Are we nearing the limit of LED technology?

Are LED's nearing the limit of their performance? I know a new emitter will come along every now and then with a slight increase of output or preferable tint but as I understand it the increased heat is then a factor? So as the brightness increases, the increased heat (especially in smaller lights) means that high or turbo has to be regulated and steps down to a lower output to avoid overheating and damage.

How much further can we push LED technology in flashlights?

Is there anything new on the horizon?

In my view we are at the beginning,usage has a long way to go yet and it is in its infancy.

The flashlight industry is running hard. Every month new lights are released. Leds are getting brighter and more energy efficient. Problem is.. You don't 'need' a 1000 lumen EDC light using a CR123. Most manufacturers give their lights 2,3 or 4 modes. Sometimes they step away from that, and it has 5 modes but when lights get brighter, you need more modes. Most of use like a low mode but the mode spacing has to be good too. So in the future more brightness-levels have to be added. More lumens is nice but I prefer better runtime at this moment.

I wouldn't say it is in infancy, but neither is it a fully developed market. There is definitely still room for improvement. It probably won't be a single, disruptive change, but a series of incremental improvements as efficiency (electrical or thermal) gains are realized.

kj2 said:

Problem is.. You don't 'need' a 1000 lumen EDC light using a CR123.

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:banned:


Well not really.

But when we get to 1000lumen 1 CR123s its runtime at 100 lumen will be epic.

kj2 said:

Most manufacturers give their lights 2,3 or 4 modes. Sometimes they step away from that, and it has 5 modes but when lights get brighter, you need more modes. Most of use like a low mode but the mode spacing has to be good too.

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But most people don't go online to buy a flashlight, and the box stores are where they are bought most, and the box store-sold lights aren't made with the idea that we need more modes. They put out lights that have a 500 lumen setting, and a 250 lumen "energy saver" mode and think that's enough. Worse yet, multi-mode means 100 lumens for high, red light for mode 2, and then blue light for "blood tracking", which is of course something we all do on an everyday basis.

I just got back into flashlights. when I stopped 10 years ago my best light was a Surefire M2+A19+KT2 with a N2 bulb, was a throwmonster. Now it gets beat by a $10 no name cree T6 LED light light.

My EDC light 10 years ago was a Peak LED McKinley, used 7 5mm LED's. Now I just got a Armytek Partner C1 that is same size and 8 times brighter at least on high, even on low is 2-4 times brighter with same run time.

I think LED tech still has a long way to go.

Theoretical luminous efficacy limit for white LED with phosphorescence colour mixing is 260-300 lm/W according to old data (2010) on wikipedia.

Cree claim 200 lm/W with the new XP-L.

I am starting to think we are.

To me, the XP-G2 seemed like a rather minor upgrade for the R5, and it took forever.

...going from the Rebel to the R5, in comparison, felt like we were traveling at the speed of light!

( I saw what I did there )

thedoc007 said:

I wouldn't say it is in infancy, but neither is it a fully developed market. There is definitely still room for improvement. It probably won't be a single, disruptive change, but a series of incremental improvements as efficiency (electrical or thermal) gains are realized.

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In flash light technology maybe not but in terms of where the growth is we are at the baby stage.There are huge amounts to come in Domestic and Automotive use.

I hope that we still have some way to go. The latest LEDs may be able to reach 200lm/w at very low drive levels, but drive them at maximum spec and the XM-L2/XP-L drops to about 115 lm/w. Increasing high current efficiency is the key to increasing surface brightness. Cree could easily improve the thermal path of their existing emitters using current technology. e.g. they could build the emitter directly onto a copper board similar to the Luminus CST-90 (vs. SST-90). Better thermal path will go some way to improve high current efficiency and allow higher drive levels.

There's no law that says LED is the only answer either though, and another technology may eclipse it later for example.

In the mean time, outputs are climbing...and, things like smaller emitters can allow more throw, and other improvements can improve the CRI, etc.

Breakthroughs in cell designs will trigger new options as well, and so forth.

