Solid-state lighting: failure analysis of white LEDs

Reliability and Lifetime Prediction of Remote Phosphor Plates in Solid-State Lighting Applications Using Accelerated Degradation Testing

“…[1][2][3][4] It has been already shown that thermal stress degrades the luminous output of the devices. [15][16][17][18][19][20][21][22][23] This study aims at studying the effect of blue light intensity together with thermal stress on the lumen depreciation and the reliability of LED-based products and on the acceleration of optical degradation. The phosphor layer can itself be a heat generator as the input power increases and becomes more important if there is not a sufficient thermal path for heat dissipation.…”

“…[1][2][3][4][5][6][7][8][9][10] In this type of LED, the phosphor is either coated on the chip or mixed with the lens disc. [11][12][13][14][15][16][17][18][19][20][21][22] The spatial distribution of phosphor in white LED lamps strongly influences the colour uniformity and the efficiency of the light source. In proximate phosphor distributions, the phosphor is located in close proximity to the semiconductor chip, while in the remote phosphor configuration, there is a distance between the phosphor layer and the chip.…”

“…Application of both thermal stress and light intensity in a HAST set-up is expected to make the kinetics of degradation much faster. There are many papers regarding the reliability of LED systems [13][14][15][16][17][18][19][20][21] under thermal stress; however, there is limited information available about the effects of combined blue light intensity and thermal stress on the ageing and the reliability of remote phosphors. In this study, the effects of both stress factors, applied in the HAST set-up, are studied.…”

Effects of Graphene Monolayer Coating on the Optical Performance of Remote Phosphors

“…In such a system, the phosphor layer can be either deposited directly on the chip or incorporated into a lens disk. [9][10][11][12][13] Moreover, white LEDs are multipart systems. Apparently, each of these components can break and induce failure, leading to a reduction of light intensity and even early failure before the expected lifetime of the instrument.…”

Performance of LED street lights in hot environments

“…With the use of large LED arrays, it is possible to generate a large heat loads at the system level which can cause challenges for overall heat dissipation, especially when passive cooling is used. The large array with passive cooling techniques leads to elevated LED die temperatures, which have been linked to lower quantum efficiencies, shorter lifetimes, emission wavelength shifts and, catastrophic device failure [1][2][3][4][5][6]. A heat flux from a 900 high brightness LED chip, has already reached approximately 125 / [3] which is considered relatively high heat flux and comparable to heat generation in integrated circuits.…”