DocumentCode :
29673
Title :
Thermal-Stability Comparison of Glass- and Silicone-Based High-Power Phosphor-Converted White-Light-Emitting Diodes Under Thermal Aging
Author :
Chun-Chin Tsai ; Wei-Chih Cheng ; Jin-Kai Chang ; Shun-Yuan Huang ; Jyun-Sian Liou ; Gi-Hung Chen ; Yi-Chung Huang ; Jau-Sheng Wang ; Wood-Hi Cheng
Author_Institution :
Dept. of Photonics, Nat. Sun Yat-sen Univ., Kaohsiung, Taiwan
Volume :
14
Issue :
1
fYear :
2014
fDate :
Mar-14
Firstpage :
4
Lastpage :
8
Abstract :
The lumen degradation, chromaticity shift, transmittance loss, and mean-time-to-failure (MTTF) evaluation in glass- and silicone-based high-power phosphor-converted white-light-emitting diodes (LEDs) (PC-WLEDs) under accelerated thermal aging at 150 °C, 200 °C, and 250 °C are presented and compared. The silicone-based PC-WLEDs exhibited less thermal stability than the glass-based PC-WLEDs by 1.86, 2.79, and 4.76 times higher lumen losses, 3.05, 3.26, and 6.84 times larger chromaticity shifts, and 1.82, 2.62, and 6.67 times greater transmittance losses at 150 °C, 200 °C, and 250 °C, respectively. The results also showed that the glass-based PC-WLEDs exhibited higher MTTF than the silicone-based PC-WLEDs by 20 times at room temperature. The peaks of the emission and excitation spectra for both silicone and glass phosphors were not significantly changed after thermal aging, evidenced by fluorescence spectrophotometer analyses. This indicated that the fluorescent ability of Ce:YAG-doped phosphor materials did not change after thermal aging and the transmittance loss was corresponding to the lumen loss and chromaticity shift. The results of the lumen loss, chromaticity shift, transmittance loss, and MTTF investigations clearly demonstrated that the thermal-stability performance of the glass-based PC-WLEDs was better than that of the silicone-based PC-WLEDs. The advantage of employing doped glass encapsulation in high-power PC-WLEDs could be explained: The material property of glass transition temperature of 750 °C was higher than that of silicone transition temperature of 150 °C. A better thermal stability phosphor layer of glass as encapsulation material may be beneficial to many applications where the LED modules with high power and high reliability are demanded for use in next-generation solid-state lighting.
Keywords :
ageing; fluorescence; glass; light emitting diodes; phosphors; reliability; spectrophotometry; thermal stability; LED modules; chromaticity shift; emission spectra; encapsulation material; excitation spectra; fluorescence spectrophotometer analyses; glass transition temperature; glass-based high-power phosphor-converted white LED; light-emitting diodes; lumen loss; mean-time-to-failure evaluation; reliability; silicone transition temperature; silicone-based high-power phosphor-converted white LED; solid-state lighting; temperature 150 degC to 250 degC; temperature 293 K to 298 K; thermal aging; thermal-stability comparison; transmittance loss; Aging; Glass; Light emitting diodes; Loss measurement; Phosphors; Propagation losses; Thermal stability; Aging test; high-power light-emitting diodes (LED) modules; phosphor layer;
fLanguage :
English
Journal_Title :
Device and Materials Reliability, IEEE Transactions on
Publisher :
ieee
ISSN :
1530-4388
Type :
jour
DOI :
10.1109/TDMR.2012.2206813
Filename :
6257458
Link To Document :
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