April 2012

Enhancing the Output of LED Lighting

Adding nanostructured regions to boost LED light output.

Click to enlarge photo. Enlarge Photo

Image courtesy of Claude Weisbuch, UCSB

Fig 1 Angular-resolved measurement of the output of a double embedded photonic crystal LED at a wavelength of 455 nm (emission in the blue).

The Science

By constructing light emitting diodes (LEDs) with two regions of embedded photonic crystal nanostructures, researchers increased the extracted light output efficiency, improving the performance of the LEDs.

The Impact

The ability to focus and increase light output opens the door to more efficient, brighter, and cooler operating temperature LEDs.

Summary

Light emitting diodes (LEDs) are beginning to have significant market penetration as sources of lighting in both residential and commercial applications. However, widespread deployment awaits further reductions in cost and improvements in efficiency. An LED’s performance depends on the details of the electronic and optical properties of its structure, which includes all materials: active, passive, semiconductors, metals, and insulators. One way to control and modify the LED performance is to structure the materials to incorporate a photonic crystal, a nanostructured region that modifies an optical medium to extract the light which would otherwise remain captured within the LED. Researchers at the Center for Energy Efficient Materials EFRC at University of California, Santa Barbara fabricated photonic crystals below and above the active regions of LEDs to improve their efficiency and enable new physical properties, including increased light directionality and polarization. The advantages of this device design are confinement of most of the guided light away from absorbing layers and an increased interaction between guided light and the photonic crystal regions. For this configuration, extraction efficiency improved by 40%. The fabrication of the embedded photonic crystals required specialized, multistage metal-organic chemical vapor deposition. This new design significantly increases the probability for light extraction, and thus is leading the way to improved LED performance and efficiency.

Contact

Claude Weisbuch
University of California Santa Barbara
weisbuch@engineering.ucsb.edu

John Bowers
Director, Center for Energy Efficient Materials (CEEM) EFRC
bowers@ece.ucsb.edu

Funding

DOE Office of Science, Basic Energy Sciences, Energy Frontier Research Centers (EFRC) Program; S.-C.H. supported by the Solid State Lighting and Energy Center at the University of California-Santa Barbara; Y.-L.H. supported by DARPA.

Publications

J Jewell, D Simeonov, S-C Huang, Y-L Hu, S Nakamura, J Speck, and C Weisbuch, “Double embedded photonic crystals for extraction of guided light in light-emitting diodes.” Applied Physics Letters 100, 171105 (2012). [DOI: 10.1063/1.4705735External link]

A David, H Benisty, and C Weisbuch, “Photonic Crystal Light-emitting Sources.” Reports on Progress in Physics 75, 126501 (2012). [DOI: 10.1088/0034-4885/75/12/126501External link]

Related Links

Center for Energy Efficient Materials (CEEM) EFRC

Highlight Categories

Program: BES, EFRCs

Performer/Facility: University

Additional: Technology Impact, Collaborations, Non-DOE Interagency Collaboration

Last modified: 12/6/2013 1:26:22 PM