Argonne National Laboratory

Shedding new light on LEDs

By Louise LernerApril 18, 2012

LEDs, or light-emitting diodes, are the secret behind your iPhone screen, flatscreen TVs, Christmas lights and crosswalk signals. They can last longer and save more energy than traditional incandescent bulbs. But there is one thing they aren’t very good at: efficiently emitting light in the yellow-green spectrum.

Argonne and Purdue researchers are peering deep into the atomic structure and composition of LED lights in order to build highly efficient LEDs in the yellow-green spectrum.

Purdue researchers Robert Colby and Eric Stach, experimenting with a type of LED based on nanopyramids, wanted to analyze the nanoscale composition of the materials they were creating. Collaborating with Nestor Zaluzec at Argonne National Laboratory’s Electron Microscopy Center, they imaged the structure and composition of these LEDs. From this work they were able to reconstruct a 3-D compositional map of these novel pyramids, which range from 100 to less than 20 nanometers in size. After measuring and visualizing the elemental distribution of gallium, indium and nitrogen within the structures, they found the active light-emitting region of the LEDs existed at the tips of the nanopyramids–where the indium was concentrated.

Read more at the Electron Microscopy Center website. A detailed description of this work can be found in Wildeson I.H. etal J. Appl. Phys. 108, 044303 (2010); doi:10.1063/1.3466998.