply use more LEDs. They are not bulbs, they're bloody diodes! Overdriving LEDs results in earth deaths, this has been known for 40+ years, keeping them within tolerances will ensure they'll last forever, or as near it in human terms.

Re:Ahhh that explainsPhilips' LED bulb (5, Funny)

ThePeices (635180) | more than 2 years ago | (#39948931)

" They are not bulbs, they're bloody diodes!"

Nobody uses bloody diodes for lighting. Not only is it un-hygenic, the loss of efficiency due to transmitting the light through blood is unacceptable, not to mention the red tinge to the light itself.

Everybody uses clean diodes.

Re:Ahhh that explainsPhilips' LED bulb (0)

Anonymous Coward | more than 2 years ago | (#39949121)

If only. Bad memories involving my gyno-light. Call it a headlamp or the staff at REI won't know what you are talking about.

Re:Ahhh that explainsPhilips' LED bulb (1)

RivenAleem (1590553) | more than 2 years ago | (#39955081)

Also,

"Roxanne, You don't need to turn on the Bloody Diode"

Doesn't really work.

Re:Ahhh that explainsPhilips' LED bulb (4, Interesting)

rtb61 (674572) | more than 2 years ago | (#39949317)

Now add that uplights provide the best quality illumination by reflecting light off ceilings. So rather than typical ceiling cornices, run strip leds around the perimeter of a room, with switching control to allow various switching patterns for dimming ie all on, 1 in 2 on, 1 in 3 on etc. Of course no goofy light fittings like chandeliers or fake oil lamps etc. just quality energy efficient controllable lighting example http://www.leyton-lighting.co.uk/led-tape.asp [leyton-lighting.co.uk] .

Re:Ahhh that explainsPhilips' LED bulb (0)

Anonymous Coward | more than 2 years ago | (#39950741)

No, those are far from the answer. All those LEDs have resistors on them. Those strips are fine for accents, but once to get to lighting large areas you will have a huge amount of wasted power in those resistors.

Re:Ahhh that explainsPhilips' LED bulb (0)

Anonymous Coward | more than 2 years ago | (#39951071)

That's a nifty stop-gap, but IMO direct illumination of the entire ceiling area with EL or OLED will be better, when we develop those techs to suitable CRI and efficiency.

Re:Ahhh that explainsPhilips' LED bulb (1)

Ginger Unicorn (952287) | more than 2 years ago | (#39952329)

That LED tape looks fun, pity there are no prices on their website.

Re:Ahhh that explainsPhilips' LED bulb (2)

Neil Boekend (1854906) | more than 2 years ago | (#39952513)

The full colour IP 65 with IR remote (5m) I bought a while back cost me E80 on a discount website. The dutch site I bought them at. [daydealers.nl]
The light intensity of 3 of them is "mood light". Not enough to read by but enough to have a background light while talking or watching a film.

Re:Ahhh that explainsPhilips' LED bulb (2)

arglebargle_xiv (2212710) | more than 2 years ago | (#39953035)

That LED tape looks fun, pity there are no prices on their website.

Go to any Chinese factory-outlet site like Alibaba or Dealextreme and you can buy these things in 10, 20, 50-metre rolls in any colour and power range you like.

Re:Ahhh that explainsPhilips' LED bulb (0)

Anonymous Coward | more than 2 years ago | (#39953355)

i too have noticed that light (especially LEDs) spreads out better when reflected off ceilings. however, i really don't your idea of running a strip of light around a room. i like the irony of having one torch sconce on each wall. sitting in each torch sconce is a 300-500 lumen LED flashlight. you turn on as many as needed for desired level of lighting or just the ones in the area of the room where you are working.

Re:Ahhh that explainsPhilips' LED bulb (3, Informative)

tlhIngan (30335) | more than 2 years ago | (#39950705)

That's daft. With LEDs if you want more light, you simply use more LEDs. They are not bulbs, they're bloody diodes! Overdriving LEDs results in earth deaths, this has been known for 40+ years, keeping them within tolerances will ensure they'll last forever, or as near it in human terms.

Problem is, driving more LEDs is tricky. Clusters wired in series a la Christmas lights die if one of the LEDs die (see Lights of America LED bulbs). Wiring them in parallel, you need to balance the current so one LED isn't being overdriven while the other is being starved for current.

A proper LED bulb like philips often have a driver circuit per LED (when you're dealing with 5W LEDs, it's not a bad idea), but the downside is adding LEDs means adding a lot of cost in driver circuits.

Dumb question (5, Interesting)

ShadowRangerRIT (1301549) | more than 2 years ago | (#39948109)

Why must a single LED provide all the light? Couldn't an array of, say, four LEDs, each equivalent to a 25W incandescent and using mirrors and/or lenses to even out the light distribution, get the same efficiency and substitute for a 100W bulb? Am I missing something obvious?

