Breakthrough Technology Accelerates Solid-State Lighting
: "Scientists at the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute have developed a method to get significantly more light from white LEDs (light-emitting diodes) without requiring more energy. ..
Commercially available white LEDs combine a light-emitting semiconductor with a phosphor, a rare earth compound, to produce visible white light. However, more than half of the light, or photons, produced by the phosphor is diverted back toward the LED where much of it is lost due to absorption. .. A research group, led by Dr. Narendran, developed a method to extract the backscattered photons by moving the phosphor away from the semiconductor and shaping the LED lens geometry. When combined, these changes allow the photons that would typically be absorbed inside the LED to escape as visible light. ..
Compared to commercial white LEDs, prototypes of the new "scattered photon extraction" (SPE) LED technology produced 30-60 percent more light output and luminous efficacy-light output (lumens) per watt of electricity. This means more visible light is produced without increasing energy consumption. Further research into the SPE technology could result in even higher levels of light output and greater luminous efficacy, according to Narendran.
The industry has set a target for white LEDs to reach 150 lumens per watt (lm/W) by the year 2012. The new SPE LEDs, under certain operating conditions, are able to achieve more than 80 lm/W, compared to today's typical compact fluorescent lamp at 60 lm/W and a typical incandescent lamp at 14 lm/W. " This is reportedly the first LED that is more efficient than a compact flourescent. 10:47:09 AM