Synthesis and photoluminescence properties of Eu2+ doped CaS and SrS phosphor for phosphor converted white light emitting diodes

Game, D. N.; Ingale, N.B.; Omanwar, S. K.

doi:10.1007/s10854-016-5607-x

Cited by 7 publications

(4 citation statements)

References 22 publications

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“…Note that while the three phosphors (SAED, and ) have Eu 2+ ion as the emitter, different PL excitation and emission spectra are realized since the 4f 7 ( 8 S 7/2 ) → 4f 6 5d 1 transition of the Eu 2+ emitter is strongly affected by the crystal field strength and host material 42 , 43 . The x-ray patterns showing that the phosphors were polycrystalline are also provided in Supplementary Figs.…”

Section: Resultsmentioning

confidence: 99%

Dual-color dynamic anti-counterfeiting labels with persistent emission after visible excitation allowing smartphone authentication

Katumo

Richards

et al. 2022

Sci Rep

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A significant impediment to the deployment of anti-counterfeiting technologies is the reliance on specialized hardware. Here, anti-counterfeiting labels are developed that are both excited and detected using a smartphone. The persistent luminescence pattern and color changes on the timescale of hundreds of milliseconds to seconds. The labels can be authenticated by comparing still images from the red and green channels of video acquired at known times after flashlight excitation against expected reference patterns. The labels are based on a green-emitting SrAl2O4: Eu2+,Dy3+ (SAED), and red-emitting CaS:Eu2+ phosphors whose lifetimes are varied: (i) for SAED from 0.5 to 11.7 s by annealing the commercial material in air; and (ii) CaS:Eu2+ from 0.1 to 0.6 s by varying the dopant concentration. Examples of anti-counterfeiting labels exhibiting changing emission patterns and colors on a seven-segment display, barcode, and emoji are demonstrated. These results demonstrate that phosphors with visible absorption and tunable persistent luminescence lifetimes on the order of hundreds of milliseconds to seconds are attractive for anti-counterfeiting applications as they allow authentication to be performed using only a smartphone. Further development should allow richer color shifts and enhancement of security by embedding further covert anti-counterfeiting features.

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Section: Resultsmentioning

confidence: 99%

Dual-color dynamic anti-counterfeiting labels with persistent emission after visible excitation allowing smartphone authentication

Katumo

Richards

et al. 2022

Sci Rep

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“…The concept of separating the chip and the phosphor layer of remote phosphor structures has been demonstrated in previous studies [7][8][9][10][11][12]. As can be seen, the enhanced light extraction internal reflection structure which uses a polymer hemispherical shell lens with an interior phosphor coating is known as an effective tool to increase extraction efficiency [13].…”

Section: Introductionmentioning

confidence: 95%

The impacts of Ba₂Li₂Si₂O₇:Sn²⁺,Mn²⁺ and CaMgSi₂O₆:Eu²⁺,Mn²⁺ particles on the optical properties of remote phosphor LED

Chen¹,

Loan²,

Tho

et al. 2020

Materials Science-Poland

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As implied in the title, the triple-layer remote phosphor (TRP), constructed with the yellow YAG:Ce3+ layer at the bottom, the red CaMgSi2O6:Eu2+,Mn2+ phosphor layer on the top, and the green Ba2Li2Si2O7:Sn2+,Mn2+ phosphor layer between these two layers, is suggested in this paper to improve the color and luminescence of white LEDs (WLEDs). In order to control the red light for the purpose of increasing the color rendering index (CRI), it is suggested that the red CaMgSi2O6:Eu2+,Mn2+ phosphor should be applied in the TRP structure. Simultaneously, the structure uses the green Ba2Li2Si2O7:Sn2+,Mn2+ phosphor layer to control the green light, which increases the luminous efficacy (LE) of WLEDs. In addition, when the concentration of these two phosphors increases, the yellow YAG:Ce3+ concentration must be reduced to keep the average correlated color temperatures (ACCTs) stable at 6000 K to 8500 K. Besides, appropriate adjusting of CRI, LE, and color quality scale (CQS) is also analyzed by modifying the concentration of the green phosphor and red phosphor. The results show that the CRI can get better values if CaMgSi2O6:Eu2+,Mn2+ concentration is higher. In contrast, the CRI decreases dramatically when the concentration of Ba2Li2Si2O7:Sn2+,Mn2+ increases. Meanwhile, CQS can be significantly increased in the range of 10 % to 14 % CaMgSi2O6:Eu2+,Mn2+, regardless of the concentration of Ba2Li2Si2O7:Sn2+,Mn2+. In particular, along with the improvement of CRI and CQS, LE can also be increased by more than 40 % by reducing the scattered light and adding the green light. Obtained results are a valuable reference for manufacturers for improving WLEDs color and luminescence quality to produce a broader range of WLEDs with better quality fulfilling social needs.