Re:Dumb question (5, Interesting)

cheater512 (783349) | more than 2 years ago | (#39948159)

I'd prefer a led slab. Rather than individual 'bulbs' on the roof illuminating a room, whats wrong with making the roof its self a big led panel.
Very even lighting, the individual leds would be very low current and relatively dim and it would look cool.

Mind you making that much sillicon substrate probably wouldn't be cheap, but you could perhaps cheat a little and use a layer like a screen's backlight has so you have less actual illumination points and it spreads it evenly across the roof.

Re:Dumb question (5, Interesting)

Grishnakh (216268) | more than 2 years ago | (#39948749)

That's impossible. Lights have to be in a bulb shape, because that's how they've always been, and people don't like change. Look how well circular fluorescent bulbs went over: like a lead balloon. Fluorescent bulbs in general only started taking off in residential applications when they made them so they'd fit in existing fixtures, which themselves aren't significantly changed in 100 years. Even worse, lamps aren't much different from the days when they were powered by gas: anyone who's built their own lamp (the kind that sits on a table, like a reading lamp) knows this: all the "electrical" parts are actually brass rods and fittings that were originally designed for gas, and were repurposed for wires, even though running lamp cord through them (particularly the joints) is a giant PITA and really doesn't make any sense.

Offices can do different things, like use 2x4 fluorescent fixtures, because they're more worried about efficiency (part of operational costs) and because they don't have dimwit cheap-ass home "builders" building them.

Re:Dumb question (2, Interesting)

Anonymous Coward | more than 2 years ago | (#39948875)

Dunno. That idea sounds pretty cool to me. Instead of having a flourescent lighting fixture in something like a dropped ceiling you could have LED panel that fits in the same place as one of those plaster tiles. Not quite one huge panel, but a more reasonable adaptation. If it's done right it shouldn't weigh any more than a typical ceiling tile either. Also, because it's not a fixture, if you don't like where the light is, it would be easy to swap it out with an adjacent ceiling tile. (Well, provided the cable drop for powering it is long enough. Never know what electricians do up there until you look inside the drop ceiling anyways.)

Re:Dumb question (1)

Alan R Light (1277886) | more than 2 years ago | (#39951399)

The fluorescent fixtures frequently used in offices are already made to replace one or two ceiling tiles. Not only could a new LED fixture do the same, but there are already LED replacement lamps that may increasingly replace the lamps in existing fluorescent fixtures. They're expensive right now, but expect prices to drop.

Re:Dumb question (1)

Grishnakh (216268) | more than 2 years ago | (#39955201)

Yes, an LED panel would make perfect sense and probably be a drop-in replacement for a 2x2 or 2x4 fluorescent office fixture. It'd also work great in a garage/workshop. But I don't ever expect to see LED panels in a residential home, unless it's custom-built by someone who's forward-thinking. Everyone else absolutely requires point-source lights, because that's how it's always been done, that's how residential fixtures all are, and we simply can't change.

Re:Dumb question (1)

legont (2570191) | more than 2 years ago | (#39949387)

We need iLight (c)

Re:Dumb question (1)

Grishnakh (216268) | more than 2 years ago | (#39955243)

You have a good point there. If Apple came along and started selling LED lights in different form factors (like panels) for residential applications, people would probably buy them like hotcakes, even if they cost an absolute fortune.

Re:Dumb question (5, Funny)

dadioflex (854298) | more than 2 years ago | (#39951029)

That's impossible. Lights have to be in a bulb shape, because that's how they've always been, and people don't like change.

I suspect in a lot of households, one half doesn't care what their "light bulbs" look like so long as they save them money, and one half doesn't care how much they cost to run so long as they look right in their decorative light fixtures. Typically the "it has to look right" half wins the buying decision.

Re:Dumb question (1)

Grishnakh (216268) | more than 2 years ago | (#39955303)

I think you're mostly hit the nail right on the head, but I do think another factor, at least in new houses, is that builders use whatever's cheapest and very rarely install newer technologies. That's why we have so many problems with stuff like low-flow toilets that clog all the time (there's lots of low-flow toilets that work great, but they're not the absolute dirt-cheapest toilet on the market, so builders won't use them unless they're building a custom house and the client specifically demands it).

Re:Dumb question (1)

Spugglefink (1041680) | more than 2 years ago | (#39952315)

...Running lamp cord through them (particularly the joints) is a giant PITA and really doesn't make any sense.

It's especially fun when you omit a spacer and shred the wire with the threads. Why does the circuit breaker trip every time I plug in this new lamp? Oh. Crap.

