Jpn. J. Appl. Phys. 45 (2006) pp. L910-L912 |Previous Article| |Next Article| |Table of Contents|
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Effects of Phosphor Application Geometry on White Light-Emitting Diodes
1Materials Department, College of Engineering, University of California, Santa Barbara, CA 93106-5050, U.S.A.
2NICP/ERATO UCSB Group, Japan Science and Technology Agency, University of California, Santa Barbara, CA 93106-5050, U.S.A.
(Received June 14, 2006; accepted July 22, 2006; published online August 25, 2006)
We fabricated white light-emitting diode lamps with three types of commercial yellow-emitting phosphors and studied the effects of phosphor application geometry. Two advantages were confirmed when low-concentration phosphor/silicone mixtures were employed: a 20% increase in output luminous flux and a reduced shift in the chromaticity coordinates upon change in diode current. We propose a simple model to describe these experimental results. According to the model, the results were attributed to reduced phosphor self-absorption (in the yellow spectral range) and reduced absorption saturation (in the blue spectral range), respectively, of the low-concentration mixture. The mathematical expression of the model will be effective for designing white light-emitting diodes based on the phosphor down-conversion technique.
KEYWORDS:solid-state lighting, light-emitting diode (LED), phosphor down-conversion, absorption saturation, self-absorption
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