LED and Optical Device Packaging and Materials

Lin, Yuanchang; Zhou, Yan; Tran, Ngoc Nguyen; Shi, Frank G.

doi:10.1007/978-0-387-78219-5_18

Cited by 14 publications

(15 citation statements)

References 32 publications

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“…Among attempts to overcome these stability problems, the idea of encapsulating the phosphor in an inert binder has been extensively explored. [ 7 ] For this approach to work, the encapsulant needs to isolate the phosphor whilst maintaining the original transmittance, refractive index, thermal management properties, and structural integrity over the lifetime of the emitting device.…”

Section: Doi: 101002/adma201000493mentioning

confidence: 99%

Stable Efficient Solid‐State White‐Light‐Emitting Phosphor with a High Scotopic/Photopic Ratio Fabricated from Fused CdSe–Silica Nanocomposites

et al. 2010

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Section: Doi: 101002/adma201000493mentioning

confidence: 99%

Stable Efficient Solid‐State White‐Light‐Emitting Phosphor with a High Scotopic/Photopic Ratio Fabricated from Fused CdSe–Silica Nanocomposites

et al. 2010

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“…During the last decade, light‐emitting diodes (LEDs) have replaced incandescent, fluorescent, and neon lamps due to their ability to produce high luminosity at low currents and voltages . Besides, they have low‐power consumption, comparatively longer service lives, and can be formed into different shapes.…”

Section: Introductionmentioning

confidence: 99%

“…LEDs are used in a variety of lighting applications, including automotive lighting, indoor and outdoor lighting and backlighting for liquid‐crystal display laptops, mobile phones, and televisions. The LED package includes a LED chip mounted on a lead frame, gold wires for electrical connection, and an encapsulant . The encapsulant is an optical grade polymer that protects the device from dust and moisture.…”

Section: Introductionmentioning

confidence: 99%

“…These resins exhibit good thermal stability and mechanical properties and for that reason are widely used for electronic packaging application . Epoxy monomers employed for LEDs encapsulation are either aromatic diglycidyl ether of bisphenol‐A (DGEBA) or cycloaliphatic epoxides cationically cured using thermal cationic initiator or cured thermally by an anhydride . However, there are several disadvantages associated with the thermal cure of epoxy formulations such as high cure temperature (>120 °C), long period of curing schedules requiring stringent process control to avoid failure of the devices, and high consumption of energy .…”

Section: Introductionmentioning

confidence: 99%

“…During the last decade, light-emitting diodes (LEDs) have replaced incandescent, fluorescent, and neon lamps due to their ability to produce high luminosity at low currents and voltages. [1] Besides, they have low-power consumption, comparatively longer service lives, and can be formed into different shapes. LEDs are used in a variety of lighting applications, including automotive lighting, indoor and outdoor lighting and backlighting for liquid-crystal display laptops, mobile phones, and televisions.…”

Section: Introductionmentioning

confidence: 99%

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Encapsulants for light‐emitting diodes from visible light‐cured epoxy monomers

Schroeder

Erba

Arenas

et al. 2013

Polymers for Advanced Techs

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During the last decade, light‐emitting diodes (LEDs) have replaced incandescent, fluorescent, and neon lamps due to their ability to produce high luminosity at low currents and voltages. LEDs are currently encapsulated by thermally curable epoxy resins. However, long periods of curing at high temperature result in high consumption of energy and require stringent process control to avoid failure of the devices. In addition, the thermal cure results in yellowing of the encapsulant, which decreases the efficiency of the LED. In recent years, photoinitiated polymerization has received much interest as it congregates a wide range of economic and ecological benefits. Cationic photoinitiators, such as diaryliodonium salts, generate Brønsted acid in situ, which initiates polymerization. The process can be triggered on demand by irradiating the mixture with light. Results from the present research reveal that cycloaliphatic epoxy monomers, photoactivated with an iodonium salt and Camphorquinone, polymerize readily under visible light irradiation (470 nm) in the absence of external heating. The partial replacement of cycloaliphatic epoxy with aromatic diglycidyl ether of bisphenol‐A (DGEBA) is an effective means of improving the refractive index of the material and consequently the efficiency of the photoemission. Visible light polymerization of DGEBA pure proceeds at a slow rate; however, it is enhanced by the increase in temperature during the polymerization of the highly reactive cycloaliphatic monomer. From results obtained in the present research, it may be concluded that visible light polymerization of epoxy monomers is a promising route for the processing of LED encapsulants. Copyright © 2013 John Wiley & Sons, Ltd.

