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

Mehr, M. Yazdan; Driel, W.D. van; Zhang, G.Q.

doi:10.1007/s11664-015-4120-y

Cited by 27 publications

(18 citation statements)

References 18 publications

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“…At the same time, browning of the phosphor-encapsulating material also takes place. While all these factors contribute to the LED light output degradation, their rate of kinetics differs [5]. During ageing, these rates vary, so this affects chromatic properties of the device differently.…”

Section: Changes Of Optical Characteristics Influenced By the Phosphomentioning

confidence: 99%

“…While most standards of the LED industry for lifetime assessment are based on lumen maintenance [5], investigation of electrical characteristics is not less important [3]. Various processes, like growth of non-radiative recombination, instabilities of dopants or impurities, increase of thermal resistance, etc., accelerate GaN-based optoelectronic device degradation and lower performance [2].…”

Section: Introductionmentioning

confidence: 99%

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

Glemža¹,

Matukas²,

Pralgauskaitė³

et al. 2018

physics

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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.

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Section: Changes Of Optical Characteristics Influenced By the Phosphomentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Glemža¹,

Matukas²,

Pralgauskaitė³

et al. 2018

physics

View full text Add to dashboard Cite

show abstract

“…The efficiency of state-of-the-art light emitting phosphors, such as doped yttrium-aluminum-garnet, is mainly determined by two types of energy losses, the stokes shift (~80% efficiency) and the photoluminescence quantum yield (~90%) 10 . Both these loss mechanisms scale with temperature 10 (e.g., as a result of illumination) and therefore phosphor luminescence suffers from saturation 10 , aging 11 , and thermal quenching 10 , limiting the irradiance tõ 5 kW cm −2 and thus the overall light output. Even though new concepts such as glass encapsulation 12,13 , phosphor monoliths 14 , or composite ceramic phosphors [15][16][17] can increase the irradiance level up to~10-20 kW cm −2 , the true potential of lasers for highbrightness lighting applications, with possible light outputs of several MW cm −2 , still remains unemployed.…”

mentioning

confidence: 99%

Conversionless efficient and broadband laser light diffusers for high brightness illumination applications

et al. 2020

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Laser diodes are efficient light sources. However, state-of-the-art laser diode-based lighting systems rely on light-converting inorganic phosphor materials, which strongly limit the efficiency and lifetime, as well as achievable light output due to energy losses, saturation, thermal degradation, and low irradiance levels. Here, we demonstrate a macroscopically expanded, three-dimensional diffuser composed of interconnected hollow hexagonal boron nitride microtubes with nanoscopic wall-thickness, acting as an artificial solid fog, capable of withstanding~10 times the irradiance level of remote phosphors. In contrast to phosphors, no light conversion is required as the diffuser relies solely on strong broadband (full visible range) lossless multiple light scattering events, enabled by a highly porous (>99.99%) nonabsorbing nanoarchitecture, resulting in efficiencies of~98%. This can unleash the potential of lasers for high-brightness lighting applications, such as automotive headlights, projection technology or lighting for large spaces.

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“…A lot of research has been done to model the light output degradation of LED-based products and LED packages [7,8,9,10]. In addition to lumen maintenance, colour shift over service time is another concern for LED manufacturers [11,12,13,14,15,16,17,18]. Both colour shift and lumen depreciation normally take place with relatively slow kinetics.…”

Section: Introductionmentioning

confidence: 99%

Study on the Degradation of Optical Silicone Exposed to Harsh Environments

et al. 2018

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Degradation mechanisms of silicone plates under harsh environment conditions are studied in this investigation. Environmental degradation of silicone free form, used as secondary optics in Light Emitting Diode LED lighting lamps and luminaires or any other applications requiring high quality optics being used, has negative implications for the optical performance. Degradation of silicone plates in harsh environment conditions was studied in salt bath and swimming water environments, using different light radiation and temperatures. Samples were exposed to harsh environment conditions for up to 4 months. Optical and chemical characteristics of exposed plates were studied using an Fourier transform infrared- attenuated total reflection FTIR-ATR spectrometer, an integrated sphere, and a Lambda 950 Ultraviolet-Visible UV-VIS spectrophotometer. Results show that 100 °C salt bath exposure had the most severe degrading effect on the optical characteristic of silicone plates. Increasing exposure time in the salt bath at that high temperature is associated with a significant deterioration of both optical (i.e., light transmission and relative radiant power value) and mechanical properties of silicone samples. On the contrary, silicone plates showed a great degree of stability against light exposure (UV at 360 nm and blue light at 450 nm).

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

Cited by 27 publications

References 18 publications

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

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

Conversionless efficient and broadband laser light diffusers for high brightness illumination applications

Study on the Degradation of Optical Silicone Exposed to Harsh Environments

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