Re:Dumb question (1)

Grishnakh (216268) | more than 2 years ago | (#39955347)

Yes, exactly. The whole thing is completely idiotic, and if anything, some type of (wider-diameter) plastic tubes should be used, not brass. Or just nothing at all; the wire already has insulator on it, it certainly doesn't need metal tubes to protect it from the insides of the lamp.

Re:Dumb question (1)

Neil Boekend (1854906) | more than 2 years ago | (#39952525)

TL bars were already very common way before CFL's were concieved of (at least here in the Netherlands).

Re:Dumb question (1)

Grishnakh (216268) | more than 2 years ago | (#39955427)

Not here in the USA. We've had the big fluorescent tubes for ages (probably since the 50s or 60s), but they've only been used in offices and they caught on in personal garages or workshops. But inside the house? Never. Some manufacturers have tried to push tube-type fixtures for bathrooms and other rooms, but they never caught on. You might occasionally see one in a bathroom, but only rarely, and that's the only place. I got a couple about 5 years ago for a house I lived in at the time and they worked great; I think they used "T5" tubes.

Re:Dumb question (1)

drinkypoo (153816) | more than 2 years ago | (#39952675)

Fluorescent lights themselves cost more than incandescents, full stop. They cost more when you put them in and the replacements cost more. Home builders put incandescent sockets everywhere because they cost fifty-nine cents instead of twenty bucks for a halfway-decent fluorescent fixture.

Offices do different things, because efficiency is a real concern for them, because it's not practical to turn lights off during the day. Also, they are required by various workplace laws to have a certain amount of lighting, and when they call up a lighting engineer to get it, he's going to put in what he's used to putting in... which is a bunch of fluorescents.

Re:Dumb question (1)

quintus_horatius (1119995) | more than 2 years ago | (#39952889)

The "bulb" shape is frequently important because so many lampshades are designed to fit over them.

Re:Dumb question (1)

Petaris (771874) | more than 2 years ago | (#39954127)

Your right about the round fluorescent here in the US, but that doesn't apply everywhere. You see the round, and every other shape, fluorescent bulbs all over in Japan. Actually you can still find the round fluorescent bulbs in specialty lamps here too, my dad has one in his lab that has a magnifying glass in the middle, but that IS a specialty item.

Also, one of the reasons those haven't changed is because of the cost of changing perfectly good fixtures out just to fit a new bulb in them. If you haven't bought a fixture recently you may not have realized that they aren't cheap (with the exception of the junky ones you find on sale).

Re:Dumb question (1)

Grishnakh (216268) | more than 2 years ago | (#39955593)

Changing fixtures isn't a problem. You don't see people using dot-matrix or old ink-jet printers because the cost of changing a "perfectly good" printer is too much to change to a different ink cartridge; people buy the "fixture" first and worry about the consumables later. Sure, a 40-year-old table lamp isn't going to work well with a circular fluorescent tube, but how many people are using 40-year-old lamps? People buy new lamps all the time, but the new ones are still made exactly the same as the ones made 70 years ago. You don't see anyone making lamps in a totally new style to use a different kind of lightsource. Obviously, this isn't quite as practical with built-in fixtures (built into the ceiling or wall), but a lot of lighting still comes from table lamps and those haven't changed in a century. And it isn't that hard to change out residential fixtures (they sell them at Home Depot after all; that's a store for regular homeowners, not contractors), but there has been very little attempt to make new fixtures designed for different lightsources; I've seen a few bathroom fixtures designed for T5 tubes, but that's about it, and they never seemed to catch on anyway.

I'm not surprised things are very different in Japan. People there aren't stuck on having a house that looks like it was designed and decorated in 1850.

Re:Dumb question (1)

Petaris (771874) | more than 2 years ago | (#39955927)

I get your point. But I think the comparison to printer tech is a little bit too different to make a lot of impact. For example, the printers improved in other ways that were very important, size, noise, quality of print, etc. That is not the case for lamps or light fixtures for the most part, so you lack the real improvements that made the move from the dot matrix impact printers (which are still used and even sold) to inkjets and then lasers so worthwhile. That being said you have seen some improvements in lighting though its usually in specialized lighting fixtures, track lights with tiny high power xenon light bulbs for example. One other thing to consider is that the standard bulb socket is exactly that, standard. To really move things on to the next generation the companies that create the lamps and light fixtures will need to agree with the companies that create the bulbs/light emitting devices on a new standard. Coming from the IT world I think we both know how quickly and easily _that_ process goes.

Re:Dumb question (1)

RivenAleem (1590553) | more than 2 years ago | (#39955179)

Add a webcam and blam! instant ceiling mirror!

