https://knowridge.com/2018/07/quantum-dot-white-leds-achieve-record-efficiency/
Looks very promising.
Thanks for the link.
That new developement is difficult to evaluate, with their way of making white light it is said to be easier to finetune the tint than with a phosfor layer, but despite it being difficult the manufacturers are doing a great job getting good tints with phosfor layers, for now more efficient than with this quantum dot technique. But that can change of course with further developement.
So the quantum dots emit green and red in a narrow band when hit by blue light. That makes me think that overall CRI won’t be any better than for RGB lights.
It sounds like they can be tuned to produce any color emission based on particle size so you could presumably mix a wide range of them in the right proportions to produce any tint and CRI you wanted, given enough different emission wavelengths. Perhaps more importantly is if this is true it seems the large scale cost to produce nice tint and high CRI LEDs would be the same as poor light quality LEDs so companies would just focus on making those instead and we can finally have good light quality, efficiency,and low cost all at the same time.
Neat-o, looks promising. Interesting that the quantum dots are “injected” as a liquid and held captive by the silicone dome, no dedoming.
The 105lm/W is far from a record, LEDs can do 200+ when driven low enough.
Even a regular XP-L at moderatecurrent gets above 100lm/W.
Quantum dot is good for screens because of the extremely narrow emission for each of red, green, and blue.
Unless you create hundreds or thousands of different quantum dot chemical compositions for every single visible wavelength it will never have good CRI.
Using quantum dot in a flashlight sounds like a horrible idea.
In a flashlight you want very wide, spread-out colour distribution, like sunlight or incandescent light.
In a tv or monitor you want only 3 tightly controlled wavelengths for red, green, and blue, like a laser.
But could say 50 different quantum dot emissions be mixed with existing phosphors to “fill in” some of the missing spectrum or replace some of the less efficient phosphors in the lower red spectrums. Or since (from my very rough reading) it’s based on the particle size not chemical composition as with phosphors could you produce them with a wide range of sizes in bulk to produce a full spectrum emission. Maybe it would be less efficient than phosphors overall.
Osram uses quantum dots in their upcoming Osconiq S3030 to get (cold binned) 173 lm/W with CRI90 and 3000K.
NOTE : Original link is now dead, because KnowRidge updated it with a newer article, on March 18th 2019:
Scientists redefine the low-cost semiconductors, called quantum dots
Interesting concept & could be a ground breaking improvement for many digital devices and LED flashlights.
Here’s the content in case KnowRidge changes the article link again:
In a new study, scientists found that tiny particles quantum dots may help develop low-cost semiconductors in the near future.
The easy-to-produce material may soon replace more expensive single crystal semiconductors and be used in solar panels, camera sensors, and medical imaging tools.
The study was done by researchers at Stanford University and the University of California, Berkeley.
Previous research showed that quantum dots have begun to break into the consumer market, but the long-standing uncertainties about their quality limit their usage.
In the current study, the team developed a new measurement technique to solve the problem.
They focused on how efficiently quantum dots reemit the light they absorb, which is one important measure of semiconductor quality.
This research is part of a project called Photonics at Thermodynamic Limits.
The goal is to create optical materials with the highest possible efficiencies. Optical materials are materials that affect the flow of light.
The team suggests that the quantum dots they can make in large numbers are as good as the best traditional semiconductor single crystals.
They hope their findings may help develop applications that require materials with luminescence efficiency well above 99%.
The measurements that the team has already developed are a milestone and may encourage more scientists to contribute to quantum dot research and applications.
This is the first measurement method to confidently show quantum dots could compete with single crystals.
The team’s next plan is to develop even more precise measurements.
If these materials reach efficiencies at or above 99.999%, then it opens up the possibility for technologies people have never seen before.
One lead author is David Hanifi, a graduate student in chemistry at Stanford.
The study is published in Science Mag.