Improving the Angular Color Uniformity of Hybrid Phosphor Structures in White Light-Emitting Diodes

Chen, Kuo-Ju; Han, Hau-Vei; Lin, Bor‐Shyh; Chen, Hsin-Chu; Shih, Min‐Hsiung; Chien, Shih-Hsuan; Wang, Kuan Yu; Tsai, Hsinhan; Yu, Peichen; Lee, Po-Tsung; Lin, Chien-Chung; Kuo, Hao‐Chung

doi:10.1109/led.2013.2278336

Cited by 27 publications

(12 citation statements)

References 16 publications

(15 reference statements)

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“…The BTDF measurement could figure out the diffraction distribution with different incident angle [20,21], in this work, the BTDF measurement have been used to imitate the LED light source incident to the MC-PDMS film. Generally, the intensity of GaN based LED in different angles shows as a lambertian light distribution [22], and it would follow the below equation [8].…”

Section: Resultsmentioning

confidence: 99%

Improvement of emission uniformity by using micro-cone patterned PDMS film

et al. 2014

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Micro-patterned PDMS film was fabricated and combined with LED chip on board (COB) package to improve the emission uniformity of LED chip. The micro scale patterned sapphire substrate (PSS) was used as a mold to fabricate micro-cone patterned PDMS (MC-PDMS) film. A strong scattering effect from this MC-PDMS film can be verified by the high haze ratio and the Bi-directional Transmission effect. The angle dependent color temperature measurement system was used to measure the ΔCCT of COB with and without MC-PDMS. The measurement results indicate that the ΔCCT was reduced from 1025K to 428K. This improvement can effectively eliminate the yellow ring effect of LED chip. This technology can be thus considered as a cost-effective way for the next generation of light source packages.

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Section: Resultsmentioning

confidence: 99%

Improvement of emission uniformity by using micro-cone patterned PDMS film

et al. 2014

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“…As the driving current increased, the lumen output differences between the hybrid, dispense and the coating structures become larger. Moreover, the advantage of the hybrid structure could provide the gradual refractive index difference from the coating layer to the dispense layer and reduce the reflection loss in the interface [22]. Therefore, the hybrid structure has the higher luminous efficiency than the dispense and coating structures.…”

Section: Methodsmentioning

confidence: 99%

“…However, for the conformal-type phosphor structure, there are 60% backscattering lights reflected to the package [21] and these back-scattering photons are susceptible to reabsorption by the blue chip and thus reducing the luminous efficiency. To solve these problems, the hybrid structure [22] and the dual-layer phosphor structure [23] are employed to enhance the lumen output due to the reduced back light inside the package. From these past experiences, therefore, it is essential to reduce the backscattering light issue when the concentration of the phosphor increased, especially in the warm white LED.…”

Section: Introductionmentioning

confidence: 99%

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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“…3a). This finding implies that a large number of photons, emitted from the MQWs, are reflected by the large textures and return to the LED III, thereby leading to the chance of reabsorption [13]. The effects of height of texture on the ray tracing will be discussed for the LED I, LED II, and LED III at a later stage.…”

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confidence: 95%