I think we are about half way there myself. As others have suggested claims of reaching the upper limits of efficiency are countered by the fact those figures are as the lower output of those "efficient" LEDs not the upper limits where more often than not the LED is pushed to. I think even when LEDs hit the theoretical max we will still see improvement in the lumen output per LED at that max figure also the quality of color rendition and cost. LEDs will get brighter cheaper, better color selection and then packaging will get such that they will be replaceable in devices too without resorting complex soldering and/or epoxy use.
I would like to see a return to 5mm LEDs improving them drastically such that sub 100 lumen lighting would be easy to deal with and dirt cheap. Imagine a 250 lumen/watt 5mm LED that puts out 25 lumens at 1/10th of a watt and has excellent tint and beam pattern for 75 cents each or less.

Current phosphor technology may be reaching it's limit, but there are always newer technologies being developed.

For the near future, crystalline super scintillators on ultraviolet LED die may be able to both emit more photons than phosphor and be tunable; vary color with voltage.

In the not so distant future, quantum electrons may cascade photons and create a tremendous amount of light per square centimeter. Heat could easily be managed by use of substrates composed of micro diamonds. Carbon nano tubes have the potential of exhibiting a duality; lower electrical resistance than even gold, while at the same time conducting very little heat.

LedTed said:

Current phosphor technology may be reaching it's limit, but there are always newer technologies being developed.

For the near future, crystalline super scintillators on ultraviolet LED die may be able to both emit more photons than phosphor and be tunable; vary color with voltage.

In the not so distant future, quantum electrons may cascade photons and create a tremendous amount of light per square centimeter. Heat could easily be managed by use of substrates composed of micro diamonds. Carbon nano tubes have the potential of exhibiting a duality; lower electrical resistance than even gold, while at the same time conducting very little heat.

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What he said! :duh2:

This thread reminds me of Clarke's three laws:

1. When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
2. The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
3. Any sufficiently advanced technology is indistinguishable from magic.

"I would like to see a return to 5mm LEDs improving them drastically such that sub 100 lumen lighting would be easy to deal with and dirt cheap. Imagine a 250 lumen/watt 5mm LED that puts out 25 lumens at 1/10th of a watt and has excellent tint and beam pattern for 75 cents each or less. "

Roger that.

Good topic. A couple of observations:

(1) Any theoretical limit is based on a model, which makes assumptions about the thing it's modeling. The Carnot cycle puts a theoretical limit of ~37% efficiency on internal combustion engines, but that's a heat engine. There is no such limit on electric motors, which are often over 90% efficient. We've all seen the ~260 lm/W limit for phosphor-based white LEDs quoted for several years on CPF. Meanwhile, Cree is now at 303 lm/W in the lab, so they've clearly overcome at least one assumption. And they're presumably not done innovating.

(2) It might seem that once you achieve 50% efficiency, the most improvement you can get is 2x. But that's not quite true. The ultimate limiter for both flashlights and fixed lighting is the ability to dissipate heat. Suppose you have a torch or fixture than can dissipate 10W of heat. Check it out:

At 50% efficiency, max power is 20W = 10W light + 10W heat
At 80% efficiency, max power is 50W = 40W light + 10W heat
At 90% efficiency, max power is 100W = 90W light + 10W heat
At 95% efficiency, max power is 200W = 190W light + 10W heat
At 99% efficiency, max power is 1000W = 990W light + 10W heat

I'm ignoring the battery problem, of course, but the point is: going from 80% to 90% efficient isn't about the extra 10%, it's about halving the heat, which allows you to either double the input power, or run the device at the same power but generate much less heat, which means it runs cooler, which means it's even more efficient. There's plenty more goodness coming our way.

That is a very good point.

Yes LEDs will max out at about 250lm/w for full spectrum 100CRI output, or <~400 for something acceptable as 'white' (THIS 2013 study is very comprehensive on the subject).

However, assuming battery technology is up to the task, as efficiency reaches maximum we will be able to input higher wattages into smaller lights, allowing the output of a certain sized light to increase much higher than what could be predicted solely by the efficiency increase itself.

so eventually even if leds dont change i will be able to buy an olight srmini mini ur mini. imr123 tripple xm-l2 2800 lumen beast
and an olight srmini x6 6000 lumen beast. nice.