Re:Dumb question (3, Informative)

IANAAC (692242) | more than 2 years ago | (#39948241)

Why must a single LED provide all the light? Couldn't an array of, say, four LEDs, each equivalent to a 25W incandescent and using mirrors and/or lenses to even out the light distribution, get the same efficiency and substitute for a 100W bulb? Am I missing something obvious?

That's exactly what is being done now with many of these "shed' lights. I purchased a couple of these that have 20 LEDs inside a casing that has a highly reflective back (they're attached to small solar panels) for my cabin, since our electricity is quite prone to outages from all the thunder/lightning storms we have in Northern Wisconsin. Each one is enough to illuminate a 10x12 room on their own. I can read comfortably with just this light from pretty mch anywhere in the room.

They're not the prettiest lights, but I built a wood/translucent plastic shade, to make them at least a bit better looking. They also come with their own remote control switch so you can turn them on/off as you would any other sconce or ceiling light.

It's only a matter of time before some decent designs start coming out for these things.

Re:Dumb question (1)

ArcadeNut (85398) | more than 2 years ago | (#39948503)

(they're attached to small solar panels)

So you have Solar powered lights?

Re:Dumb question (2)

uncqual (836337) | more than 2 years ago | (#39948819)

Much better than that.

He has one small solar panel on the roof which powers the LED light in one room. Then he has a solar panel in that room which captures light from that room's LED to power the LED light in a second room. Then he has a solar panel in the second room which captures light from its LED light to power the LED light in a third room. Then he has a solar panel in the third room which captures light from its LED light to power the LED light in a fourth room. Then he has...

At night, he just shines an LED flashlight at the solar panel on the roof. This keeps all his rooms lit for several hours after dusk.

It also keeps most of the solar panels protected from the elements and puts them in places easy to clean.

Damn, I wish I had patented that idea.

Re:Dumb question (4, Informative)

IANAAC (692242) | more than 2 years ago | (#39948989)

You joke, but actually, each light array has a small 6x6 inch panel that your could mount either outside or hang in a window (the power cord from panel to battery pack is 16 ft. long). They provide enough energy to store in the enclosed small battery packs to last about 12 hours a charge. It's really not a bad solution to the problem.

In any case, energy is energy, whether it's generated at a coal plant and then distributed or directly to a battery pack for later use.

My point was really that, while they're currentlly not the most attractive lighting, that won't always be the case - they can be made fashionable as well as usable.

Re:Dumb question (3, Insightful)

Guspaz (556486) | more than 2 years ago | (#39948299)

Sure, and lots of applications do that already. There are drawbacks though: cost and space, for one thing, not to mention the different optical properties (focusing one light source versus focusing many).

If your sole goal is to just pump out a ton of light regardless of the cost or space, that's not a problem. But if you care about cost, or need to focus the light in a specific manner, it's a problem.

I suspect this is one of the reasons why LED-based projectors are still incredibly dim.

Re:Dumb question (0)

Anonymous Coward | more than 2 years ago | (#39948331)

It costs more money to add more components, and the cost of the number of lower powered components you'd have to add to get dramatic efficiency savings probably isn't worth it. You need to sell one of the most efficient lamps on the market at a reasonable price, not something that's twice as efficient as the next best but at ten times the price.

Re:Dumb question (0)

Anonymous Coward | more than 2 years ago | (#39949627)

This is an issue of house wiring. It would make wiring the house more expensive and complex. The fact that such wiring doesn't exists in any house, and there is little incentive for such an expensive renovation. As for new houses, the extra cost to construction would be too much except for rich houses.

Re:Dumb question (0)

Anonymous Coward | more than 2 years ago | (#39949679)

That's exactly what current consumer LED lightbulbs use; they employ a host of tiny LEDs. The breakthrough here still should make it easier to manufacture the lamps, since they can use a single LED in place of many.

Re:Dumb question (1)

CrimsonAvenger (580665) | more than 2 years ago | (#39949751)

Why must a single LED provide all the light? Couldn't an array of, say, four LEDs, each equivalent to a 25W incandescent and using mirrors and/or lenses to even out the light distribution, get the same efficiency and substitute for a 100W bulb? Am I missing something obvious?

People's houses have ceiling mounts that typically take from one to four bulbs. Lamps take one.

If you want to deal with anything other than that, you're talking replacing the hardware as well as the bulbs. Which is too expensive for many people, and too annoying for many more of them (who really wants to replace every light in your house just so you can use LED's, when CFL's already fit in the sockets?

So, yes, you're missing something. Existing infrastructure says people will be using things that fit into standard sockets for a long time to come.

Re:Dumb question (1)

ShadowRangerRIT (1301549) | more than 2 years ago | (#39950177)

Well, my point was that one socket could power multiple individual LEDs in a single "bulb." Not installing one LED per socket, but several LEDs powered off a single socket using a frame of roughly the same size as a regular bulb. Others have pointed out that they already do this to reach the power levels available now, and that it doesn't scale well in complexity and cost.

