White LED Breakthrough: Efficiency Doubles
by Michael Graham Richard, Gatineau, Canada on 11.20.05
It seems like the light emitting diode (LED) world is going from one breakthrough to the next. The last one was the accidental invention of warm white LEDs using quantum dots, and now a Japanese researcher at the Meijo University, professor Satoshi Kamiyama, has found a way to make white LEDs more efficient using a purple LED and a silicon carbide substrate. This new white LED has a brightness of 130 lumens per watt! "Normal incandescent light bulbs produce 15-20 lumens per watt; modern fluorescent bulbs produce between 60-110 lumens per watt; and current LED methods allow for a maximum of 60-70 lumens per watt. In short, if this is real, it's a big breakthrough." Professor Satoshi Kamiyama will establish a startup in January to manufacture and sell the LED units. He already has 40 million yen, but it is expected that other companies will want a stake in this. Thanks to reader Chris for the tip. ::White LED doubles efficiency, ::White LED Efficiency Breakthrough?, ::Brighter LED Break-Through
Is this a 'cool' white, or a 'warm' white? Cause the purply-blue-violet 'white' LEDs aren't very attractive. and for the kind of money they want up front, if they want to sell big time, had better look good,
The article doesn't say, but I think it is fair to assume that anything they plan to sell as a "regular" bulb replacement will emit warm white light.
Here's what I can't figure out: Why is it that no one is attempting to utilize phosphors (like the mix used in flourescent lamps) to change the UV rich output of the "bright white" LEDs into normal spectrum output? The conversion efficiency is almost 99%! Same goes for HID lighting..is anybody listening to this?
Erik: I think all the white LEDs currently on the market use phosphors that are very much like the ones in fluorescent tubes; that would be the obvious place to start research for a good phosphor for white LEDs. I would speculate that the reason that fluorescent tube phosphors don't make for good broad-spectrum white LEDs is because the underlying LED is emitting a single wavelength of UV light, whereas a fluorescent tube will produce a wide range of UV wavelengths for conversion into visible light by the phosphor.
If the reported "white light breakthrough" is as reported and the form of the light produced is acceptable it seems the days of incandescent and flouresecent lighting may be limited.
An Australian company, Lednium, and a US based subsidiary of TT Electronics, Optek, have produced a three-dimensional array of LEDs. The white version, with nine LEDs, reportedly produces 230 lumens with 10 watts.
If this same OPTEK/LEDNIUM technology incorporated the LEDs developed at the Meijo University we might well see LED based illumination that is capable of replacing incandescent and flourescent lighting.