Nanocrystal coating makes for warmer, increased efficiency LED lightsFebruary 2nd, 2008 - 5:06 pm ICT by admin
London, February 2 (ANI): A new study has shown that a coating of carefully tuned nanocrystals helps make LED light warmer and less clinical.
Hilmi Volkan Demir of Bilkent University in Ankara, Turkey, says that this development may pave the way for energy-efficient LED lights headway in the commercial market.
He has revealed that nanocrystals show promise to create LEDs that give off a warm white light, with efficiency far beyond compact fluorescents.
During the study, the researchers made nanocrystals from a core of cadmium selenide with a surrounding layer of zinc sulphide, and coated blue LEDs with a layer of such crystals.
They observed that the crystals absorbed some of the LED’s blue output, and emitted their own red and green light. Combining with the remaining blue light, the glow emitted by the crystals produced a soft white light, they say.
Although the existing commercial white LEDs are also based on blue LEDs, they use a phosphor coating that converts some blue light into a broad spectrum of yellow light.
Demir says that nanocrystals emit light in a much tighter range of wavelengths than phosphor, and thus make it possible to fine-tune the colour produced.
“Using combinations of nanocrystals, one can generate any emission spectrum as desired,” New Scientist quoted him as saying.
The researchers used two different sizes of nanocrystals, which emit particular wavelengths of either green light or red light. When the right mix of the two combined with blue light from the base LED, they say, it created a a warmer white with twice as much red as blue or green.
As compared to the commercial white LEDs that only provide about 30 lumens of light per watt of power going in, nanocrystal-coated LEDs were found to give off more than 300 lumens.
The result amazed researchers because fluorescents provide about 60 lumens per watt and traditional incandescent bulbs a measly 15 lumens per watt.
“The reported values are remarkable,” says In-Hwan Lee of Chonbuk National University in Jeonju, South Korea.
He, however, points out that making the core-shell nanocrystals is quite difficult.” (ANI)
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