Re:Dumb question (1)

timeOday (582209) | more than 2 years ago | (#39950683)

Actually multi-LED units are dirt cheap [ebay.com] , so I'm still curious what's wrong with them.

Re:Dumb question (0)

Anonymous Coward | more than 2 years ago | (#39951059)

LEDS like those are sufficient only for ambient lighting, they don't give enough light to read by comfortably for instance, even at 60 or 78 diodes. Newer SMD type LEDs are far better for lighting a room, but they'll set you back $15-20.

Re:Dumb question (1)

Joce640k (829181) | more than 2 years ago | (#39951205)

Why must a single LED provide all the light? Couldn't an array of, say, four LEDs, each equivalent to a 25W incandescent and using mirrors and/or lenses to even out the light distribution, get the same efficiency and substitute for a 100W bulb? Am I missing something obvious?

If you look closely at the "high-power" LEDs that's exactly what they are.

eg. http://www.pbase.com/kds315/image/127711917/original.jpg [pbase.com]

Dali-LED (1)

camperdave (969942) | more than 2 years ago | (#39948123)

But they perform best at only low power, enough for a flashlight or the screen of your cellphone. If you increase the current enough for them to light a room like an old-fashioned incandescent bulb, their vaunted efficiency nosedives.

For a second there, I had images of LEDs hanging droopily over the edges of tables and tree branches [blogspot.com] .

Who cares! GOBAMA (-1)

Anonymous Coward | more than 2 years ago | (#39948189)

this is historic! gay marriage is just a step...

Clarify this for me (0)

Anonymous Coward | more than 2 years ago | (#39948275)

Now, researchers have found a way to build more efficient LEDs that get more kick from the same amount of current—especially in the hard-to-manufacture green and blue parts of the spectrum.

Correct me if I'm wrong but isn't it the exact opposite? The blue-green part of the spectrum the easiest and cheapest to get light out of using today's manufacturing techniques... hence why high color temperature, low CRI (6500K) cool white LEDs have higher output and lower costs than lower color temperature, high CRI (3500K) warm white LEDs.

Re:Clarify this for me (2, Interesting)

Anonymous Coward | more than 2 years ago | (#39948637)

Ahite LEDs of various color spectrums are totally different. They usually have a phosphorescent coating that creates the white light. The blue and green LEDs mentioned are single spectrum blue and green lights.

Re:Clarify this for me (4, Informative)

slew (2918) | more than 2 years ago | (#39949061)

Typically a "green" produced by GaN is fairly easy to manufacture and fairly efficient, but it is physically a very *hard* material. In contrast, the "blue-green" produced by InGaN (an alloy of a little bit of InN and base of GaN) isn't as efficient as it tends to have lots crystal defects and these defect cause brittle-ness and results in some electron-hole recombinations to be non-radiative (generating heat and not band-gap light emissions).

Regardless of this manufacturability issue, many white LEDs use an InGaN band-gap devices and create the "warmer" parts of the spectrum using phosphors. This makes most of the output light more blue-ish, but only the phosphor re-radiated (stoke's shifted) part in the warmer part of the spectrum where you pay the efficiency cost. For "cool" devices, less of the output is down-converted, so you have less efficiency loss. For "warmer" devices, more of the light is down converted and you pay for more conversion efficiency loss. Some warm devices actually have multiple LEDs (say a red, green, and blue), but color stability is generally hard to maintain over time and temperature, so these devices are generally less efficient and more expensive.

In any case, the effect that was described is that the currently "cheap" way of growing GaN base crystals for LEDs results in a polar orientation which is bad for high-current operation as it tends to generate a back field. This is described in more detail in this other site [cam.ac.uk] :

Most of the commercial GaN devices are grown along the [0001] direction, so-called “polar” or “c-plane” structures. However, there is an internal electric field perpendicular to the active regions in the c-plane devices as the c-axis is polar. This will result in band bending and a poor overlap of electron and hole wave-functions (the Quantum confined Stark effect, or QCSE), which reduces the radiative recombination efficiency and affects the device performance. In order to avoid (or reduce the effects of) the QCSE, GaN can be grown in “non-polar”, or “semi-polar”, orientations, in which there is no, or much less, internal polarization fields along the growth direction. In theory, this should increase the efficiency of light emitting structures. The high density of structural defects (such as basal plane stacking faults and partial dislocations) in heteroepitaxially grown non-polar and semi-polar GaN results in low internal quantum efficiency and output power of the devices, as reported in the literature.

