Published on January 9th, 2013 | by James Ayre2
Brighter LEDs Inspired By Fireflies, Efficiency Increased By 55%
January 9th, 2013 by James Ayre
A breakthrough in the efficiency of LEDs has been made thanks to new research that investigated how fireflies create their light. By utilizing a newly discovered pattern of jagged scales on the fireflies’ abdomens, LEDs 55% more efficient than previous designs have been created.
Researchers used the newly discovered pattern to make an LED overlayer that mimicked the structure on the fireflies. This overlayer increased LED light extraction very considerably. And it “could be easily tailored to existing diode designs to help humans light up the night while using less energy,” the Optical Society of America notes.
“Fireflies create light through a chemical reaction that takes place in specialized cells called photocytes. The light is emitted through a part of the insect’s exoskeleton called the cuticle. Light travels through the cuticle more slowly than it travels through air, and the mismatch means a proportion of the light is reflected back into the lantern, dimming the glow. The unique surface geometry of some fireflies’ cuticles, however, can help minimize internal reflections, meaning more light escapes to reach the eyes of potential firefly suitors.”
The light-emitting diodes, or LEDs, used by humans have the same problems with internal reflection. So by copying the patterns used by the fireflies, much greater efficiencies than have been previously achieved are possible. Specifically, the researchers created a jagged overlayer that was placed on top of a “standard gallium nitride LED.”
They “deposited a layer of light-sensitive material on top of the LEDs and then exposed sections with a laser to create the triangular factory-roof profile. Since the LEDs were made from a material that slowed light even more than the fireflies’ cuticle, the scientists adjusted the dimensions of the protrusions to a height and width of 5 micrometers to maximize the light extraction.”
Researchers have previously copied other features of firefly lanterns, but almost entirely on the nanoscale, as changes at a larger scale were assumed to be less effective for increasing efficiency. This assumption was made because these previously unresearched features are larger than the wavelengths of visible light are. This new research is the first that has identified these micrometer-scale photonic features, and to the surprise of the researchers, these features increased light extraction considerably more than the smaller nanoscale features.
The researchers currently think that commercial technology based on their findings should be available within the next couple of years.
The new research was just published in a pair of papers in the Optical Society’s (OSA) open-access journal Optics Express.
This research is another in a number of recent breakthroughs in LED technology, and also potential uses and applications, including: space farming, spray-on LED wallpaper, and combating seasonal affective disorder.
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