US Department of Energy invests $6.4M in LED design

The DOE selects four projects that aim to "fill key technology gaps, provide enabling knowledge or data, and represent a significant advancement in the SSL technology base."

By Suzanne Deffree, Managing Editor, News -- Electronic News, 8/25/2009

The US Department of Energy (DOE) has announced four selections in response to its Solid-State Lighting (SSL) Core Technology Research Call that it will invest $6.4 million in.

The selections aim to "fill key technology gaps, provide enabling knowledge or data, and represent a significant advancement in the SSL technology base," the DOE said.

Three of the selected award recipients -- National Renewable Energy Laboratory, Pacific Northwest National Laboratory, and Sandia National Laboratories -- will see their projects funded via the American Recovery and Reinvestment Act at a total $4.6 million.

The National Renewable Energy Laboratory's project, "Lattice mismatched GaInP alloys for color mixing white light LEDs," seeks to demonstrate the viability of high bandgap GaInP alloys for synthesis of inexpensive, efficient Al-free LED devices on conventional GaAs substrates, which emit in the deep green 560 to 570-nm region of the green gap, or inside the red gap (615 to 625 nm), and for which the LEDs are fabricated using simpler OMVPE growth and processing techniques conventionally used for GaAs based III-V alloys. The DOE said that utilization of more efficient emitters, particularly in the deep green area of the spectrum, will contribute to meeting its efficiency targets identified for RGB based color mixing LEDs and significantly lower the cost of such devices.

Want to know more about LEDs? Don't miss EDN's October 2009 Designing with LEDs seminar and hands-on workshop in Chicago.

The Pacific Northwest National Laboratory's project, "Development of Stable Materials for High-Efficiency Blue OLEDs through Rational Design," aims to use new materials in a mixed-host system to demonstrate improved lifetime and efficiency. The DOE said that using new stable materials and improved OLED device architectures will allow higher device stability and improved efficiencies in blue OLEDs at currents useful for SSL products, and will lead to demonstration of highly efficient white OLEDs with longer lifetimes.
 
And Sandia National Laboratories' project, "Semi-polar GaN Materials Technology for High IQE Green LEDs," seeks to improve the internal quantum efficiency (IQE) in green nitride-based LED structures by using semi-polar GaN planar orientations for InGaN multiple quantum well (MQW) growth. The DOE said that these semi-polar orientations have the advantage of significantly reducing the piezoelectric fields that distort the quantum well band structure and decrease electron-hole overlap. At the end of this program, Sandia National Laboratories expects MQW active regions at 540 nm with an IQE of 50%, which with an 80% light extraction efficiency should produce LEDs with an external quantum efficiency of 40%, or twice the estimated current state-of-the-art.

The last recipient, the US ARMY Research Laboratory, will see $1.8 million awarded to its project via SSL appropriated funds. Its project, "Exploiting Negative Polarization Charge at n-InGaN/p-GaN Heterointerfaces to Achieve High Power Green LEDs without Efficiency Droop," aims to exploit the negative polarization charge at the n-InGaN/p-GaN heterointerface to achieve high-power, high-efficiency green LEDs without efficiency droop. The DOE said target goals are 540-nm LEDs with peak IQE of 40% at current densities sufficient to enable general illumination applications.