Of course the answer is to just grow low-defect GaN in a non-polar or semi-polar orientation, but that's currently hard to do. These UCSB researchers aren't the only group working on this problem, but they apparently have done some cooperation with people doing actual manufacturing (Mitsubishi Chemical).

Re:Clarify this for me (2, Interesting)

Anonymous Coward | more than 2 years ago | (#39950131)

Slew is somewhat correct. The nonpolar/semipolar substrates are currently very expensive and small (1 sq. inch at best, compared to 12sq. inches for sapphire substrates that all commercial LED's, except Soraa's, are currently grown on). It has been prohibitively expensive for any other academic institution to do any meaningful research on nonpolar/semipolar GaN LED's and lasers. That is unlikely to change anytime soon. There are industrial companies working on it though. A few Japanese companies and the startup company owned by the UCSB professors, Soraa. This article does give a lot of hype, the 20-2-1 LED's aren't quite the magic bullet that it implies. But nonpolar/semipolar LED's probably are the future once Soraa, Ammono, or Mitsubishi Chemical figures out how to grow large bulk GaN nonpolar/semipolar crystals by the ammonothermal technique. Soraa is releasing (or already released?) an LED based on nonpolar/semipolar technology this year, and lasers probably later this year or next.

There are some good c-plane LED's for sure. Nichia's best c-plane LED's probably have 95% PEAK internal quantum efficiency, but they still have droop problems and are expensive.

Re:Clarify this for me (1)

MattskEE (925706) | more than 2 years ago | (#39956079)

Slew is somewhat correct. The nonpolar/semipolar substrates are currently very expensive and small (1 sq. inch at best, compared to 12sq. inches for sapphire substrates that all commercial LED's, except Soraa's, are currently grown on). .

I thought commercial LEDs had moved on to SiC substrates for the higher thermal conductivity, even though they're more expensive than sapphire. Most commercial GaN RF circuits and transistors (including Cree) moved on from sapphire a while ago are fabricated on SiC substrates, and a couple companies are doing GaN circuits on silicon substrates. I thought that Cree for sure would be growing their LED's on SiC given that they're the world's main source of SiC substrates, and based on their webpage that seems to be the case.

Re:Clarify this for me (1)

Anonymous Coward | more than 2 years ago | (#39954113)

I'm curious... how would you manufacture efficient greens with GaN only? Unless you dope it with something to widen the wells, it's only going to give you 330nm. My experience with LEDs is that all commercial blue / green (anything from UV to say 540 green) are InGaN. Not the indium clusters you mention - they are unreliable as hell, as you mentioned, but as a dopant in the gaN structure.

Re:Clarify this for me (1)

Anonymous Coward | more than 2 years ago | (#39954957)

I'm curious... how would you manufacture efficient greens with GaN only? Unless you dope it with something to widen the wells, it's only going to give you 330nm. My experience with LEDs is that all commercial blue / green (anything from UV to say 540 green) are InGaN. Not the indium clusters you mention - they are unreliable as hell, as you mentioned, but as a dopant in the gaN structure.

Unfortuantly, this was typo. I meant to say typically a "violet" produced by GaN (as used in blu-ray lasers). I don't think I mentioned Indium clusters, but InGaN alloys (perhaps that wasn't clear about InN and GaN being the alloy, but I was trying to say it in a way that is easier for most folks to understand and I though people would understand the word alloy rather than the complicated substrate/base/layer dopant/deposition growth technique that is used in commercial InGaN production to limit crystal defects, I still believe alloy of InN and GaN on base of GaN to buffer against crystal defects is a generally correct explaination to the first order approximation, but if I'm wrong, I'm wrong). I suppose I should proof read more before I hit submit, but this is of course slashdot and I usually just stream-of-unconcious type when I have something to say (including this post)...

Re:Clarify this for me (1)

Grishnakh (216268) | more than 2 years ago | (#39949559)

No. Red LEDs were the first LEDs made, and still are the easiest and cheapest to make light brightly.

Based on this breakthrough ... (1)

PPH (736903) | more than 2 years ago | (#39948325)

... we should expect to see kewl blue LEDs appearing on all major appliances in the next 3 to 5 years.

I hope not... (1)

publiclurker (952615) | more than 2 years ago | (#39948857)

That really sounds annoying.

Re:I hope not... (0)

Anonymous Coward | more than 2 years ago | (#39948915)

Too bad they already exist. blue and green LEDs are not a myth the article is about them having better efficiency at high power output, which would be very annoying.

Re:I hope not... (2)

Qzukk (229616) | more than 2 years ago | (#39949397)

I have a DVR with a blue power LED on front that apparently is just the right wavelength to be screwed with by my glasses. As I move my head around (or just move my glasses around) the LED appears to move around on the front of the thing. The closer to the edge of my glasses, the farther the displacement. I can even get it to overlap the other LEDs if I turn far enough, so it seems to just be that wavelength of light that's distorted, and it has to be a fairly narrow band that is affected since I've never noticed it anywhere else.

