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Research Papers

Phosphor Concentration Effects on Optothermal Characteristics of Phosphor Converted White Light-Emitting Diodes

[+] Author and Article Information
Jiun Pyng You

Optoelectronics Packaging and Materials Laboratories, University of California, 916 Engineering Tower, Irvine, CA 92697jpyou@uci.edu

Yeong-Her Lin

Optoelectronics Packaging and Materials Laboratories, University of California, 916 Engineering Tower, Irvine, CA 92697yeonghel@uci.edu

Nguyen T. Tran

Optoelectronics Packaging and Materials Laboratories, University of California, 916 Engineering Tower, Irvine, CA 92697ntran3000@yahoo.com

Frank G. Shi1

Optoelectronics Packaging and Materials Laboratories, University of California, 916 Engineering Tower, Irvine, CA 92697fgshi@uci.edu

1

Corresponding author.

J. Electron. Packag 132(3), 031010 (Sep 30, 2010) (4 pages) doi:10.1115/1.4002298 History: Received November 09, 2009; Revised June 16, 2010; Published September 30, 2010; Online September 30, 2010

The thermal and optical characteristics of phosphor converted white light-emitting diodes (LEDs) with different phosphor concentrations ranging from 4wt% to 13wt% are investigated. The light output of LEDs with higher phosphor concentration is found to have larger degradation in constant current compared with pulse current than that with lower phosphor concentration. In addition, the junction temperatures of phosphor converted white LEDs raise with increasing phosphor concentration, so that the decreased phosphor conversion efficiency is observed both in pulse and constant current modes. The physical mechanisms for these observations are discussed. This study elucidates the phosphor dependent optical and thermal behavior of phosphor converted white LEDs.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 5

Phosphor conversion efficiency versus junction temperature of white LEDs driven at the current from 50 mA to 600 mA under constant current modes

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Figure 4

Phosphor conversion efficiency of white LEDs driven from 50 mA to 600 mA with different phosphor concentration of 4 wt %, 8 wt %, and 13 wt %, respectively

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Figure 3

Junction temperatures of LEDs with different phosphor concentration driven at the current from 50 mA to 600 mA in the same ambiance

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Figure 2

Relative radiation power and lumen output of LEDs under the constant current mode with respect to the pulse current mode at the current level from 50 mA to 600 mA

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Figure 1

Schematic cross-sectional view of the white LED package

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