The Science of LED bulbs

The Science of LED bulbs

LEDs should light the way to a greener future: They use 75 percent less energy and last 25 times longer than incandescent bulbs, and they do a cooler temperature. But right now, we all use LEDs in electronics, as they have a bit of a problem fallen: at higher currents, the amount of light they produce takes a nosedive. 

The drop efficiency has puzzled scientists for years, but researchers at the University of California, Santa Barbara and the French Ecole Polytechnique say they have finally solved the mystery.

Their work, published in an upcoming issue of Physical Review Letters, identifies the source of the fall as a process called Auger recombination, a process that produces no radiant heat. Previous research at UCSB the theory that Auger recombination could be the culprit, but this is the first study to measure the effect conclusively.

LED lights contain a microchip with a positive-type and negative type semiconductor made of gallium nitride. Between the two, in a quantum well, the negative electrons of a semiconductor and electron holes combine the other, producing a photon of light. When more electricity is applied, produces more photons - to a point.

Droop City

Droop City: As the current increases, the efficiency of the blue LED starts to decline. Y. B. Tao et al. Phys. Status Solidi C, March 2012

In low power, such as your cell phone, the process works very well. But when the current rises to the level needed to illuminate a room, the nitride-based LED stop producing photons in the same proportion. According to research from UCSB Center for energy efficient materials, it is because the electrons collide and lose their energy through heat rather than light.

If we could get the LEDs to avoid this issue, which could replace compact fluorescent lights as energy saving light bulb in the future. Theoretically, the LED should produce about 300 lumens per watt, making them three times more efficient than CFLs, and easier to dispose of, as they contain no mercury. Widely adoption of LED lighting can save the country $ 265 billion and reduce our electricity demand by a third in the next 20 years, according to a 2010 estimate of the U.S. Department of Energy.

But it costs more upfront, so until LED technology can live up to its theoretical efficiency at higher currents, it is difficult to sell. While the U.S. already making energy sucking incandescent bulbs, LEDs are still controlling the market for commercial and residential lighting.

So far, we have a solution to the fall, but now we have identified the source of the problem, the researchers hope to design LEDs that minimizes the effect and produce more light, making the technology a more attractive option for home and lighting office.And the application of LED Display is also become more and more popular.