Although LEDs are more energy-efficient than incandescent bulbs, it is reported that in most commercial models they produce light efficiency of only about 50%. This is called the light extraction efficiency, and the researchers greatly improved the light extraction efficiency by copying the fireflies. Many existing LEDs have an array of pyramid-like microstructures etched on their surface, which helps the light generated to exit the surface rather than be reflected back by it. Fireflies also have such structures on their belly "lanterns", which serve the same purpose.
However, Chen Changjiang, a PhD student at Pennsylvania State University, recently discovered that, unlike the microstructures on LEDs, those structures on insects are asymmetrical. He later discovered that the glow of some cockroaches was the same. With this in mind, Changjiang Chen and colleagues used nanoscale 3D printing technology to create microscopic asymmetric pyramid arrays on the surface of other traditional LEDs (as shown in the figure below). After testing, it is found that this makes the light extraction efficiency of the LED as high as 90%.
According to researchers, there are several reasons for the increased efficiency of LED light extraction. First, an asymmetric pyramid has a larger surface area than a symmetric pyramid, allowing greater interaction of light with the surface. Second, when some light is reflected back by two different angles of the pyramid, these reflections have a more random nature-this causes the light to reflect more.
Scientists are now seeking to collaborate with manufacturers to commercialize the microstructure application process, and they say it can be easily added to existing LED production facilities.
The research paper supervised by Professor Stuart Yin was recently published in the journal Optik.
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