Concentration Of Red Phosphor Research Articles

The study of convex-dual-layer remote phosphor geometry in upgrading WLEDs color rendering index

<span>The white-light light-emitting diode (LED) is a semiconductor light source that usually has one chip and one phosphor layer. Because of that simple structure, the color rendering index (CRI) is really poor. Therefore, structure with double layer of phosphor and multiple chips has been studied with the phosphorus proportions and densities in the silicone are constantly changed to find the best option to improve optical properties. In research, we use red phosphor Ca5B2SiO10:Eu3+ layer to place above the yellow phosphor one, and both of them have a convex design. Then, the experiments and measurements are carried out to figure out the effects of this red phosphor as well as the convex-double-layer remote phosphor design on the LED’s performances. The measured results reveal that the light output is enhanced significantly when using convex-dual-layer structure instead of the single-layer design. Additionally, the Ca5B2SiO10:Eu3+ concentration benefits CRI and CQS at around 6600 K and 7700 K correlated color temperature (CCT). Yet, the lumen output shows a slight decline as this red phosphor concentration surpass 26% wt. Through the experiments, it is found that a double layer of chip and double phosphorus is the best structure which could support the quality of CRI and luminous flux.</span>

The application of double-layer remote phosphor structures in increasing WLEDs color rendering index and lumen output

The remote phosphor structure often has inferior color quality but better luminous flux in than conformal or in-cup configurations. Therefore, numerous researches study remote phosphor structure for methods to enhance it chromatic quality. This study introduces the use of dual-layer remote phosphor structure in WLEDs with identical structure but at different color temperature, 6600K and 7700K, to demonstrate their effect on quality indicators. The concept is placing a green phosphor layer (Ce,Tb)MgAl11O19:Ce:Tb or a red phosphor layer MgSr3Si2O8:Eu2+,Mn2+ on the layer of yellow-emitting phosphor YAG:Ce3+ and find the suitable concentration of the additional phosphor to create the best color quality. The results showed that the increase of CRI and CQS are affected by MgSr3Si2O8:Eu2+,Mn2+, in particular, the higher the concentration of red phosphor gets the better CRI and CQS because the emitted red light in enhanced. The green phosphor layer (Ce,Tb)MgAl11O19:Ce:Tb, on the other hand, is beneficial for the luminous flux. The concentration of MgSr3Si2O8:Eu2+,Mn2+ and (Ce,Tb)MgAl11O19:Ce:Tb, however, need to be adjusted properly to avoid decreasing the luminous flux due to overgrowth. The Mie scattering theory and Beer’s law are the verification tools for these conclusions, which gives them the credibility to be applied in producing better quality WLEDs.

Green-emitting Gd<sub>2</sub>O<sub>2</sub>S:Tb<sup>3+</sup> and red-emitting Y<sub>3</sub>Al<sub>5</sub>O<sub>12</sub>:Cr<sup>3+</sup> phosphors: a suitable selection for enhancing color quality of remote phosphor structure

This article demonstrates green-emitting phosphor Gd 2 O 2 S:Tb 3+ and red-emitting phosphor Y 3 Al 5 O 12 :Cr 3+ application in the triple-layer phosphor WLED to enhance optical performance. The arrangement of phosphor layers in the WLED is red phosphor Y 3 Al 5 O 12 :Cr 3+ on top, green phosphor Gd 2 O 2 S:Tb 3+ in the middle, and yellow phosphor YAG:Ce 3+ at the bottom. The principal to utilize these phosphor materials is the exploitation of additional red light component and green light component from the green and red phosphor to enrich the color rendering index (CRI) and luminous efficacy. The influences of green phosphor and red phosphor are also estimated with a new quality indicator, the color quality index (CQS). The results show red phosphor Y 3 Al 5 O 12 :Cr 3+ enable CRI when its concentration increases while green phosphor exhibits a contrast reaction. Regarding the CQS, the optimal red phosphor concentration for CQS is from 10% to 14%, disregard the concentration in green phosphor. The improvement that applying these two phosphor materials brought comes from limiting the light loss from back-scattering and strengthen chromatic performance through addition red and green light components. These findings can support manufacturers in adapting to modern lighting requirements by improving CRI, CQS and particularly luminous efficiency to more than 40%.

