US research team aims to close the “green gap” in LEDs

A team of US researchers has received $1.8 million in federal funding to improve the energy efficiency of green LEDs.

A project entitled “High Performance Green LEDs by Homoepitaxial MOVPE”, which aims to improve the performance of green LEDs, has been awarded $1.8 million as part of the U.S. Department of Energy’s (DOE) Solid-State Lighting program, reports LEDs Magazine.

The team, led by Christian Wetzel and Fred Schubert of Rensselaer Polytechnic Institute (RPI), aims to close the “green gap” in LED technology by doubling or tripling the power output of green LEDs in three years.

Researchers have made major strides in advancing the design of red and blue LEDs, but the technology behind green LEDs has lagged behind substantially, says Wetzel. This has important consequences for applications such as illumination or backlighting of displays that may require the use of high-performance red, blue, and green LEDs to make white light.

The DOE’s solid-state lighting roadmap calls for the development by 2025 of advanced solid-state lighting technologies that are much more energy efficient, longer lasting, and cost competitive than conventional lighting technologies. The prime contender to meet this goal, according to Wetzel, is a white-light unit made from a combination of red, blue, and green LEDs – hence the need to plug the so-called "green gap."

Wetzel notes 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 colors of red and blue light.

He plans to focus on aspects of the "piezoelectric effect" -- a property of some materials that causes them to 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.