An Investigation of the Optical Analysis in White Light-Emitting Diodes With Conformal and Remote Phosphor Structure

Chen, Kuo-Ju; Chen, Hsin-Chu; Lin, Chien-Chung; Wang, Chao-Hsun; Yeh, Chih-Ting; Tsai, Hsinhan; Chien, Shih-Hsuan; Shih, Min‐Hsiung; Kuo, Hao‐Chung

doi:10.1109/jdt.2013.2272644

Cited by 27 publications

(7 citation statements)

References 44 publications

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“…This saturation of lumen output can be an indication that signals too many blue photons are now confined in LED due to high reflectivity. To evaluate the uniformity of the LED CCT, the parameter called ΔCCT is defined as the difference between the CCT(max) and the CCT(min) [24]. As shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

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Improvement of light quality by DBR structure in white LED

Lin¹,

Chen²,

Wang³

et al. 2014

Opt. Express

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This study demonstrates the application of DBR structure into the remote phosphor structure to improve the angular correlated color temperature (CCT) deviation in white light-emitting diodes (WLEDs). In the experiment, the LED device with DBR structure yielded a higher luminous efficiency than a conventional structure. The CCT deviation can be improved from 1758K to 280K in a range of -70 to 70 degree and the luminous flux increases more than 10% due to the enhancement of the light extraction of the blue light. Moreover, the reflectance of the different DBR structures is analyzed with different angles to reveal the reasons of such improvements. As the result, this LED device with DBR structure shows the great potential to use as the next generation lighting source.

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Section: Resultsmentioning

confidence: 99%

“…5(b). This yellow ring phenomenon has been studied extensively, and its cause could be attributed to the inherent Lambertian pattern of blue rays [24,25]. With the DBR structure and the reduction of delta CCT, this phenomenon can be eliminated significantly, such as in Fig.…”

Section: Resultsmentioning

confidence: 99%

Improvement of light quality by DBR structure in white LED

Lin¹,

Chen²,

Wang³

et al. 2014

Opt. Express

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“…To find out the possible solutions, optical simulation is necessary. To assess the light field uniformity, OptisWorks software based on ray-tracing and Monte Carlo method is employed to simulate the light field of flexible white LED structures [25,26]. In the ray tracing simulation, the total lighting area is 43 mm x 43 mm and total LED chip number is 9 pcs.…”

Section: Optical Simulationmentioning

confidence: 99%

Large-area, uniform white light LED source on a flexible substrate

et al. 2015

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This study demonstrates the flexible white LED structure with high lumen efficiency and uniform optical performance for neutral white and warm white CCT. Flip-chip LEDs were attached on a polyimide substrate with copper strips as electrical and thermal conduction paths. Yellow phosphors are mixed with polydimenthysiloxane (PDMS) to provide mechanical support and flexibility. The light efficiency of this device can reach 120 lm/W and 85% of light output uniformity of the emission area can be achieved. Moreover, the optical simulation is employed to evaluate various designs of this flexible film in order to obtain uniform output. Both the pitch between the individual devices and the thickness of the phosphor film are calculated for optimization purpose. This flexible white LED with high lumen efficiency and good reliability is suitable for the large area fixture in the general lighting applications.

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“…One is to coat the LED die with a phosphor; the other is to divide a phosphor into sheets and separate the sheets away from the die. Both methods have their respective strengths [3,4]. Whichever packaging method is applied for LEDs, any process errors or design defects that occur during LED packaging can induce nonuniform spatial color distribution, also known as the "yellow ring" [5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Combining near-field hyperspectral imaging and far-field spectral-angular distribution to develop mid-field white LED optical models with spatial color deviation

Lee

Chen

2016

Opt. Express

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The integration of spatial distribution of light intensity and color in the midfield is instrumental for LED optical design. On the basis of this rationale, we proposed an accurate and convenient method for developing white LED optical models. Near-field hyperspectral images and far-field spectral-angular distributions were integrated to illustrate changes in spatial light intensity and color distribution in the mid-field, to the exclusion of the absorption, conversion, and scattering of phosphors. The corresponding optical models were developed for three LED samples under different packaging conditions. Their normalized cross-correlation values for spatial light intensity and correlated-color-temperature distribution between simulation and measurement averaged as high as 0.995 and 0.99 respectively, which validated the accuracy and feasibility of the proposed method.

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An Investigation of the Optical Analysis in White Light-Emitting Diodes With Conformal and Remote Phosphor Structure

Cited by 27 publications

References 44 publications

Improvement of light quality by DBR structure in white LED

Improvement of light quality by DBR structure in white LED

Large-area, uniform white light LED source on a flexible substrate

Combining near-field hyperspectral imaging and far-field spectral-angular distribution to develop mid-field white LED optical models with spatial color deviation

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