PHILPS photonic crystal LED light extraction efficiency of 73%

In the extraction of maximum light to high-power and high brightness LED efficiency forward, PHILPS LumiLEDs company (located in San Jose, Canada) and PHILPS Research (located in Holland City, the Huo Wen AI Undok) researchers developed an electronic crystal structure of blue LED, in the package, the light extraction efficiency is expected to reach 73%.

In fact, this light extraction efficiency is very important for an unsealed LED, for two reasons. First of all, the organic materials used in LED packaging are used for high strength degradation, so it is not suitable for high power LED.

Secondly, the use of packaging materials can reduce the brightness of LED; this is because the packaging material than the air has a higher refractive index, can directly contact with the LED transmitter. This means that, compared with the presence of air gap, the light emitted from the transmitter can enter the packaging material at a higher angle, increasing the LED "optical angle". For a typical packaged LED, its brightness is reduced to one of these two factors

Gallium nitride (GaN) - based LED is very thin (700nm) and has a hexagonal photonic crystal pattern on its surface, with a lattice constant of 455nm and a depth of 250nm. This new version of LED is at least better than other photonic crystal LED to a certain extent, because it is very thin, so that LED only allows to obtain optical mode, little so that researchers can generate few optical mode optimization.

LED is made up of multiple quantum wells grown on sapphire, the highest wavelength is 450 nm (nm), the size is 200 * 200 microns. The emitter is a low loss silver product. In order to figure out where the remaining light is, the researchers did a simulation experiment and found that about half of the light was absorbed by the quantum well and the other half was absorbed by the reflector.