LED research gets the green light

A team of researchers from Rensselaer Polytechnic Institute has received $1.8m in US federal funding to improve the energy efficiency of green light-emitting diodes.


A team of researchers from Rensselaer Polytechnic Institute has received $1.8m in US federal funding to improve the energy efficiency of green light-emitting diodes (LEDs).



As part of the US Department of Energy’s (DOE) Solid-State Lighting Programme, the team aims to close the “green gap” in LED technology by doubling or tripling the power output of green LEDs in three years. This advance could ultimately lead to the replacement of incandescent and fluorescent lamps in general illumination applications.



‘Making lighting more efficient is one of the biggest challenges we face,’ said Christian Wetzel, associate professor of physics at Rensselaer.



The DOE’s programme calls for the development by 2025 of solid-state lighting technologies that are more energy efficient, longer lasting, and cost competitive than conventional lighting.



The prime contender to meet this goal, according to Wetzel, is a white-light unit made from a combination of high-performance red, blue, and green LEDs. Researchers have made major strides in advancing the design of red and blue LEDs, but the technology behind green LEDs has lagged behind substantially, he says.



Wetzel says that green light is an essential piece of the puzzle because it addresses the peak of the human eye’s sensitivity, providing balance to the colours of red and blue light.



Researchers originally discovered that green LEDs could be made by simply adding indium (In) to the gallium nitride (GaN) materials that composed blue LEDs, but the materials produced to date have been inefficient, resulting in green LEDs that are too dim to be used for lighting homes and offices.



Wetzel plans to focus instead on aspects of the “piezoelectric effect”, where some materials produce an electrical field when pressure is applied. By controlling this effect, he and his colleagues hope to develop a process to make higher-intensity green LEDs that convert electricity into light more efficiently.