Drives me crazy sometimes, I try not to look at it.

Re:I hope not... (2)

necro81 (917438) | more than 2 years ago | (#39952571)

just the right wavelength to be screwed with by my glasses. As I move my head around (or just move my glasses around) the LED appears to move around on the front of the thing. The closer to the edge of my glasses, the farther the displacement.

It's called chromatic aberration [wikipedia.org] , and it is an unavoidable effect of light passing through lenses. When light passes through a lens, it gets bent, which is the whole point. But the amount of bending is wavelength-dependent, and so most lenses will act a bit like a prism and spread the spectrum of the incident light. The stronger the lens, the greater the bending, the more pronounced the effect. The effect is more or less nonexistent along the optical axis, but becomes more pronounced as you go out towards the edges of the lens, where there is both more material to refract through, and the deflection angle is that much greater. This is one reason why big telescopes don't use lenses except for the objectives: the big lenses you'd need for a big telescope would produce too much aberration. Reflector telescopes are, for the most part, immune to this effect, because a mirror reflects all (visible) wavelengths equally.

For myself, with worse than -6 diopter, polycarbonate lenses, I've just learned to live with the effect. It can actually be kinda fun, because it can be like wearing a spectrograph: by putting a light source off to one side of my field of view, I can see the constituent wavelengths. There is no noticeable effect when looking straight ahead.

Though not a problem for blue (4, Funny)

Trogre (513942) | more than 2 years ago | (#39948957)

If you increase the current enough for them to light a room like an old-fashioned incandescent bulb, their vaunted efficiency nosedives.

Apparently this droop issue is only a problem for non-blue wavelengths. At least if my subwoofer, PC and external HDD are anything to go by...

My eyes hurt.

Re:Though not a problem for blue (3, Interesting)

Khyber (864651) | more than 2 years ago | (#39950529)

Actually, that's just because blue is a higher energy potential. Blue wavelengths especially have hazard warnings, as that wavelength has known issues with triggering macular degeneration or making it worse.

Re:Though not a problem for blue (1)

adolf (21054) | more than 2 years ago | (#39950671)

FWIW, I find that placing red vinyl electrical tape over an eye-burning blue LED tones it down appropriately enough that it can still be seen, but is never too bright.

My application of it is sloppy, but at least I can look at the damned things once the tape is covering them. (I could trim the tape with a good knife if I cared, but I really don't.)

Amusingly, capacitive buttons (such as those on the external Lite-On DVD-R drive on my desk) still work fine even with the tape over top of them.

Re:Though not a problem for blue (1)

nadaou (535365) | more than 2 years ago | (#39952223)

I do the same thing with the tape, as I've never actually bothered to open the thing up and add a resistor in series. The farthest I've got is to take out the LED and grind the plastic housing so that it is flatter and rougher, to make it a bit more diffuse.

poor quality components (1)

Anonymous Coward | more than 2 years ago | (#39949085)

My experiment with LED each of the first 3 bulbs I bought lasted between 500 and 2000 hours est. I bought a different brand, one died the first week. I now use CCFL simply because while they use slightly more energy, they are 10% of the price and also burn out way too soon, but not any sooner than LED and the light is better too..

Rod

Re:poor quality components (2)

fast turtle (1118037) | more than 2 years ago | (#39949249)

and yet I just bought a 30 pack of 40 watt Incadescent bulbs for better lighting and environmental efficiency - No Mercury. Do they burn out any faster? Not as far as I've seen based on the quality of the damn CFL bulbs we've been able to get cheaply. Those don't last anylonger then an incadescent bulb and have mercury in them plus they look horid where I really need them.

What I'm doing now is moving towards the halogen based 12v bulbs in low voltage track light systems. quite a bit of light and can be run straight from a 12v source w/o converting to AC first. Very nice as I'm also moving off the grid and beginning to switch to a PV array due to planned rolling blackouts by Edison International this year. Getting tired of having my power go out every damn summer because no one want's to invest in power line maintenance.

Re:poor quality components (3, Informative)

wrook (134116) | more than 2 years ago | (#39949399)

CFLs burn out quickly if you cycle them. Once you turn them on, they shouldn't be turned off for 20 minutes. This makes them less than ideal for some locations (like the bathroom, hallway, etc). I currently have CFLs as the main lighting in areas like the living room, but LEDs in other areas. LEDs are expensive, but it's not like I'll starve if I spend a couple of hundred dollars on lights. Prices are dropping fast (at least here in Japan). It wouldn't surprise me if the cost per lumen approaches CFLs soon.

