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25 August 2009


US Recovery Act funding goes to green LED research

The US Department of Energy (DOE) has awarded up to $6.4m in funding to four research projects focused on improving green LEDs and organic blue emitters.

Of the total, $4.6m has been provided via the American Recovery and Reinvestment Act, designed to help pull the US out of recession, in part through investing in new, energy-efficient technologies.

Much of the new funding is being channeled into work on improving green semiconductor emitters, in a bid to close the so-called ‘green gap’ - the region of the visible spectrum in which it is most difficult to fabricate efficient emitters from semiconductor materials.

Researchers at the National Renewable Energy Laboratory (NREL) in Colorado, Sandia National Laboratories in New Mexico, and the US Army Laboratory in Maryland will all receive funding to tackle the green problem, using three very different approaches.

The NREL team will attempt to reach the green through manipulating gallium indium phosphide (GaInP) alloys, traditionally used to fabricate red, orange and yellow emitters. They will seek to demonstrate the viability of a high-bandgap version of this semiconductor to push to the shorter wavelengths required for green emission.

Sandia’s team will focus on a different semiconductor entirely, using gallium nitride (GaN) substrates to improve the efficiency of green emitters, while the Army team will aim to exploit negative polarization charge in the active region of green LEDs.

Each of those projects is receiving $1.8m in DOE funding, while the remaining $1m has been awarded to the Pacific Northwest National Laboratory in Washington. Researchers at PNNL are working on organic devices, and will use the money to develop new, stable materials suitable for emitters working in the blue part of the visible spectrum.

Unlike inorganic light emitters, where the problem region has traditionally been the green spectrum, with organic devices the long-term stability of blue devices has always been the major stumbling block.

All of the projects fall under the DOE’s solid-state lighting core technology research program, and are aimed at improving the efficiency and quality of solid-state white-light sources.

See related items:

DOE selects projects for Round 5 SSL Core Technology and Product Development funding

PolarCoN project awarded €2m to close ‘green gap’

Search: Green LEDs Green gap GaInP GaN substrates


The author Michael Hatcher is a freelance journalist based in Bristol, UK.