Improvement of emission efficiency and color rendering of high-power LED by controlling size of phosphor particles and utilization of different phosphors

Chen, Lei; Chu, Cheng-I; Liu, Ru‐Shi

doi:10.1016/j.microrel.2011.07.058

Cited by 39 publications

(13 citation statements)

References 18 publications

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“…But, the separated driving circuits for each LED are costly. Moreover, the efficiency of the green LED, known as “green gap”, is much lower than that of red and blue ones. ,, In contrast, phosphor-converted (pc) white LED backlights, which combine a single LED chip with phosphor materials, are extensively adopted due to their high efficiency and low cost. In pc-wLED backlights, the three key technical parameters, namely, color gamut, luminous efficacy, and reliability, are dominantly determined by phosphor materials. − In general, phosphors for backlights are required to have a narrow emission band and a specific peak position, high quantum efficiency, and excellent thermal stability. , To develop backlighting technology capable of displaying bright and vivid images, innovative phosphor materials with narrow-band emissions in the green and red spectral regions are continuously pursed. ,,− Since human eyes are highly sensitive to green light, the development of efficient narrow-band green phosphors seems to be particularly crucial to increase the maximum accessible color gamut and luminous efficacy. , …”

Section: Introductionmentioning

confidence: 99%

Achieving High Quantum Efficiency Narrow-Band β-Sialon:Eu²⁺ Phosphors for High-Brightness LCD Backlights by Reducing the Eu³⁺ Luminescence Killer

et al. 2017

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β-Sialon:Eu2+ has been reported to be the most promising narrow-band green phosphor for wide color gamut LCD backlights, but the coexistence of the Eu3+ luminescence killer with the Eu2+ luminescence center limits its luminescence performance to a great extent. In this study, we propose a direct reduction strategy to successfully realize the reduction of Eu3+ to Eu2+ and, finally, increase the effective concentration of Eu2+ in the crystal lattice and greatly minimize the amount of Eu3+ on the particle surface. As a result, the luminescence of treated β-sialon:Eu2+ is enhanced by 2.3 times, and the internal quantum efficiency significantly increases from 52.2 to 96.5%. The mechanisms for such large enhancements in luminescence are clarified by investigating the microstructure, luminescence spectra, valence state, concentration, and distribution of Eu using a variety of chemical analyses. We find that the low efficiency is ascribed to the coexistence of the Eu3+ luminescence killer with the Eu2+ luminescence center. The white LED backlight using the treated β-sialon:Eu2+ demonstrates a high luminous efficacy of 136 lm W–1 (22.5% up) and a wide color gamut (∼96% National Television System Committee standard (NTSC)), which thus promises high brightness and energy saving. We believe that the strategy proposed in this work would also work for other luminescent materials containing mixed valence of dopants.

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Section: Introductionmentioning

confidence: 99%

Achieving High Quantum Efficiency Narrow-Band β-Sialon:Eu²⁺ Phosphors for High-Brightness LCD Backlights by Reducing the Eu³⁺ Luminescence Killer

et al. 2017

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“…It is also possible to manufacture LEDs with full spectrum white emission by compounding together three phosphors that separately emit in widely separated wave length bands. 78 Such advances are enabling the new generation of high-performance LEDs with exceptional color rendering properties.…”

Section: Phosphors For White Ledsmentioning

confidence: 99%

Solid-state lighting with wide band gap semiconductors

Rahman

2014

MRS Energy & Sustainability

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Gallium nitride is currently the wide band gap semiconductor material from which almost all commercial LEDs for solid-state lighting are manufactured but in the future other promising materials, such as zinc oxide (ZnO), are also likely to play a leading role.• With further developments in LED technology, leading to cheaper luminaires, perhaps based on gallium nitride-on-silicon material, LED lamps will largely replace tungsten incandescent bulbs in the years to come. ABSTRACTLight-emitting diodes (LEDs) made from wide band gap semiconductors, such as gallium nitride, are undergoing rapid development.Solid-state lighting with these LEDs is transforming patterns of energy usage and lifestyle throughout the world.With solid-state lighting gradually taking over from incandescent and fluorescent lighting, light-emitting diodes (LEDs) are very much the focus of research nowadays. This compact review takes a look at LEDs for lighting applications made from wide band gap semiconductors.A very brief history of electric lighting is included for completeness, followed by a description of blue-emitting LEDs that serve as pump sources for all 'white' LEDs. This is followed by a discussion on techniques to extract more light from the confines of LED chips through surface patterning. The thermal management of LEDs is perhaps the most important consideration in designing and using LED-based luminaires.This topic is discussed with regard to recent studies on LED reliability. The very promising development of gallium nitride-on-silicon LEDs is examined next followed by a discussion on phosphors for color conversion in LEDs. LED lighting has positively infl uenced both upscale and downscale illumination markets worldwide. Its societal impact is examined, with the review concluding with a look at efforts to produce LEDs from zinc oxide -a material that holds much promise for the future of solid-state lighting.vacuum tube era with devices based on gas-fi lled incandescent and fl uorescent bulbs illuminating our homes and workplaces. It is only over the last two decades that solid-state light generating devices in the form of light-emitting diodes (LEDs) have become available as an alternative for lighting up living spaces. 1 , 2 This review takes a look at their development, current status, and future prospects. After a brief historical introduction, the development and structure of the blue LED at the heart of all white LEDs are examined. This is followed by a description of various techniques that have been explored to extract more light from LED chips. Such techniques make LEDs brighter without increasing their energy consumption and thus enhance their attractiveness as energy-effi cient light sources. The relatively recent development of a gallium nitride-on-silicon material for low cost, high performance LEDs is examined next, followed by a look at the phosphor technology for white LEDs.The societal impact of LED lighting is then described with this review ending by examining the still distant goal of making LEDs out of zinc ox...

