Quote Originally Posted by cture
Hello Kanna!
Tell me please if I have understood you right: you can find out most energy efficient led for a given wave length and assemble the prototype?
Not exactly. I can calculate accurately the efficiency of a given led, as anybody else interested on doing it.

And according to it, choose the better models for each given wavelengh you wish to use. Or if not precise wavelengh tuning required, i can say what model avalaible should give you better results for plant lighting.

LEDs wavelenght is a consecuence of chip molecular structure and composition. Manufacturers choose to produce chips wich emit the most usable wavelenght for many different applications and at what thay can get the best photometric output.

In the practice, it mean we can use blue and white leds very well, because their spectrums and peak wavelenghts are well suited to be used with plants. But on the red side, we have a problem. The highest photometric perfomance (lm) is produced with AlInGap chips emitting around 632-633 nm. At that peak wavelenght, the compromise between radiometric efficiency and photometric conversion is max, so manufacturers arnt really interested on producing other red wavelenghts in high power chips.

That mean that is very difficult to obtain chips emiting on longer wavelenghts, specially close to 660nm, wich would be the better for us. There is no a technical problem to do them, its just lack of interest of LED chips manufacturers. Indeed, AlInGap chips emiting at 650nm have the highest radiometric efficiency, that is what interest us.

But that wavelenght have only one main application (ours), and our demand is not enough to any manufaturer makes a production line of it.

So unfortunatelly, we cant get red leds of those wavelenghts at a cost effective price. We have avalaible a narrow range of wavelenghts between to choose what we prefer.

What i can do is helping in that task, by calculating of how many photons per burned watt emits each LED, so you can choose if using a 660nm peaked led emitting 1 uE/w or a 635nm LED emiting 1.3 uE/w, for example.

This should change on some years. Currently, all LED manufacturers are concentrated on developing high efficients white leds, and especially, warm white leds. This mean all the reseach funds are dedicated to InGan chips. Along the last 5 years, InGan (blue, green, white) leds have strongly improved its permomance (about 3x), while red leds are almost sttoped in their development.

But when the 150 lm/w has been reached on commercial LEDs (about 2 years, 3-4 for warm whites), then the competition is going to translate to improve the light quality. And this requires high efficiency red leds emiting on longer wavelenghts for color compensation. After years sttoped, now some companies are adquiring machines for AlInGap leds, preparing that time. Then we should have very high efficiency 650nm red leds easily avalaible.

But currently, its almost impossible to get them. The longer you can get on high power and efficiencies high enough are 640-645nm peaked red leds. And getting them is a headache (im already had spent last month discussing with distributors about it).