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Atomic-Scale Investigations Solve Key Puzzle of LED Efficiency


MIT and Brookhaven Lab scientists use electron microscopy imaging techniques to settle a solid-state controversy and raise new experimental possibilities.

From the high-resolution glow of flat screen televisions to light bulbs that last for years, light-emitting diodes (LEDs) continue to transform technology. Their full potential, however, remains untapped, in part because the semiconductor alloys that make these devices work continue to puzzle scientists. 
A contentious controversy surrounds the high intensity of one leading LED semiconductor-indium gallium nitride (InGaN)-with experts split on whether or not indium-rich clusters within the material provide the LED’s remarkable efficiency. Now, researchers from the Massachusetts Institute of Technology (MIT) and the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have demonstrated definitively that clustering is not the source. The results published online advance fundamental understanding of LED technology and open new research pathways.

CFNs Kim Kisslinger with a focused-ion beam instrument

CFN's Kim Kisslinger, seen here with a focused-ion beam instrument, reduced the InGaN samples to a thickness of just 20 nanometers to prepare them for electron microscopy. (Credit: Image courtesy of Brookhaven National Laboratory)

“This discovery helps solve a significant mystery in the field of LED research and demonstrates breakthrough experimental techniques that can advance other sensitive and cutting-edge electronics,” said Silvija Gradecak, the Thomas Lord Associate Professor of Materials Science and Engineering at MIT and a coauthor on the study. “The work brings us closer to truly mastering solid-state technologies that could supply light and energy with unprecedented efficiency.”
The research was supported by the Center for Excitonics, an Energy Frontier Research Center funded by the U.S. Department of Energy’s Office of Science. The work at Brookhaven Lab’s Center for Functional Nanomaterials was also supported by DOE’s Office of Science, with additional work carried out at the MIT Center for Materials Science Engineering.
Brookhaven National Laboratory

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