Chromaticity-tunable phosphor-in-glass for long-lifetime high-power warm w-LEDs

Chen, Hui; Lin, Hang; Xu, Jü; Wang, Bo; Lin, Zebin; Zhou, Ji‐Xun; Wang, Yuansheng

doi:10.1039/c5tc01057h

Cited by 140 publications

(73 citation statements)

References 41 publications

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“…The optical absorption bands E1 and E2 were shifted to higher energy and the exciton band was blue shifted from the bulk value. This interpretation is agreement with that from theoretical investigations and previous work conducted by Chen et al, [21], Brus [22], and Rossetti et al [23]. Similar behavior was reported by Lippens et al [24], whereby the valence and conduction bands move down and up depending on the relative values of the effective mass of an electron (  e m ) and hole (  h m ).…”

Section: Resultssupporting

confidence: 82%

“…On the other hand, the absorption spectra were fitted using the Lorentz model to quantitatively obtain the energy of the band-to-band transitions, as shown in Figure (5). According to this model, the two absorption bands E1 and E2 are attributed to the 1S-1P and 1S-1S transitions of ZnS nanoparticles, respectively [21]. Obviously, the electronic properties of the ZnS nanoparticles are strongly affected by size in the entire measured frequency range.…”

Section: Resultsmentioning

confidence: 99%

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Synthesis, Characterization, and Size Control of Zinc Sulfide Nanoparticles Capped by Poly(ethylene glycol)

Allehyani

Seoudi

Said

et al. 2015

Journal of Elec Materi

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Zinc sulfide nanoparticles were synthesized with controllable size via chemical precipitation. highresolution transmission electron microscopy (HRTEM) and X-ray powder diffraction (XRD) showed that the samples were grown with the cubic phase; the particle size was varied by varying the molar ratios of zinc chloride and sodium sulfide in the presence of poly(ethylene glycol). The optical band gap was calculated on the basis of ultraviolet-visible spectroscopy (UV-VIS) and ranged from 4.13 eV to 4.31 eV depending on the particle size. Surface passivation and adsorption of poly(ethylene glycol) on the nanoparticles was explained on the basis of Fourier transform infrared measurements (FTIR).

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Section: Resultssupporting

confidence: 82%

Section: Resultsmentioning

confidence: 99%

Synthesis, Characterization, and Size Control of Zinc Sulfide Nanoparticles Capped by Poly(ethylene glycol)

Allehyani

Seoudi

Said

et al. 2015

Journal of Elec Materi

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“…The increase of CCT can be attributed to the reduction of orange colors which shifts the overall color of wLED to blue. The simultaneous increase in CCT and CRI values has been also reported from other wLEDs . The color reproduction range was calculated based on the spectra, and it was clearly determined that the range had been widened, as shown in Figure .…”

Section: Introductionsupporting

confidence: 58%

Nd³⁺‐Doped Silicate Glasses as an Efficient Color Filter to Improve the Color Gamut of a White LED

Han

Kim

Chung³

et al. 2017

J Am Ceram Soc

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Nd 3+-doped silicate glass (Nd-glass) was employed as a color filter for a white LED based on red and green phosphor (RG-LED), to manipulate the photoluminescence spectral shape and thus to provide a wider color gamut. The hypersensitive transition of Nd 3+ : 4 I 9/2 ? 4 G 5/2 , 2 G 7/2 was adjusted via glass composition and Nd concentration, and improved absorbance as well as reduced the absorption bandwidth. The effective absorption of the Nd-glass at~580 nm reduced the spectral linewidth of the green and red emissions, improving the color reproduction range. The color gamut of the RG-LED was improved from 75.3% to 81.6% NTSC by the introduction of Nd-glass as a color filter. Reliability under high operating current and high temperature were also examined and discussed. K E Y W O R D Sglass, optical materials, photoluminescence, rare earths, silicates | INTRODUCTIONLiquid crystal displays (LCD) require a white back light unit (BLU) with a proper spectral combination of blue, green, and red emission for color reproduction. A white light emitting diode composed of red and green phosphors with a blue LED chip (RG-LED) has been widely used for the LCD-BLU light source.1-3 Since a wide color gamut can be achieved using primary colors 4 and the well-matched spectrum of the white LED (wLED) to the red, green, and blue (RGB) color filters of LCDs, 2 the broad spectral bandwidths of green and red emissions from the phosphors practically restricts the potential color reproduction range of the resultant LCD. In contrast, quantum dots (QDs) exhibit a narrow spectral bandwidth at the designated green and red emission peaks due to their characteristic exciton transitions, and thus have recently begun to be applied to highquality LCDs with wide color gamut. 5,6 However, QDs require hermetic passivation layers to protect them from degradation resulting from interaction with the atmosphere 6 and they have a higher production cost than conventional wLEDs. Thus, for cost-effective production of high-quality LCDs, it is highly desirable for conventional RG-LEDs to have the proper spectral shape. The visible emission spectra of RG-LEDs can be manipulated if the proper color filter can be introduced. Nd 3+ has strong absorption due to the 4 I 9/2 ? 4 G 5/2 , 2 G 7/2 transition, which is mostly centered at~580 nm, and can effectively modify the photoluminescence (PL) spectra of the RG-LED. Thus, a silicate glass doped with Nd 3+ can be a good color filter for spectral shape adjustment. As schematically drawn in Figure 1, a new configuration of RG-LED can be proposed using Nd 3+ -doped glass (Nd-glass), which absorbs the orange emission band and thus narrows the emission bandwidth of the green and red PL spectra from the currently employed phosphors. The Nd 3+ : 4 I 9/2 ? 4 G 5/2 , 2 G 7/2 transition is a characteristic hypersensitive transition, which is highly sensitive to changes in the local structure involving the Nd 3+-ion, such as the coordination number, bond strength, covalency, and symmetry of the crystalline field...

