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This paper brings a brief review of LED parameters that can be changed during the life of these types of light sources. Firstly the change of quantitative parameter of emitted light is presented (luminous flux) and following part is dedicated to change of quality parameter (spectral distribution) and change of electrical parameters. Modification of these parameters may affect the use of LEDs in lighting...
The degradation of high power GaN-based blue light-emitting diodes (LEDs) was investigated by considering the electrical, optical and electroluminescence spectrum aging characteristics. The LED samples are stressed at the condition of 85°C and 85% RH using an injection current of 1000 mA. Optical output power decreases to 80% of initial value after 1000 hours of temperature/humidity accelerated tests...
Life models relate the time to failure to the applied stress. They can be derived starting from knowledge of chemical/physical phenomena involved in the ageing process caused by the stress or by means of regressive techniques on data acquired in ALT-based procedure. Anyway, experimental tests are needed. This paper deals with a test system implemented to estimate a life model for LEDs where the forward...
In reliability analysis, engineers lacks confidence to verify the mean time to failure of high power light emitting diodes from aging or degradation tests. The lifetime information, however, is important to manufacturers to improve the quality of light emitting diodes. The paper provides a bootstrap computation procedure to infer the mean time to failure of high power light emitting diodes. Assume...
In this study, we have investigated the high-temperature electro-optical degradation of DC-Aged InGaN based high power GaN LEDs. For this purpose, we fabricated large size blue InGaN/GaN LED chips (1mm??1mm) by using standard LED fabrication processes, where the ITO and Cr/Au served as p-type ohmic contact and n-ohmic contact layer, respectively.
This paper describes an analysis of the reliability of AlGaN-based deep-UV Light-Emitting Diodes (LEDs) emitting in the range 280-340 nm. LEDs have been aged at their nominal operating current, and during treatment their electrical and optical characteristics have been continuously monitored. Measurement results show that (i) constant current stress can induce degradation of the optical power emitted...
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