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“…However, this way has some disadvantages like high cost, complicated electronic equipment, mismatched aging performance, and so on. 4 Another way is phosphor-converted WLEDs (pc-WLEDs), which is the combination of a single LED chip with one or more downconversion phosphor(s). At present, the latter is the mainstream in the consumer market.…”

Section: ■ Introductionmentioning

confidence: 99%

Luminescence and Energy Transfer of Color-Tunable Y₂Mg₂Al₂Si₂O₁₂:Eu²⁺,Ce³⁺ Phosphors

Zhang

Zheng

et al. 2021

Inorg. Chem.

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Color-tunable phosphors can be obtained through codoping strategies and energy transfer regulation. Ce 3+ and Eu 2+ are the most common and effective activator ions used in phosphor materials. However, the energy transfer from Eu 2+ to Ce 3+ is rarely reported. In this work, Y 2 Mg 2 Al 2 Si 2 O 12 (YMAS):Eu 2+ ,Ce 3+ phosphors were successfully synthesized, which was confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Rietveld refinement, scanning electron microscopy (SEM) and element mapping images, and spectral information. The luminescent color of YMAS:Eu 2+ ,Ce 3+ phosphors could be tuned from blue to cyan to light green to yellow-green and finally to green-yellow, which was achieved by adjusting the energy transfer between different dopants. The energy transfer from Eu 2+ to Ce 3+ was confirmed by photoluminescence spectra and fluorescence decay curves. Within the experimental gradient, the energy transfer efficiency could reach up to 48%. At 373 K, the Y 1.99 Mg 1.99 Al 2 Si 2 O 12 :0.01Eu 2+ ,0.01Ce 3+ (YMAS:0.01Eu 2+ ,0.01Ce 3+ ) phosphor exhibited a total integral emission loss of only 8%, and the emission peak intensity decreased to 95%, indicating the excellent thermal stability. The white light-emitting diode (WLED) fabricated by the YMAS:0.01Eu 2+ ,0.01Ce 3+ phosphor has the same level correlated color temperature (CCT = 5841 K), greatly improved color rendering index (R a = 87.8), and higher quality white light color (CIE = (0.3258, 0.3214)) than the WLED made by the YMAS:0.01Eu 2+ phosphor, indicating that the performance of the phosphor was significantly improved by introducing Ce 3+ . This work provides an effective guide for the design and development of highly efficient color-tunable phosphors involving energy transfer from Eu 2+ to Ce 3+ in some specific materials, such as garnet structures.

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Improvement of emission efficiency and color rendering of high-power LED by controlling size of phosphor particles and utilization of different phosphors

Cited by 39 publications

References 18 publications

Achieving High Quantum Efficiency Narrow-Band β-Sialon:Eu²⁺ Phosphors for High-Brightness LCD Backlights by Reducing the Eu³⁺ Luminescence Killer

Achieving High Quantum Efficiency Narrow-Band β-Sialon:Eu²⁺ Phosphors for High-Brightness LCD Backlights by Reducing the Eu³⁺ Luminescence Killer

Solid-state lighting with wide band gap semiconductors

Luminescence and Energy Transfer of Color-Tunable Y₂Mg₂Al₂Si₂O₁₂:Eu²⁺,Ce³⁺ Phosphors

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Improvement of emission efficiency and color rendering of high-power LED by controlling size of phosphor particles and utilization of different phosphors

Cited by 39 publications

References 18 publications

Achieving High Quantum Efficiency Narrow-Band β-Sialon:Eu2+ Phosphors for High-Brightness LCD Backlights by Reducing the Eu3+ Luminescence Killer

Achieving High Quantum Efficiency Narrow-Band β-Sialon:Eu2+ Phosphors for High-Brightness LCD Backlights by Reducing the Eu3+ Luminescence Killer

Solid-state lighting with wide band gap semiconductors

Luminescence and Energy Transfer of Color-Tunable Y2Mg2Al2Si2O12:Eu2+,Ce3+ Phosphors

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Product

Resources

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Achieving High Quantum Efficiency Narrow-Band β-Sialon:Eu²⁺ Phosphors for High-Brightness LCD Backlights by Reducing the Eu³⁺ Luminescence Killer

Achieving High Quantum Efficiency Narrow-Band β-Sialon:Eu²⁺ Phosphors for High-Brightness LCD Backlights by Reducing the Eu³⁺ Luminescence Killer

Luminescence and Energy Transfer of Color-Tunable Y₂Mg₂Al₂Si₂O₁₂:Eu²⁺,Ce³⁺ Phosphors