Angular CCT Uniformity of Phosphor Converted White LEDs: Effects of Phosphor Materials and Packaging Structures

Shuai, Yun; He, Yongzhi; Tran, Ngoc Nguyen; Shi, Frank G.

doi:10.1109/lpt.2010.2092759

Cited by 86 publications

(26 citation statements)

References 9 publications

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“…Figure 4 shows the angular-dependent CCTs of dispense, coating and hybrid phosphor structure. To evaluate the light quality for white LED, the difference of angular CCT deviation between the normal and large angle is an important standard to evaluate in the SSL application [26]. The larger CCT deviation would lead to the yellow ring phenomenon and generate the non-uniform white color at the different angle [27].…”

Section: Methodsmentioning

confidence: 99%

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Enhancement of luminous efficiency by hybrid structure for warm white light-emitting diodes

et al. 2014

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This study demonstrates the hybrid structure with high lumen efficiency and uniform angular-dependent correlated color temperature (CCT) for warm white LED. Compared to the conventional structures, the hybrid structure combines the advantage of the two different fabrication methods including dispense and pulse spray method together, which can produce the high quality lighting source. The experimental results indicate that the hybrid structure yielded higher lumen efficiency than conventional phosphor structure because of the gradual refractive index difference from the coating layer to the dispense layer. Moreover, the CCT deviations of the hybrid phosphor structure could be reduced to 65 K in range of −70 to 70 degrees. This is attributed to the uniform color mixing of the blue, yellow and red band in the hybrid phosphor structure. In addition, the chromaticity coordinate shift compared to the hybrid structure with the dispense structure are almost the same at a current regulation from 20 mA to 500 mA. We believe that the technology of the hybrid structure with high lumen efficiency and uniform angular-dependent CCT is suitable for in the general lighting application.

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Section: Methodsmentioning

confidence: 99%

“…The larger CCT deviation would lead to the yellow ring phenomenon and generate the non-uniform white color at the different angle [27]. The definition of the CCT deviation is calculated as follows [26]:…”

Section: Methodsmentioning

confidence: 99%

Enhancement of luminous efficiency by hybrid structure for warm white light-emitting diodes

et al. 2014

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“…[6][7][8][9][10] However, the architecture of a remote phosphor LED module differs considerably regarding the size, geometry, and construction of the light source configuration, which permits completely different trends and behavior. In this paper, a remote phosphor concept in which the phosphor surface is only a portion of the total emitting surface of the remote phosphor module is proposed (see Fig.…”

Section: Introductionmentioning

confidence: 99%

Spot phosphor concept applied to a remote phosphor light-emitting diode light engine

2016

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Abstract. Although remote phosphor technology outperforms conformal phosphor technology for midpower applications, one of the limiting factors due to its impact on the total cost is the amount of phosphor required. Furthermore, an important loss mechanism in remote phosphor light-emitting diode (LED) technology is the reabsorption of recycled, downconverted light by the phosphor. An obvious solution to this issue is to enable a light path for the converted light, such that further interactions with the phosphor element are avoided. We propose a spot phosphor concept to achieve this goal. To explore this configuration, a simulation model of a phosphor element is devised and validated. The optical input parameters are based on experimental data and the application of the inverse adding-doubling method. The resulting configuration, along with a long-pass filter, is shown to be a potential solution for reduction of phosphor usage. The moderate decrease in the light extraction ratio (LER) when applying the spot concept is partly attributed to the losses in the secondary optics needed to narrow the LED beam; the combination of the spot concept configuration with a directional light source such as a laser diode is shown to be a powerful combination for the enhancement of the LER. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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“…As a result, white light rays from one LED chip are close to white at the center, but increasingly yellowish toward the periphery; the result is the 'yellow-ring effect' [8,9]. This can be reduced with adjusted shape of color converting elements and LED package structure [10][11][12][13]. Diffuser layers were used to diffuse blue rays so that optical path lengths in all direction become similar.…”

Section: Introductionmentioning

confidence: 99%

Phosphor-in-glasses composites containing light diffusers for high color uniformity of white-light-emitting diodes

Chung

Heo

2015

J Sol State Light

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ZrO 2 light diffuser layers was placed on phosphor-in-glass composites (PiGs) to improve color uniformity of white-light-emitting diodes (white LEDs). Color coordinates of central part and periphery of white LEDs were (0.34, 0.38) and (0.36, 0.43), respectively; difference between two area decreases with the introduction of a diffuser layer. Color temperature difference also decreased from 770 to 464 K. The addition of diffuser layers reduced the luminous efficacy of the white LEDs from 90.3 to 83.4 lm/W.

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Angular CCT Uniformity of Phosphor Converted White LEDs: Effects of Phosphor Materials and Packaging Structures

Cited by 86 publications

References 9 publications

Enhancement of luminous efficiency by hybrid structure for warm white light-emitting diodes

Enhancement of luminous efficiency by hybrid structure for warm white light-emitting diodes

Spot phosphor concept applied to a remote phosphor light-emitting diode light engine

Phosphor-in-glasses composites containing light diffusers for high color uniformity of white-light-emitting diodes

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