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Enhanced Luminescence Characteristics of Remote Yellow Silicate Phosphors Printed on Nanoscale Surface‐Roughened Glass Substrates for White Light‐Emitting Diodes

Kim

Eswaran

Kwon

et al. 2016

Advanced Optical Materials

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techniques, [ 6,13,16 ] and new phosphor structures [ 17,18 ] for better performance of white LED structures. However, there have been limited improvements in luminous effi cacy, which still remains a serious challenge hindering commercial success.Trapped loss of light in the air-gap (due to backward photons) and total internal refl ection (TIR) arising within the remote structure are the main factors that critically limit the light extraction. [19][20][21] The reported earlier methods such as scattered photon extraction [ 22 ] and diffused refl ection cup approach [ 23 ] have mainly improved the extraction of back refl ected light. By contrast, few studies to enhance the luminous effi cacy by reducing the TIR in the phosphor part have been reported. Our approach in this study is to adopt a simple nanoscale surface roughening technique to enhance the luminous efficacy by minimizing the TIR at the air-phosphor layer and airglass substrate interface of a remote phosphor LED consisting of yellow phosphor screen-printed on a glass substrate. In the past, surface roughening or surface texturing approaches have been applied to the top n-GaN layer of blue InGaN LED chips to enhance blue light emission by minimizing TIR at the semiconductor-air interface. [24][25][26] Notwithstanding the promising results of surface roughening methods, there have been very limited reports on the deployment of surface texturing techniques for the phosphor layer. One related report is about the random texturing in the case of yttrium aluminum garnet (YAG) phosphor by means of an imprint technique which resulted in an increased luminous fl ux by ≈5.4%. [ 27 ] A patterned YAG phosphor created by pulsed spray coating on a transparent silicone encapsulant resin using a circular mask was reported without increasing the luminous effi cacy. [ 28 ] In this work, we explore a simple surface roughening technique of the glass substrate used as a base for printable remote silicate phosphor, (Ba,Sr,Ca) 2 SiO 4 :Eu 2+ , for the purpose of enhancing the luminescence performance. Compared to other YAG-based phosphors, this yellow silicate phosphor is known to possess higher luminous effi cacy and to have advantages in commercial utilization and cost-effectiveness. We recently reported the utilization of a glass substrate for printable silicate Nonconventional ways to modify phosphor structures have been reported to enhance the overall luminous effi cacy of white light-emitting diodes (LED). Here, a nanoscale texturing technique of a glass substrate with the simple printing process of yellow (Ba,Sr,Ca) 2 SiO 4 :Eu +2 silicate phosphor paste is combined to achieve enhanced white luminescence performance. It is demonstrated that the luminous effi cacy of the resulting printed phosphor layer can be enhanced by ≈16% as a result of controlling surface roughness of the substrate up to 151 nm. The substantial improvement obtained by texturing both sides of the substrate is attributed to the reduction of total internal refl ection of rays at the glass-air interfac...

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LED and Optical Device Packaging and Materials

Cited by 14 publications

References 32 publications

Stable Efficient Solid‐State White‐Light‐Emitting Phosphor with a High Scotopic/Photopic Ratio Fabricated from Fused CdSe–Silica Nanocomposites

Stable Efficient Solid‐State White‐Light‐Emitting Phosphor with a High Scotopic/Photopic Ratio Fabricated from Fused CdSe–Silica Nanocomposites

Encapsulants for light‐emitting diodes from visible light‐cured epoxy monomers

Enhanced Luminescence Characteristics of Remote Yellow Silicate Phosphors Printed on Nanoscale Surface‐Roughened Glass Substrates for White Light‐Emitting Diodes

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