scholarly journals Review of Low-Frequency Noise Properties of High-Power White LEDs during Long-Term Aging

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 13
Author(s):  
Vilius Palenskis ◽  
Jonas Matukas ◽  
Justinas Glemža ◽  
Sandra Pralgauskaitė
Keyword(s):  
Output Power ◽  
Blue Light ◽  
White Light ◽  
High Power ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Phosphor Layer ◽  
Light Emitting

Low-frequency noise investigation is a highly sensitive and very informative method for characterization of white nitride-based light-emitting diodes (LEDs) as well as for the evaluation of their degradation. We present a review of quality and reliability investigations of high-power (1 W and 3 W) white light-emitting diodes during long-term aging at the maximum permissible forward current at room temperature. The research was centered on the investigation of blue InGaN and AlInGaN quantum wells (QWs) LEDs covered by a YAG:Ce3+ phosphor layer for white light emission. The current-voltage, light output power, and low-frequency noise characteristics were measured. A broadband silicon photodetector and two-color (blue and red) selective silicon photodetectors were used for the LED output power detection, which makes it possible to separate physical processes related to the initial blue light radiation and the phosphor luminescence. Particular attention was paid to the measurement and interpretation of the simultaneous cross-correlation coefficient between electrical and optical fluctuations. The presented method enables to determine which part of fluctuations originates in the quantum well layer of the LED. The technique using the two-color selective photodetector enables investigation of changes in the noise properties of the main blue light source and the phosphor layer during the long-term aging.

scholarly journals Low-frequency noise characteristics of high-power white LED during long-term aging experiment

2018 ◽  
Vol 58 (2) ◽  
Author(s):  
Justinas Glemža ◽  
Jonas Matukas ◽  
Sandra Pralgauskaitė ◽  
Vilius Palenskis
Keyword(s):  
High Power ◽  
Cross Correlation ◽  
Light Output ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Phosphor Layer ◽  
Noise Characteristics ◽  
The Cross

Low-frequency electrical and optical noise characteristics of a high power white InGaN LED and the cross-correlation coefficient between these fluctuations are investigated during the long-term ageing experiment (28000 h). The analysis of cross-correlation shows that the correlated part of the low-frequency electrical noise, which indicates physical processes in the active area of the LED, varies during the ageing experiment. Two main stages are distinguished considering the rapid changes of the noise characteristics. The initial stage (after the first 1100 h) is followed by the decrease in the noise power at low forward currents and the increase in the light output. The final stage (after 28000 h) is characterized by a strong growth of the low-frequency noise, the decrease of the light output and the increase of the correlated part of electrical and optical fluctuations. These changes mean a failure in the active layer of the LED. The optical output decomposition into two spectral parts, the radiation generated by the LED chip and the radiation generated by the phosphor layer, enables evaluation of the phosphor layer influence on the degradation process of device optical characteristics. Despite the fact that this layer contributes to the variation of the LED chromatic properties, the cross-correlation analysis has shown that the phosphor layer does not act as a possible noise source during the ageing experiment.

Correlation between forward-reverse low-frequency noise and atypical I–V signatures in 980 nm high-power laser diodes

2015 ◽  
Vol 55 (9-10) ◽  
pp. 1741-1745 ◽  
Author(s):  
P. Del Vecchio ◽  
A. Curutchet ◽  
Y. Deshayes ◽  
M. Bettiati ◽  
F. Laruelle ◽  
...  
Keyword(s):  
High Power ◽  
Laser Diodes ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
High Power Laser ◽  
Power Laser

Reliability investigation of light-emitting diodes via low frequency noise characteristics

2015 ◽  
Vol 55 (1) ◽  
pp. 52-61 ◽  
Author(s):  
Sandra Pralgauskaitė ◽  
Vilius Palenskis ◽  
Jonas Matukas ◽  
Justinas Glemža ◽  
Grigorij Muliuk ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Light Emitting ◽  
Noise Characteristics

Low-frequency noise of GaN-based ultraviolet light-emitting diodes

2005 ◽  
Vol 97 (12) ◽  
pp. 123107 ◽  
Author(s):  
S. L. Rumyantsev ◽  
S. Sawyer ◽  
M. S. Shur ◽  
N. Pala ◽  
Yu. Bilenko ◽  
...  
Keyword(s):  
Ultraviolet Light ◽  
Light Emitting Diodes ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Light Emitting ◽  
Ultraviolet Light Emitting Diodes

Cylindrical Tuber Encapsulant Layer Realization by Patterned Surface for Chip-on-Board Light-Emitting Diodes Packaging

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Xingjian Yu ◽  
Run Hu ◽  
Ruikang Wu ◽  
Bin Xie ◽  
Xiaoyu Zhang ◽  
...  
Keyword(s):  
Blue Light ◽  
White Light ◽  
Light Emitting Diodes ◽  
Composite Layer ◽  
Color Temperature ◽  
Efficiency Enhancement ◽  
Phosphor Layer ◽  
Light Emitting ◽  
Nanosilica Particles ◽  
Light Efficiency

In this study, we realized a cylindrical tuber silicone layer for improving the light efficiency of chip-on-board light-emitting diodes (COB-LEDs) by fabricating patterned LED substrate with both silicone-wetting and silicone-repellency surfaces. To realize silicone-repellency surface, low surface energy modified nanosilica particles were prepared and deposited on the LED substrate to form porous hierarchical structure. Light efficiency enhancement for blue light COB-LEDs with pure cylindrical tuber silicone layer and white light COB-LEDs with phosphor–silicone composite layer was studied. The results show that for blue light COB-LEDs with pure cylindrical tuber silicone layer, the light efficiency increases with the contact angle and a highest light efficiency enhancement of 62.6% was achieved at 90 deg when compared to the flat silicone layer. For white light COB-LEDs at correlated color temperature (CCT) of ∼5500 K, the cylindrical tuber silicone layer enhances the light efficiency by 13.6% when compared to the conventional flat phosphor layer.

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