Improved color uniformity in white light-emitting diodes using newly developed phosphors

Daicho, Hisayoshi; Enomoto, Kiminori; Sawa, Hiroshi; Matsuishi, Satoru; Hosono, Hideo

doi:10.1364/oe.26.024784

Cited by 22 publications

(14 citation statements)

References 22 publications

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“…Phosphor‐converted white‐light‐emitting diodes (pc‐WLEDs) are emerging as an indispensable solid‐state light source due to their unique properties including but not limited to energy savings, environment‐friendliness, small volume, and long persistence . Until now, major challenges in pc‐WLEDs have been to achieve a high luminous efficacy, high chromatic stability, brilliant color‐rending index (CRI), and price competitiveness against fluorescent lamps, which rely critically on the phosphor properties . While the field of luminescent materials for solid‐state lighting has seen a tremendous increase in the past two decades, the most common way to generate white light is the combination of blue LED chips with yellow‐emitting phosphor materials .…”

Section: Introductionmentioning

confidence: 99%

“…2,5,6 Until now, major challenges in pc-WLEDs have been to achieve a high luminous efficacy, high chromatic stability, brilliant color-rending index (CRI), and price competitiveness against fluorescent lamps, which rely critically on the phosphor properties. [7][8][9][10] While the field of luminescent materials for solid-state lighting has seen a tremendous increase in the past two decades, the most common way to generate white light is the combination of blue LED chips with yellow-emitting phosphor materials. 11 However, the difference between individual degradation rates of chips and phosphors coated on chips would cause a chromatic aberration and a poor white light performance.…”

Section: Introductionmentioning

confidence: 99%

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Enhanced luminescence of manganese in singly doped white light zinc phosphate glass

et al. 2019

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On the basis of a kind of zinc phosphate oxynitride glass matrix with a broadband blue light, a series of manganese single‐doped glasses were obtained. A broader red emission with the higher intensity belonging to the Mn2+ ion was observed in this glass matrix. The mechanism of the emission from Mn2+ ions was clarified through Mn3+ as an “energy acquisition probe” to replace complex dynamic luminescence discussion, which was a fit explanation for the differences in luminescence behavior of Mn ions in prepared glasses at different degrees of redox. The research results indicated that the prepared manganese‐doped glass was a potential candidate as phosphor‐converted white‐light‐emitting diodes. An encapsulated white‐light‐emitting diode device based on this glass with 276 nm ultraviolet chip was achieved. It showed the CIE values of (0.33, 0.35), high CRI (Ra = 86), and low color temperature (5228 K).

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Enhanced luminescence of manganese in singly doped white light zinc phosphate glass

et al. 2019

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“…fdif(r) and fphos(r) are the function data of the diffuser and the dimension dispensation of phosphor particle. KN is the diffuser unit number for a single diffuser concentration and can be determined as below [25], [26]: (6) Where M(r) is the diffusive unit's mass distribution, proposed by the equation [27]: (7) ρdiff(r) and ρphos(r) are the density of diffuser and phosphor crystal. According to Mie theory, Csca could be acquired by the calculation below [28]: (8) Where k=2π/λ, and an and bn are computed as follows:…”

Section: Scattering Computationmentioning

confidence: 99%

Employing SiO2 nano-particles in conformal and in-cup structures of 8500 K white LEDs

Thi

That

2021

Bulletin EEI

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SiO2 nano-particles have been examined in a distant phosphor structure for the elevated luminous quality and better consistency of white light-emitting diodes with angular-dependent associated color temperature (CCT). The luminous scattering ability could be increased by applying SiO2 nano-particles contain silicone to the outside of the phosphorus coating. In specific, the strength of blue light at wide angles is increased and differences in CCT can be minimized. In addition, owing to the sufficient refractive indices of silicone-containing SiO2 nanoparticles between the air and phosphorus layers, the luminous flux was improved. This new configuration decreases angular-dependent CCT deviations in the range of -700 to 700 from 1000 to 420 K. In comparison, at a 120 mA driving current, the rise of lumen flux increased by 2.25% relative to an usual distant phosphor structure without SiO2 nano-particles. As a result, in a distant phosphor structure, the SiO2 nano-particles could not only enhance the uniformity of illumination but also enhance the output of light.

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“…This article uses 90 types of light sources including 3 CIE standard illumination light sources (A, D50, D65), 41 fluorescent light sources [6], 46 LED light sources in the market [38]- [42], and their color temperature ranges from 1717k to 6781K [43], [44]. They are numbered as light source 1, light source 2, light source 3• • • light source 90 respectively.…”

Section: A Light Sourcementioning

confidence: 99%

Study of Color Rendering Evaluation Method of Light Sources for Printing Matter

Lian

Liu

et al. 2020

IEEE Access

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Based on the optimization of color samples, we have developed a method to evaluate light sources' color rendering of printing matter. By performing Affinity Propagation (AP) Clustering Algorithm on the color appearance and spectra of the color printing atlas samples printed by a press, two typical color sample sets are obtained. The optimized color sample (OCS) set consists of these two typical color sample sets and it is presented by CMYK dot area coverage. The color rendering indexes (CRIs) CIE-R a , CRI2012, CIE-R f of 90 light sources are calculated by taking the OCS set, color printing atlas and standard color sample (SCS) set of CRI as the test color sample (TCS) set. By comparing the Absolute Difference (AD), Mean Absolute Difference (MAD), Coefficient of Variation (CV) and Spearman Correlation Coefficient (SCC) of the CRIs, we find that the indexes calculated by OCS set are closer to these indexes calculated by color printing atlas than by SCS set. Therefore, the OCS set is more suitable for printing applications. After output from a press and measured spectra, the OCS set with CMYK dot area coverage can be used as the TCS set to evaluate the color rendering of light sources for all printing matter output from this press. For proving the reliability of the results, that is, the universality of the OCS set to the presses, the OCS set with fixed CMYK dot area coverage is output from an another press and CRIs are calculated. The results show that OCS set we developed is better than the SCS set. This method can be used for color rendering evaluation of light sources for printing matter.

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Improved color uniformity in white light-emitting diodes using newly developed phosphors

Cited by 22 publications

References 22 publications

Enhanced luminescence of manganese in singly doped white light zinc phosphate glass

Enhanced luminescence of manganese in singly doped white light zinc phosphate glass

Employing SiO2 nano-particles in conformal and in-cup structures of 8500 K white LEDs

Study of Color Rendering Evaluation Method of Light Sources for Printing Matter

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