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Proceedings Paper

Improved performance white LED
Author(s): Nadarajah Narendran
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Paper Abstract

This paper describes work leading to the development of a new packaging method for white LEDs, called scattered photon extraction (SPE). Previous work by our group showed that the traditional placement of the phosphor close to the die negatively affects the overall luminous efficacy and lumen maintenance of phosphor-converted white LEDs. The new SPE method enables higher luminous efficacy by placing the phosphor at a remote location from the die and by shaping the lens surrounding the die to extract a significant portion of the back-transferred light before it is absorbed by packaging components. Although the remote phosphor concept is not new, SPE is the first method to demonstrate efficient extraction of back-transferred light and show over 60 percent improvement in light output and efficacy compared to similar commercial white LEDs. At low currents, the prototype white LEDs based on the SPE technique showed over 80 lumens per watt. The SPE concept was tried on two types of commercial packages and both showed similar improvements.

Paper Details

Date Published: 14 September 2005
PDF: 6 pages
Proc. SPIE 5941, Fifth International Conference on Solid State Lighting, 594108 (14 September 2005); doi: 10.1117/12.625921
Show Author Affiliations
Nadarajah Narendran, Rensselaer Polytechnic Institute (United States)


Published in SPIE Proceedings Vol. 5941:
Fifth International Conference on Solid State Lighting
Ian T. Ferguson; John C. Carrano; Tsunemasa Taguchi; Ian E. Ashdown, Editor(s)

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