RPI develops brighter whiter LEDs, partially solves current droop

Posted by Nino Marchetti

Troy (NY) - Are those LED lights you have at home not bright enough for you? Research being showcased at the Rensselaer Polytechnic Institute (RPI) has been targeted to address that issue with a new new type of light emitting diode (LED). Said to offer significantly improved lighting performance and energy efficiency, the researchers have partially solved the problem of current droop.





This new LED type, developed in collaboration with Samsung Electro-Mechanics, exhibits an 18 percent increase in light output and a 22 percent increase in wall-plug efficiency. This latter item is what measures the amount of electricity the LED actually converts into light. It is mostly being targeted at something called the "efficiency droop," a phenomenon that "provokes LEDs to be most efficient when receiving low-density currents of electricity, but then [begin]s to lose efficiency as higher density currents of electricity are fed into the device."






According to RPI, studies have shown that electron leakage might be a part of the problem. The researchers, focusing on the LED region where the light is generated, found that it contained materials with mismatched polarization. This polarization issue, which is likely causing the leakage, could be reduced by “introducing a new quantum-barrier design.” The new design allows that region's layers to have better polarization which, in turn, at least partially addresses the leakage issue.



"This droop is under the spotlight since today’s high-brightness LEDs are operated at current densities far beyond [the point] where efficiency peaks," said project leader E. Fred Schubert, head of the university’s National Science Foundation-funded Smart Lighting Engineering Research Center. "Our new LED, however, which has a radically re-designed active region, namely a polarization-matched active region, tackles this issue and brings LEDs closer to being able to operate efficiently at high current densities."



LED emitters in the red, green and blue color spectrum are required to produce white light. In the past, blue has been one of the more difficult colors to create. The ability to overdrive these new LEDs, relative to currents present in the older ones, will result in emitters that require less electricity for the same brightness, or that can be made much brighter on the same amount of input power.