LEDs for Solid State Lighting and Other Emerging Applications: Status, Trends, and Challenges
LEDs have been commercially available since the 1960’s, but in recent years there have been remarkable improvements in performance. These technology developments have enabled the use of LEDs in a variety of colored and white lighting applications. Colored LEDs have already become the technology of choice for traffic signals, much of interior and exterior vehicle lighting, signage of various types often as a replacement for neon, and other areas. LEDs are expected to become the dominant technology for most colored lighting applications. LEDs are beginning to penetrate white lighting markets such as flashlights and localized task lighting. With further improvement LEDs have the potential to become an important technology for large area general illumination. White LED products already have performance of over 30 lumens/watt which is nearly 3x better than incandescents. White LEDs with outputs of more than 100 lumens are already available commercially, and higher power devices can be expected in the near future. LEDs can be used as point sources, or can be used with light guides of various types to provide distributed illumination. Developments that will need to occur for LEDs to be viable for large area general illumination are discussed.
M. George Craford obtained a Ph.D. degree in physics from the University of Illinois in 1967. Craford began his professional career as a research physicist at Monsanto Chemical Company. He advanced to the level of Technical Director of the Electronics Division, before joining the Hewlett Packard Company in 1979. He is currently the Chief Technology Officer of LumiLeds Lighting, a joint venture of Agilent Technologies and Philips Lighting. Craford's research has been mainly focused on the development of visible LED's using a variety of compound semiconductor materials. He developed nitrogen-doped GaAsP technology in the early 1970's, which became one of the dominant commercial LED technologies. At Hewlett Packard, Craford's group pioneered the development of AlInGaP LED's, and has developed AlGaAs and InGaN products. Craford is a fellow of the IEEE and a member of the National Academy of Engineering. He has received technical achievement awards from a variety of organizations and received the 2002 National Medal of Technology from the President of the United States.
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