Study on the Degradation of Optical Silicone Exposed to Harsh Environments

Mehr, M. Yazdan; Driel, W.D. van; Buyl, François de; Zhang, Kouchi

doi:10.3390/ma11081305

Cited by 13 publications

(3 citation statements)

References 25 publications

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“…This has to do with the fact that optical components in LED packages have a central role in the optical performance of LED devices by controlling the emission of light from the device. In fact, any depreciation in lumen output may involve a chromaticity shift as well [161][162][163][164][165][166][167][168][169][170][171][172][173][174][175][176]. As already mentioned, an LED lamp is a complicated system, containing secondary lenses, reflective layers, and diffusers, all intended to achieve a desired light emission pattern.…”

Section: Degradation Of Optical Materialsmentioning

confidence: 99%

Degradation of optical materials in solid-state lighting systems

Mehr

Bahrami

Driel

et al. 2019

International Materials Reviews

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In this paper, degradation mechanisms of optical materials, used in the light emitting diode (LED)-based products, are reviewed. The LED lighting is one of the fastest technology shifts in human history. Lighting accounts for almost 20% of the global electrical energy use, inferring that replacement of traditional lighting sources with LEDs with higher efficiencies will have major positive implications for the global energy consumption. Organic optical materials are key components in LEDs in the sense that they control the functionality of the device and they have decisive effects on the durability and reliability of LEDs. This paper aims at describing the influences of chemical structure and service conditions on the degradation mechanisms of organic optical materials in LEDs which lead to the lumen depreciation, discolouration, and colour shift of the LED light output. The contributions of different degradation mechanisms of optical and package materials in LED-based products to the lumen depreciation and colour shift are methodically reviewed.

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Section: Degradation Of Optical Materialsmentioning

confidence: 99%

Degradation of optical materials in solid-state lighting systems

Mehr

Bahrami

Driel

et al. 2019

International Materials Reviews

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“…Silicones are known for many unusual properties, compared to organic polymers, including resistance to oxidation . As a result, they are preferentially used in oxidative environments, including sealing rings for UV lamps, thermally stable elements in light-emitting diodes (LEDs), etc . Silicone foams are attractive alternatives to less expensive organic foams because of their resistance to combustion, an extreme form of oxidation.…”

Section: Introductionmentioning

confidence: 99%

Elastomeric Silicone Sponges for Bleach Delivery

Zheng

Brook

2021

ACS Appl. Polym. Mater.

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Topical disinfection protocols to inactivate organisms, particularly on high contact surfaces, have become increasingly important. A classical oxidative agent, sodium hypochlorite (bleach), has many benefits, but can be problematic during applications because of its ability to oxidize the organic polymers in which it is contained. We demonstrate that bleach-containing elastomeric sponges are readily created in one step at room temperature from thiopropyl-modified silicone oils; sodium hypochlorite induces disulfide cross-linking and a foam structure due, in part, to the concomitant formation of sulfonates. No surfactants are required. The morphology of the bleach-containing silicone sponge is tunable by the aqueous bleach solution concentration and the water/silicone ratio used. The resulting silicone sponge contains excess bleach that can be released gradually, as shown by its ability to oxidize organic molecules in aqueous solution, either directly or after dehydration/rehydration; the latter process provides a way to store the bleach-containing material in dry form. Such foams exhibit enhanced sustainability as, we show, they can be converted back to thiopropylsilicone oils by reduction using hydrosilicones. The resulting oils can be re-cross-linked, completing the life cycle.

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“…Thus, silicones have been commonly adopted for encapsulation because of advantages, including high transmittance, thermal resistance, low moisture absorption, and low modulus. [5][6][7][8][9][10][11][12][13][14][15][16] However, silicones suffer from delamination and cracking after long-term operation (or in harsh conditions 17 ), leading to the degradation of the UV-LED packages. It was reported that modification of the composition of silicones could effectively improve their performance and characteristics.…”

mentioning

confidence: 99%

Effects of Ultraviolet Wavelength and Ambient Temperature on Reliability of Silicones in InAlGaN-Based Light-Emitting-Diode Package

Kim

Lee

Jun

et al. 2020

ECS J. Solid State Sci. Technol.

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We investigated the effects of different ultraviolet wavelengths and ambient temperatures on the optical and thermal performance of light-emitting-diode packages. After application of 500 mA at 85 °C for 1500 h, the 365 nm package sample showed a larger reduction (29.2%) in the output power than the 405 nm sample (5.3%). Further, operation at 1500 mA caused a considerably large reduction of 27.2%–60.0% of the output power of the samples. After operating at 85 °C under 1500 mA for 1500 h, the thermal resistance between the junction chip and package increased to values in the range of 1.42–2.54 K W−1 depending on the peak wavelengths. The surface temperature of the 365 nm sample increased to 101.8 °C when operated at 85 °C under 500 mA for 1500 h. The thermomechanical stress was concentrated on the chip surface and measured as 3.32 MPa at 125 °C. Cracks were observed to initiate on the chip surface and propagate into the silicone lens via thermal stress. The reduction of light output power was attributed to the lowered extraction due to the occurrence of cracks, thereby decreasing the view angle and reducing the uniformity of illuminance.

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Study on the Degradation of Optical Silicone Exposed to Harsh Environments

Cited by 13 publications

References 25 publications

Degradation of optical materials in solid-state lighting systems

Degradation of optical materials in solid-state lighting systems

Elastomeric Silicone Sponges for Bleach Delivery

Effects of Ultraviolet Wavelength and Ambient Temperature on Reliability of Silicones in InAlGaN-Based Light-Emitting-Diode Package

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