Color Shift Investigations for LED Secondary Optical Designs: Comparison between BPA-PC and PMMA

Lu, Guangjun; Mehr, M. Yazdan; Driel, W.D. van; Fan, Xuejun; Fan, Jiajie; Jansen, K.M.B.; Zhang, G.Q.

doi:10.1016/j.optmat.2015.03.005

Cited by 45 publications

(32 citation statements)

References 17 publications

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“…Depending on the design of the device, yellowing of both lenses and reflectors can alter the emission spectrum from the SSL device; however, changes in the lens usually have a much greater impact than changes in the reflector surrounding the LED packages. 13,15 The optical effects are discussed in Section 1.2 of this report.…”

Section: Chromaticity Shifts In Led Packages and Modulesmentioning

confidence: 99%

“…The optical materials that are commonly used in LED devices may change over time, and some common materials are more subject to change than others. 14 These changes often occur over long periods of time with an incubation period that may last hundreds of hours, 15 followed by a prolonged period of a nearly linear rate of change that has a strong wavelength dependence. 13 Figure 1-4 shows the expected change in transmittance of polycarbonate lens after exposure to 3,000 hours (hrs) of an accelerated stress testing (AST) environment conducted at 65 degrees Celsius (°C) and 90% relative humidity (RH).…”

Section: Optical Impacts On Chromaticity Shiftsmentioning

confidence: 99%

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Accelerated Stress Testing of Multi-Source LED Products: Horticulture Lamps and Tunable-White Modules

Davis

Rountree

Mills

2018

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Solid-state lighting (SSL) technologies are bringing new capabilities to lighting products, and the growth in added functionality is driven in part by the capabilities of light-emitting diodes (LEDs). A wide variety of LED structures is readily available in a range of package sizes, luminous flux levels, emission spectra, and costs. Although these LEDs can be easily packaged together on a printed circuit board to form LED sources that are multi-functional and multi-component by using conventional electronics manufacturing technologies, the long-term performance of such systems has not been fully investigated. For example, it is unclear how differences in luminous flux and chromaticity maintenance of a product incorporating two different types of LEDs would compare with a conventional SSL product containing only a single LED type.

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Section: Chromaticity Shifts In Led Packages and Modulesmentioning

confidence: 99%

Section: Optical Impacts On Chromaticity Shiftsmentioning

confidence: 99%

Accelerated Stress Testing of Multi-Source LED Products: Horticulture Lamps and Tunable-White Modules

Davis

Rountree

Mills

2018

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“…Furthermore, this has been achieved while significantly increasing the efficiency of the device (ca. 130 lm/W) as a result of the high transmittance and light-guiding features of PMMA 50 .…”

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confidence: 99%

Long-living and highly efficient bio-hybrid light-emitting diodes with zero-thermal-quenching biophosphors

et al. 2020

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Bio-hybrid light-emitting diodes (Bio-HLEDs) based on color down-converting filters with fluorescent proteins (FPs) have achieved moderate efficiencies (50 lm/W) and stabilities (300 h) due to both thermal-and photo-degradation. Here, we present a significant enhancement in efficiency (~130 lm/W) and stability (>150 days) using a zero-thermalquenching bio-phosphor design. This is achieved shielding the FP surface with a hydrophilic polymer allowing their homogenous integration into the network of a light-guiding and hydrophobic host polymer. We rationalize how the control of the mechanical and optical features of this bio-phosphor is paramount towards highly stable and efficient Bio-HLEDs, regardless of the operation conditions. This is validated by the relationships between the stiffness of the FP-polymer phosphor and the maximum temperature reached under device operation as well as the transmittance of the filters and device efficiency.

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“…The selection of this material has also been based on the analysis of the rest of their properties, which allowed optimizing multiple technical criteria and to lighting applications (this material has very slight optical variations with solar radiation and temperature changes [27]), mechanical, economic, and ecological factors [28,29]. As a basic specification, the three covers are required to have a good degree of protection against impact, equal to or greater that IK10, which offers the maximum guarantees of safety and protection of the equipment.…”

Section: Description Of the Tested Optic Covers For Luminairesmentioning

confidence: 99%

Evaluation of Uniformity and Glare Improvement with Low Energy Efficiency Losses in Street Lighting LED Luminaires Using Laser-Sintered Polyamide-Based Diffuse Covers

et al. 2018

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Energy saving in street lighting is garnering more interest and has become a priority in municipal management. Therefore, LED luminaires are gradually becoming prevalent in our cities. Beyond their energy/economic saving potential, quality in public lighting installations concerns aspects such as uniformity and glare which must be maintained if not improved in any installation renewal project using this technology. The high light intensity generated in a discrete point in LED packages and its directional nature result in significant deficiencies in these last two parameters. To soften these effects, translucent covers are being used as one of the most common solutions with the drawback of significant light intensity losses. The objective of this paper is to evaluate the behavior of LED luminaire's polyamide-based optical covers manufactured with a laser-sintered process. These are designed to improve glare and uniformity output, to minimize light output reductions, and to be industrially manufactured with no increment of cost for their lighting equipment compared to conventional transparent polycarbonate solutions. A laboratory and field lighting test study has been applied to different covers with the same LED lamp and luminaire to compare the performance of three different solutions built with different polymeric materials and with different light transmission surface textures. The photometric results have been observed and discussed to demonstrate the ability to significantly improve the lighting performance of LED luminaires-illuminance and uniformity levels and discomfort and disability glare indexes-using an improved optic cover.

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Color Shift Investigations for LED Secondary Optical Designs: Comparison between BPA-PC and PMMA

Cited by 45 publications

References 17 publications

Accelerated Stress Testing of Multi-Source LED Products: Horticulture Lamps and Tunable-White Modules

Accelerated Stress Testing of Multi-Source LED Products: Horticulture Lamps and Tunable-White Modules

Long-living and highly efficient bio-hybrid light-emitting diodes with zero-thermal-quenching biophosphors

Evaluation of Uniformity and Glare Improvement with Low Energy Efficiency Losses in Street Lighting LED Luminaires Using Laser-Sintered Polyamide-Based Diffuse Covers

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