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“…The wLED fabricated using this concentration has a high LE of 92 lm W −1 , a CCT of 5414 K, and CRI of 68.4. 68 Chen et al 69 reported a modified YAG composition, YAG:Ce 3+ ,Mn 2+ ,Si 4+ with improved red component, incorporated into TeO 2 -B 2 O 3 -ZnO-Na 2 O-Al 2 O 3 based low-melting glass. This combination offers a homogeneous dispersion of phosphor in the matrix owing to the similar density and refractive index of the materials and thereby a reduced back scattering.…”

Section: Glass Phosphor Plate (Gpp)mentioning

confidence: 99%

“…Also, no considerable changes in other luminescence parameters like CCT, CRI and CIE were detected. 69 Zhang et al 70 developed a transparent YAG:Ce 3+ -based PiG. A thick film was coated on a glass substrate with the composition of TeO 2 -B 2 O 3 -ZnO-Na 2 O-Al 2 O 3 through a screen-printing process.…”

Section: Glass Phosphor Plate (Gpp)mentioning

confidence: 99%

Review—Phosphor Plates for High-Power LED Applications: Challenges and Opportunities toward Perfect Lighting

Kim

Viswanath

Unithrattil

et al. 2017

ECS J. Solid State Sci. Technol.

125

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In the past decades, solid-state lighting based on phosphors as energy converters has been a fast-growing industry. Phosphorconverted white light-emitting diodes (pc-wLEDs) enable high-power applications and miniaturization; for this, the phosphor must have good stability and high efficiency. In order to satisfy this demand, phosphor plates have been proposed instead of conventional organic-based phosphor binders. In this review, such phosphor plates are categorized according to their synthesis methods, and the advantages and disadvantages of each category are detailed. In addition, we describe the major aspects of phosphor plates that require improvement for applications in high-power devices. For the fabrication of high-power LEDs, the phosphor configuration, color purity, porosity, and particle size of glass powders are key properties to enhance the luminescence efficiency and reduce the generation of heat inside wLED packages, thereby improving thermal stability. The advent of authentic, energy-efficient lighting in the home and workplace significantly affected the modern way of life. Beginning with the mass production of incandescent light bulbs, and with the subsequent evolution of fluorescence lights, lighting technology has developed rapidly in the last few decades. Since Edison's incandescent bulb in 1879, 1 artificial lighting has been developed to increase power output and decrease the size of the system. The development of red light-emitting diodes (LEDs) in 1962 2 and blue LEDs in 1993 3 allowed innovation in lighting and display. In particular, combinations of blue LEDs and yellow phosphors are used for many applications because they can realize cheap and efficient white solid-state lighting with several advantages including long lifetimes, eco-friendly behavior, and the capacity of miniaturization. 4-6In phosphor-converted white LEDs (pc-wLEDs), the phosphor converter dispersed in silicon resin (phosphor-in-silicon; PiS) is directly packed on a blue InGaN chip.7 When driven by a bias current, the emitted blue light absorbed by the phosphor is emitted as yellow light; together with the transmitted blue light, this constitutes white luminescence. However, this method lacks a red component, which entails the drawbacks of a poor color rendering index (CRI) and limited correlated color temperature (CCT). To overcome these drawbacks, one proposed method mixes yellow phosphors with phosphors having green to red emissions under blue excitation. 8 In pc-wLEDs, the color is primarily determined by the ratio of the blue emission from the LED chip to the yellow to red emission from the phosphor. However, the efficacy and brightness are determined by the converted yellow to red emission, as it contributes the bulk of lumens. In this configuration, the heat generated from the LED chip and phosphor cannot be efficiently dissipated because of the poor thermal stability and weak thermal conductivity of the resin, which causes luminous decay and color shifting in white light-emitting diodes (wLEDs).9 When the tempe...

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Chromaticity-tunable phosphor-in-glass for long-lifetime high-power warm w-LEDs

Cited by 140 publications

References 41 publications

Synthesis, Characterization, and Size Control of Zinc Sulfide Nanoparticles Capped by Poly(ethylene glycol)

Synthesis, Characterization, and Size Control of Zinc Sulfide Nanoparticles Capped by Poly(ethylene glycol)

Nd³⁺‐Doped Silicate Glasses as an Efficient Color Filter to Improve the Color Gamut of a White LED

Review—Phosphor Plates for High-Power LED Applications: Challenges and Opportunities toward Perfect Lighting

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Chromaticity-tunable phosphor-in-glass for long-lifetime high-power warm w-LEDs

Cited by 140 publications

References 41 publications

Synthesis, Characterization, and Size Control of Zinc Sulfide Nanoparticles Capped by Poly(ethylene glycol)

Synthesis, Characterization, and Size Control of Zinc Sulfide Nanoparticles Capped by Poly(ethylene glycol)

Nd3+‐Doped Silicate Glasses as an Efficient Color Filter to Improve the Color Gamut of a White LED

Review—Phosphor Plates for High-Power LED Applications: Challenges and Opportunities toward Perfect Lighting

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Nd³⁺‐Doped Silicate Glasses as an Efficient Color Filter to Improve the Color Gamut of a White LED