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“…One of the most common methods for white light generation is the combination of yellow rays converted from the red phosphors and the blue rays from the LED chip [6][7][8]. Although this concept might be recognizable, it must be accepted that the packaging design of LEDs and the organization of phosphor layers are vital to effectively determine the luminous efficiency, especially the color rendering index (CRI) [9][10][11]. Scientists have proposed several familiar phosphor coating methods for pc-LED fabrication such as conformal and dispensing 668 PHUNG TON THAT et al…”

Section: Introductionmentioning

confidence: 99%

Enhancing color quality of WLEDs with dual-layer remote phosphor geometry

That

Loan²,

Tho

et al. 2020

Materials Science-Poland

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Usually, remote phosphor structures are beneficial in terms of flux but unfavorable in terms of color quality compared to conformal phosphor or in-cup phosphor packages. To eliminate this disadvantage, many studies have focused on increasing the chromatic quality of the remote phosphor configuration, which requires great efforts in improving two parameters of color: color rendering index (CRI) and color quality scale (CQS). CRI is known as the most useful quantitative method used to measure the ability of a light source to reproduce the colors of illuminated objects faithfully and naturally. Similarly, CQS is also a method of lighting quality determination and analysis, especially used as an alternative to the unsaturated CRI colors. In this paper, we proposed dual-layer remote phosphor structure as a novel method of CRI and CQS enhancement to improve WLEDs’ color quality. Five alike WLEDs but having different color temperatures in the range of 5600 K to 8500 K were applied in this study. The idea behind the study is to place a red phosphor layer SrwFxByOz:Eu2+,Sm2+ on the yellow phosphor layer YAG:Ce3+ and then determining an appropriate concentration of SrwFxByOz:Eu2+,Sm2+ added to achieve the highest color quality. The results point out that SrwFxByOz:Eu2+,Sm2+ brings great benefits to the improvement of CRI and CQS parameters. Specifically, the higher the SrwFxByOz:Eu2+,Sm2+ concentration results in the greater CRI and CQS, owning to the enriched red light components in the WLEDs. However, the flux has a tendency of dropping when SrwFxByOz:Eu2+,Sm2+ concentration rises excessively. This has been proved by using the Mie-scattering theory and the Lambert-Beer law. The results of this article are essential references for manufacturing WLEDs with higher chromatic quality.

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Synthesis and photoluminescence properties of Eu2+ doped CaS and SrS phosphor for phosphor converted white light emitting diodes

Cited by 7 publications

References 22 publications

Dual-color dynamic anti-counterfeiting labels with persistent emission after visible excitation allowing smartphone authentication

Dual-color dynamic anti-counterfeiting labels with persistent emission after visible excitation allowing smartphone authentication

The impacts of Ba₂Li₂Si₂O₇:Sn²⁺,Mn²⁺ and CaMgSi₂O₆:Eu²⁺,Mn²⁺ particles on the optical properties of remote phosphor LED

Enhancing color quality of WLEDs with dual-layer remote phosphor geometry

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Synthesis and photoluminescence properties of Eu2+ doped CaS and SrS phosphor for phosphor converted white light emitting diodes

Cited by 7 publications

References 22 publications

Dual-color dynamic anti-counterfeiting labels with persistent emission after visible excitation allowing smartphone authentication

Dual-color dynamic anti-counterfeiting labels with persistent emission after visible excitation allowing smartphone authentication

The impacts of Ba2Li2Si2O7:Sn2+,Mn2+ and CaMgSi2O6:Eu2+,Mn2+ particles on the optical properties of remote phosphor LED

Enhancing color quality of WLEDs with dual-layer remote phosphor geometry

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The impacts of Ba₂Li₂Si₂O₇:Sn²⁺,Mn²⁺ and CaMgSi₂O₆:Eu²⁺,Mn²⁺ particles on the optical properties of remote phosphor LED