An interesting article, but it makes me wonder: Do we have to worry about droop at all? If we can't make an LED produce lots of light at high power, then how about using lots of LEDs, each one at low power?
If someone points out that we don't know how to do this within certain price & size constraints, then I reply, fine, that's a problem to solve. So is droop. Solving either one of these problems get us the lighting we want. Is there any reason to single out droop as the problem that must be solved?
Yours is a good idea and is widely used right now as the standard reaction to droop.
As physicists we are interested in the droop problem because it is more fundamental to the structure and intrinsic nature of semiconductors and solids in general. It is along the same lines of: if we have type-2 superconductors that work at liquid nitrogen, why do we keep looking for SCs that work at room temperature, or if we have type-1 superconductors, why do we need type-2?
From a purely pragmatic point of view we know that more LEDs leads to the use of more money, more time, and more materials. A more efficient LED is a wise idea. I believe you may be missing a link here, that droop, or its physical cause, IS the entire problem that causes strains on price and size constraints. This is the reason to single it out.
I think it's the latter. I have been looking at proper led-lighting for my house a few months ago but when you want a lightbulb comparable to a 40W incandescence lightbulb it's filled with 80 LEDs (though it consumes only 4W). The cheapest I could find cost about €20,- while a simple incandescence lightbulb costs about €0,50.
I could also get 'High-Power' led-bulbs, filled with only 3 - 10 LEDs and producing the same amount of lumen but they all had a higher power consumption than the 80-led bulbs and strangely where more expensive (this probably has to do with heat removal requiring big heat sinks).
My super-bright LED flashlight runs on 1 AA and puts out as much light as my halogen bike light from a few years ago (which has a huge rechargeable battery pack).
This sounds like an engineering problem that will be solved (or at least mitigated). I remember how a few years ago we were told that silicon processes were nearing their limits, and then engineers figured ways to get around some of the perceived hard walls.
said hard limits don't apply to consumer level devices since they are concerned with economies and not absolute limits. it will be a long time before consumer level devices actually approach the hard limits that are still being talked about in the silicon world. by that time some new tech will take over.
I think they were incorrect in attributing the discovery of the LED. I thought it was discovered by a Russian engineer in the soviet union shortly before ww2. They attribute it much later and to a US company.
A light-emitting diode (LED) (pronounced /ˌɛliːˈdiː/[1], or just /lɛd/), is an electronic light source. The LED was first invented in Russia in the 1920s, and introduced in America as a practical electronic component in 1962. Oleg Vladimirovich Losev was a radio technician who noticed that diodes used in radio receivers emitted light when current was passed through them. In 1927, he published details in a Russian journal of the first ever LED.[citation needed]
Usually home improvement stores now carry them, I bought several and very pleased.
Although if you want super bright, go for the 10mm 100000mcd+ ones off ebay, 50 of them easily replaces a 70W light. I bought 1000 of them, cheap in bulk, and their a lot of fun. If you're making your own LED series don't forget to add resistor to limit the current.
I'd be suspicious of super cheap LEDs on ebay -- they may be cheap but they're unbranded and you don't know how long they'll last. And I'd definitely stay away from the ones that consist of 50 normal LEDs all pasted together. Normal LEDs aren't made to deal with the high current and heat you get from packing them together, so their lifetime is anyone's guess.
I've been putting in LED spots for my office (instead of 25W halogen MR16 lights). I've tried some off of ebay that (claim to) have Luxeon or Nichia LEDs. I've also gotten some from http://www.ledwaves.com/. All are pretty nice, but I haven't decided what color temp I like so currently there's a mishmash of cool and warm ones...
I bought an item (an audio connector) from Ebay and when I got it, it was clear it was from Maplin (like Radio Shack in the UK). But it was cheaper than Maplin, and a great buy, and I respect him for beating Maplin on postage (and they do charge too much) by combining orders and posting out at cost.
I have seen led lights - but they all are extremely expensive. If you want to use to replace incandecent bulbs, CFLs would be a lot cheaper (IMHO).
Some of my friends built their own lighting system and they ordered the LEDS directly from a mail order electronics store. This would probably be the cheapest.
The key LED manufacturer are working hard with all kind of R&D programs to improve the situation. I saw on a presentation lately that e.g. the new Osram high bright LED has an improved process addressing the issue. I agree that this is an engineering process improvement problem and will be mostly resolved over time.
They're well-written and seem to be scientifically accurate - a rarity on the web these days.