Researchers at the University of California, Santa Barbara describes a light emitting diode (LED) in which light can be extracted mainly from two surfaces of the LED before entering a shaped optical element and subsequently being extracted to air. All of the layers of the LED are transparent for the emission of wavelength except for the emitting layer. For this reason, the LED light is extracted effectively through all of the layers. The combination of a transparent oxide electrode with a surface roughened nitride LED and shaped lens results in high light extraction.

File Number: 19169 

Web site: http://techtransfer.universityofcalifornia.edu/...

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Background
In a conventional LED, in order to increase the light output power from the front side of the LED, the emitted light is reflected by a mirror placed on the backside of the substrate or is reflected by a mirror coating on the lead frame, even if there are no mirrors on the backside of the sapphire substrate, and if the bonding material is transparent on the emission wavelength. However, this reflected light is re-absorbed by the emitting layer because the photon energy is almost same as the band-gap energy of the light emitting species. What is currently needed are LED structures that more effectively extract light.