Researchers Conquer "LED Droop"

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."

Comments

Ahhh that explainsPhilips' LED bulb

[cpu6502]

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

[rtb61]

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.

Dumb question

[ShadowRangerRIT]

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

[cheater512]

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

[Grishnakh]

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

[Anonymous Coward]

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:Clarify this for me

[Anonymous Coward]

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

[Anonymous Coward]

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:Though not a problem for blue

[Khyber]

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.