I've never been one to dislike CFLs. Personally, I like the color of "daylight" bulbls *much* better than incandescent. But I must say that I like my LEDs better than the CFLs. The biggest issue is that the lumens don't drop off as quickly through use. They also come to full brightness more quickly (basically instantly). I will probably switch over completely in the next couple of years.

Re:poor quality components (3, Informative)

sunspot42 (455706) | more than 2 years ago | (#39950861)

>I just bought a 30 pack of 40 watt Incadescent bulbs for better lighting and environmental efficiency - No Mercury.

Unless coal is used to generate some - or worse most - of the electricity where you live, in which case powering those incandescent bulbs will release far more mercury into the environment than an equivalent number of CFLs would.

Worse, the mercury that comes from burning coal isn't elemental mercury, as you'd find in a CFL. Which means it's far more easily absorbed by living things like us.

Re:poor quality components (0)

Anonymous Coward | more than 2 years ago | (#39949363)

If your lights are burning out like that, contact your electrical supplier. Or repair your in-house circuits.

I moved into my house in late 2009. I put in new cfl bulbs to replace the incandescent. I have not had to replace a burned-out CFL bulb yet.

Now the tube t12s I have had to replace, but they were already in the house, so I don't know their age.

I just got some LEDs last year, they're fine from what I can tell.

Re:poor quality components (1)

Khyber (864651) | more than 2 years ago | (#39950523)

So why not build your own? It is ridiculously simple, with the exception of a little math.

Not the only droop that needs to be solved... (1)

EmagGeek (574360) | more than 2 years ago | (#39949459)

There are other droops in life I'd rather see solved...

Underdriven monochrome LEDs more efficient (0)

Anonymous Coward | more than 2 years ago | (#39949537)

If you even further underdrive some types of monochrome LEDs, you can increase their efficiency even more.

http://donklipstein.com/led.html#ua [donklipstein.com]

Incandescent inneficiency (2)

rossdee (243626) | more than 2 years ago | (#39950103)

Since the have laws banning incandescent bulbs because they are inneficient, when are they going to do something about the large incandescent light source 92 million miles away? Not only is it inefficient, it is the major cause of global warming.

(PK so there might be some issues of jurisdiction, but the owner of said light source (Oracle) is in this country...

Re:Incandescent inneficiency (1)

Impy the Impiuos Imp (442658) | more than 2 years ago | (#39952593)

Well, it is self-powered, so we should model it, actually.

Come to think of it, I think we are trying and have been for 40 years.

45% overall efficiency, not bad (1)

Khyber (864651) | more than 2 years ago | (#39950517)

Pushing the diode at 200mA only resulted in an actual drop of roughly 8 points from that 52 percent. That's better than current blues used in my panels, which are top-line and only roughly 35% efficient.

But that isn't solving droop. Droop is the speed at which an LED driven at higher currents loses light output, which is a secondary byproduct of this. This mitigates the hell out of it, but doesn't solve the overall issue of light output loss over operative time.

But the higher efficiency is very welcomed. Applying this to create white diodes will let us smack roughly 250 lux/w when all is said and done, and with that, HID lighting has finally met its match, for good.

Odd comparison (0)

Anonymous Coward | more than 2 years ago | (#39951357)

The term LED droop is invented by the incandescent lightbulb industy. You can burn through a filament just as well. Its a problem which by telling people about how you solve it suggests your technology sucks..It is like comparing a primal scream and reading written language out loud and saying "language is nice but now scientist have found a way around the volume droop"..USA Dumbass-A

Stupid! Stupid! Stupid! (1)

Grindalf (1089511) | more than 2 years ago | (#39951793)

Use a MUCH higher rated LED than the actual usage LUX level output, that stops them browning off. Easy! I've done this loads of times ...

Re:Stupid! Stupid! Stupid! (1)

Neil Boekend (1854906) | more than 2 years ago | (#39952619)

That severely limits the max power you can stick in a standard bulb size space. Keep in mind that each led doesn't only need space to be in, but also a driver circuit(wich is bigger than the led itself, if done correctly).

Beware of too many LEDs (1)

scorp1us (235526) | more than 2 years ago | (#39953157)

Re:Beware of too many LEDs (1)

JRIsidore (524392) | more than 2 years ago | (#39955047)

What they did is they compared the light of LEDs and HID to that of sodium lamps, mostly found in outdoor lighting (for those who don't RTFA). The blue light, which is missing in the sodium spectrum, supresses the melatonin production. The same process happens every morning when you get up and turn on the light or go outside. As sodium lamps are mostly used in streetlighting etc. I think this is actually a benefit instead of being dangerous. Supressing the melatonin fights the fatigue which might prevent some car accidents, although I'm not sure if this effect is high enough for this.
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