Improvement of Light Extraction Efficiency of LED Packages Using an Enhanced Encapsulant Design

Choi, Hyun-Su; Park, Joon Sik; Moon, Cheol-Hee

doi:10.3807/josk.2014.18.4.370

Cited by 7 publications

(2 citation statements)

References 20 publications

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“…5,6 Moreover, double-layer encapsulants with spherical concave and convex interfaces enhance the light output power by increasing the critical angle with the addition of a curved interface between the two encapsulant layers with different refractive indices. 7,8 In this work, we study the formation of caustic surfaces produced by refraction through conic optical interfaces considered as the LED chip encapsulant. We assume a point source as the LED chip, placed along the optical axis at arbitrary distances from the vertex of the surface.…”

Section: Introductionmentioning

confidence: 99%

Caustic produced by refractive conic surfaces

López-Bautista

Avendaño‐Alejo

Ponce-Hernández

et al. 2022

Current Developments in Lens Design and Optical Engineering XXIII

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We study the formation of caustic produced by refraction through conic surfaces, considering a point source placed along the optical axis at arbitrary distances from the vertex of refracting surface. We demand that the optical surface is represented by a mathematical function, which is smooth, continuous, and derivable. We implement an exact ray trace to obtain a monoparametric equation that describes a family of refracted rays, which are propagated as a function of the angle of emission from the point source for each ray. Subsequently, by using the envelope's method, we provide an analytical equation for the caustic surface as a function of all the parameters involved in the process of refraction. We analyze the paraxial approximation assuming a very small angle about the axis of the system. Additionally, we provide a formula, which describes the conditions for total internal reflection. Finally, we present the formation of caustic surfaces by considering a liquid polymer in a rotating vessel forming a paraboloid surface, also we present the caustic surface produced by the package of a Light Emitting Diode, to produce an uniform illumination pattern.

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Section: Introductionmentioning

confidence: 99%

Caustic produced by refractive conic surfaces

López-Bautista

Avendaño‐Alejo

Ponce-Hernández

et al. 2022

Current Developments in Lens Design and Optical Engineering XXIII

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“…Many people find that flat devices show similar LEEs compared to the structured devices [2,10,23,24]. However, the TIR and Fresnel losses still remain on the light extraction surface [11,16,[25][26][27], which should be alleviated to enhance the LEE of white LEDs.…”

Section: Introductionmentioning

confidence: 99%

Effect of Amorphous Photonic Structure Surface Mounted on Luminous Performances of White LED

Huang¹,

Chen

Nie

et al. 2022

Crystals

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We fabricated amorphous photonic structures (APSs) with different periods and hole diameters. The GaN-based white light emitting diodes (LEDs) at nominal correlated color temperatures (CCTs) of 5000 and 6000 K were surface mounted by these APSs. The electroluminescence (EL) measurements showed less luminous efficiency (LE) and higher CCT than the ones of the virginal white LEDs. However, the LEs of many APS-mounted white LEDs increased compared to white the LEDs without APSs at the same CCTs. A finite-difference time-domain (FDTD) simulation was carried out on the ASPs surface-mounted white LEDs and bidirectional scattering distribution functions (BSDFs) of different emissions were transferred to a Monte Carlo ray tracing simulation. The simulated LEs and CCTs conformed well to the experimental ones. The effects of the blue emission transmission and phosphor concentration were simulated to predict the absolute LE enhancement methods for white LEDs. At last, the hopeful APSs for high Les’ general lighting were discussed.

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Using nanoimprint lithography to improve the light extraction efficiency and color rendering of dichromatic white light-emitting diodes

Lee

Chen

et al. 2015

Nanoscale

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Despite the efficiency of gallium nitride (GaN)-based blue light-emitting diodes (LEDs), the light extraction arising from the packaging of the phosphor remains an important issue when enhancing the performance of dichromatic white LEDs. In this study, we employed a simple, inexpensive nanoimprinting process to increase both the light extraction efficiency and color rendering of dichromatic white LEDs. We employed the rigorous coupled wave approach (RCWA) to optimize the light extraction efficiency of yellow and blue light. We found that the presence of the light extracting structures could also improve the color rendering of the dichromatic white LEDs, due to the different light extraction efficiencies of the textured structures at different wavelengths. After fabricating inverted pyramid structures on the surface of the encapsulation layer, the intensity of the blue light at 455 nm increased by 20%. When we further considered the color rendering and correlated color temperature (CCT), the enhancement of blue light was 15% and that of yellow light was 4%. Meanwhile, the light extraction of the intensity dip near 490 nm was enhanced significantly (by 25%), resulting in an increased dip-intensity of light at 490 nm relative to the intensities of the blue and yellow light. Accordingly, the color rendering index (CRI) of this dichromatic white LED increased from 69 to 73. Because it improved both the light extraction efficiency and color rendering of dichromatic white LEDs, this simple method should be very helpful for enhancing their applications in solid state illumination.

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Improvement of Light Extraction Efficiency of LED Packages Using an Enhanced Encapsulant Design

Cited by 7 publications

References 20 publications

Caustic produced by refractive conic surfaces

Caustic produced by refractive conic surfaces

Effect of Amorphous Photonic Structure Surface Mounted on Luminous Performances of White LED

Using nanoimprint lithography to improve the light extraction efficiency and color rendering of dichromatic white light-emitting diodes

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