The light extraction efficiency of LED is 73%

PHILPS researchers said: thin 700 nm GaN based light-emitting diodes used in the experiment

In toward the final realization of high power light extraction efficiency, high brightness light-emitting diode, researchers at PHILPS Lumileds company (California San Jose) and PHILPS Research Laboratory (Eindhoven, Holland) created a blue emitting LED, the LED uses a photonic crystal structure, to reach a crystal light emitting diode light extraction efficiency 73%

In fact, the efficiency of the LED reached unencapsulated, there are two important reasons. First of all, organic materials are used to light emitting diode encapsulants degradation of high intensity, so it is not suitable for high power LED.

Secondly, the use of sealing materials to reduce the brightness of the LED, which is because the sealing material, which has a higher refractive index than the air, is a direct contact with the LED transmitter. If there is more than one air gap, an increase in the "optical size" leads, which means that the light gets rid of the transmitter at a higher angle into the sealing material. For a typical package of LED, its brightness is reduced by about a factor

In gallium nitride (GaN) - based, LED is very thin (700 nm) with a hexagonal photonic crystal on its surface, and its mode is a lattice constant of 455 nm and a depth of 250 nm. The new version of outdoes in other photonic crystal light-emitting diodes is, at least in part, because it is so thin that it is possible to enable the researchers to optimize the light mode allowed by the light emitting diode.

The light emitting diode consists of multiple quantum wells grown on sapphire, the peak wavelength of the emitted light is 450 nm, the size of 200 microns and 200 microns. The reflector is based on the emission of low loss silver light, in the rest of the material found (non extraction), the researchers made a simulation and found that about half of the light is absorbed by the quantum wells, the other half is reflected.

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