Effect of Red Y2O3:Eu3+ phosphor on the color quality and luminous efficacy of the 7000K IPW-LEDs

In this study, we investigate the effect of concentration of the red Y2O3:Eu3+ phosphor on the Color Rendering Index (CRI), Color Quality Scale (CQS) and Lumen Output (LO) of the 7000K in-cup packaging white LEDs (IPW-LEDs). The physical model of the 7000K IPW-LEDs is conducted by Light Tools software. By varying the concentration of the red phosphor from 0% to 0.36%, we use the Light Tools software to investigate the CRI, CQS, and LO of the 7000K IPW-LEDs. From the research results, it can be observed that the CRI and CQS can be increased to 85 and 71, respectively. However, the LO has a decrease in the increasing trend of the red phosphor concentration. This paper provides the new recommendation for the manufacturing of the IPW-LEDs.

Enhancement of efficiency and CCT uniformity for red phosphor thin films, red LEDs and laminated white LEDs based on near-ultraviolet LEDs using MgO nanoparticles.

Red phosphor thin films (PTFs) with different MgO nanoparticle concentrations for near-ultraviolet (NUV) LEDs were prepared based on their strong scattering effect; red LEDs and laminated white LEDs were packaged further. SEM and XRD showed that CaAlSiN3:Eu2+ (CASN) and MgO nanoparticles were uniformly distributed in silicone resin and their crystal structure remained unchanged. The phosphor conversion efficiency (PCE) had a maximum value of 83.15% when the MgO nanoparticle concentration was 15 wt%. An increase of concentration can improve the spatial distribution uniformity of photonics for 410 nm, 627 nm and 660 nm. Fluorescence lifetime showed that the value is positively correlated with concentration change. The packaged red LED luminous flux reaches a maximum of 20.337 lm at a concentration of 15 wt%. The laminated white LED showed that the MgO nanoparticle concentration can be used to adjust the correlated color temperature (CCT) from 4322 K to 1987 K. Under similar CCT, the red phosphor concentration is only 1.83 wt%, the dosage is reduced by 56.12%, and the corresponding luminous efficiency of radiation (LER) and luminous efficiency (LE) are 296.03 lm W−1 and 73.72 lm W−1 respectively. The increase was 11.42%, the decrease was 10.14%, the color rendering index (CRI) increased from 90.6 to 91.8, and CCT uniformity increased from 82.04% to 89.27% with an increase of 8.81%. Research shows that MgO nanoparticles have potential application value in the preparation of high-quality white LEDs.

Improving CQS, CRI and LO of the 5600K RP-WLEDs by Red-emitting Conversion Phosphor

In the few last decades, Light-emitting diodes (LEDs) is considered the newest solid-state lighting technique advancement in both industry and civil lighting. In this paper, we improve the Color rendering index (CRI), Color quality scale (CQS) and lumen output (LO) of the 5600 K remote-packaging white LEDs (RP-WLEDs) by the red-emitting conversion Sr2Si5N8:Eu2+ phosphor. The influence of the red phosphor concentration on the CQS, CRI, and LO are proposed and demonstrated by using Mie Theory with Mat Lab and Light Tools software. The results draw that CRI, CQS, and LO are significantly affected by the red phosphor concentration, which can provide a potential practical recommendation for manufacturing RP-WLEDs. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License .

Novel lighting properties of white LEDs with two-layered remote phosphor package using red-emitting α-SrO·3B2O3:Sm2+ phosphor

Abstract This paper investigates a method for improving the lighting performance of white light-emitting diodes (WLEDs), packaged using two separating remote phosphor layers, yellow-emitting YAG:Ce phosphor layer and red-emitting α-SrO·3B2O3:Sm2+ phosphor layer. The thicknesses of these two layers are 800 μm and 200 μm, respectively. Both of them have been examined at average correlated color temperatures (CCT) of 7700 K and 8500 K. For this two-layer model, the concentration of red phosphor has been varied from 2 % to 30 % in the upper layer, while in the lower layer the yellow phosphor concentration was kept at 15 %. It was found interesting that the lighting properties, such as color rendering index (CRI) and luminous flux, are enhanced significantly, while the color uniformity is maintained at a level relatively close to the level in one-layer configuration (measured at the same correlated color temperature). Besides, the transmitted and reflected light of each phosphor layer have been revised by combining Kubelka-Munk and Mie-Lorenz theories. Through the analysis, it is demonstrated that the packaging configuration of two-layered remote phosphor that contains red-emitting α-SrO·3B2O3:Sm2+ phosphor particles provides a practical solution to general WLEDs lighting.

A chromaticity-tunable white LED by screen-printing red phosphor coating on PiG plates

Currently, phosphor-in-glass (PiG) approach draws great attention because of its excellent thermal resistance and facile process in w-LED fabrication. However, the absence of red emissive component results in poor chromaticity quality, which greatly restricts its application in the high-quality indoor lighting. In the present work, a transparent garnet-based PiG was successfully prepared by introducing the Y3Al4.5Ga0.5O12:Ce3+(YAGG) green phosphor into TeO2-based glass matrix, and we demonstrated the possibility offered by the screen-printing technique for warm w-LED applications by coupling the PiG plate stacked with a red phosphor coating on commercial InGaN LED. The microstructures and luminescent properties of them were investigated in detail. After simply varying the red phosphor concentration as well as the YAGG PiG thickness, a facile chromaticity tuning for the thus-fabricated LED was achieved in the range changing from cool white to warm white. Moreover, this developed luminescent material presented an excellent heat-resistance performance. Hopefully, the red phosphor coated PiG color converter is applicable in the long-lifetime high-power color-tunable w-LEDs.

Synthesis, structure and photoluminescence properties of (Sr,Ca)AlSiN3:Eu2+ phosphor for white light emitting diodes with controllable optical performance

A series of SryCa1−x−yAlSiN3:xEu2+ (x = 0–0.01, y = 0–0.8) phosphors have been successfully prepared by solid state reaction under atmospheric pressure. All the phosphors exhibit orthorhombic crystal structure similar with CaAlSiN3 structure. It is found that the emission bands for all Ca1−xAlSiN3:xEu2+ phosphors are centered at ~650 nm and fluorescence quenching has been observed along with the increase of Eu2+ concentration in host materials. Through substitution of Ca2+ by Sr2+, an expected red emission peak (625 nm) and enhanced luminescent intensity can be achieved. The obtained Sr0.8Ca0.192AlSiN3:0.008Eu2+ phosphor was further used as efficient red component to fabricate white light emitting diodes (LEDs). Under the optimized condition of LED packaging, the white LEDs own the excellent optical properties with luminous efficiency of 90.6 lm/W and an ideal color rendering index (Ra = 82). Furthermore, the color correlated temperature of white LEDs can be simply adjusted through changing the red phosphor concentration and dispensing package saves time.

Hybrid 2D photonic crystal-assisted Lu3Al5O12:Ce ceramic-plate phosphor and free-standing red film phosphor for white LEDs with high color-rendering index.

This paper reports the combined optical effects of a two-dimensional (2D) SiNx photonic crystal layer (PCL)-assisted Lu3Al5O12:Ce (LuAG:Ce) green ceramic-plate phosphor (CPP) and a free-standing (Sr,Ca)AlSiN3:Eu red film phosphor to enhance luminous efficacy, color rendering index (CRI), and special CRI (R9) of LuAG:Ce CPP-capped white light-emitting diodes (LEDs) for high-power white LEDs at 350 mA. By introducing the 2D SiNx PCL, the luminous efficacy was improved by a factor of 1.25 and 1.15 compared to that of the conventional flat CPP-capped LED and the thickness-increased CPP-capped LED (with a thickness of 0.15 mm), respectively, while maintaining low color-rendering properties. The combining of the free-standing red film phosphor in the flat CPP-capped, the 2D PCL-assisted CPP-capped, and the thickness-increased CPP-capped LEDs led to enhancement of the CRI and the special CRI (R9); it also led to a decrease of the correlated color temperature (CCT) due to broad wavelength coverage via the addition of red emission. High CRI (94), natural white CCT (4450 K), and acceptable luminous efficacy (71.1 lm/W) were attained from the 2D PCL-assisted LuAG:Ce CPP/free-standing red film phosphor-based LED using a red phosphor concentration of 7.5 wt %. It is expected that the combination of the 2D PCL and the free-standing red film phosphor will be a good candidate for achieving a high-power white CPP-capped LED with excellent CRI.