Effects of the refractive index of the encapsulant on the light-extraction efficiency of light-emitting diodes

Ming Ma; Frank W. Mont; Jaehee Cho; E. Fred Schubert; Gi Bum Kim; Cheolsoo Sone

doi:10.1364/OE.19.0A1135

Effects of the refractive index of the encapsulant on the light-extraction efficiency of light-emitting diodes

Ming Ma
, Frank W. Mont
, Jaehee Cho
, E. Fred Schubert
, Gi Bum Kim
, Cheolsoo Sone

Department of Semiconductor Science and Technology

Rensselaer Polytechnic Institute
Samsung

Research output: Contribution to journal › Journal article › peer-review

96 Scopus citations

Abstract

We investigate the effects of the refractive index of the encapsulant on the light-extraction efficiency (LEE) of light-emitting diodes (LEDs) for GaN LEDs (n ≈ 2.5) and AlGaInP LEDs (n ≈ 3.0). For nonabsorbing rectangular parallelepiped LED chips, as the refractive index of the encapsulant increases, the LEE first increases quasi-linearly, then increases sub-linearly, and finally a saturation is reached. Furthermore, LEDs with a dual-layer graded-refractive-index (GRIN) encapsulant (n_encapsulant1 = 1.57 and n_encapsulant2 = 1.41) is fabricated through a two-step curing process. We demonstrate that such an LED further enhances the LEE by reducing Fresnel reflection loss at the encapsulant/air interface by 35% compared with an LED encapsulated with a single-layer encapsulant (n_encapsulant = 1.57).

Original language	English
Pages (from-to)	A1135-A1140
Journal	Optics Express
Volume	19
Issue number	105
DOIs	https://doi.org/10.1364/OE.19.0A1135
State	Published - 2011.09.12

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@article{38569dd752bc486ab8aa339a0b9ff46f,

title = "Effects of the refractive index of the encapsulant on the light-extraction efficiency of light-emitting diodes",

abstract = "We investigate the effects of the refractive index of the encapsulant on the light-extraction efficiency (LEE) of light-emitting diodes (LEDs) for GaN LEDs (n ≈ 2.5) and AlGaInP LEDs (n ≈ 3.0). For nonabsorbing rectangular parallelepiped LED chips, as the refractive index of the encapsulant increases, the LEE first increases quasi-linearly, then increases sub-linearly, and finally a saturation is reached. Furthermore, LEDs with a dual-layer graded-refractive-index (GRIN) encapsulant (nencapsulant1 = 1.57 and nencapsulant2 = 1.41) is fabricated through a two-step curing process. We demonstrate that such an LED further enhances the LEE by reducing Fresnel reflection loss at the encapsulant/air interface by 35\% compared with an LED encapsulated with a single-layer encapsulant (nencapsulant = 1.57).",

author = "Ming Ma and Mont, \{Frank W.\} and Jaehee Cho and Schubert, \{E. Fred\} and Kim, \{Gi Bum\} and Cheolsoo Sone",

year = "2011",

month = sep,

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doi = "10.1364/OE.19.0A1135",

language = "English",

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journal = "Optics Express",

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TY - JOUR

T1 - Effects of the refractive index of the encapsulant on the light-extraction efficiency of light-emitting diodes

AU - Ma, Ming

AU - Mont, Frank W.

AU - Cho, Jaehee

AU - Schubert, E. Fred

AU - Kim, Gi Bum

AU - Sone, Cheolsoo

PY - 2011/9/12

Y1 - 2011/9/12

N2 - We investigate the effects of the refractive index of the encapsulant on the light-extraction efficiency (LEE) of light-emitting diodes (LEDs) for GaN LEDs (n ≈ 2.5) and AlGaInP LEDs (n ≈ 3.0). For nonabsorbing rectangular parallelepiped LED chips, as the refractive index of the encapsulant increases, the LEE first increases quasi-linearly, then increases sub-linearly, and finally a saturation is reached. Furthermore, LEDs with a dual-layer graded-refractive-index (GRIN) encapsulant (nencapsulant1 = 1.57 and nencapsulant2 = 1.41) is fabricated through a two-step curing process. We demonstrate that such an LED further enhances the LEE by reducing Fresnel reflection loss at the encapsulant/air interface by 35% compared with an LED encapsulated with a single-layer encapsulant (nencapsulant = 1.57).

AB - We investigate the effects of the refractive index of the encapsulant on the light-extraction efficiency (LEE) of light-emitting diodes (LEDs) for GaN LEDs (n ≈ 2.5) and AlGaInP LEDs (n ≈ 3.0). For nonabsorbing rectangular parallelepiped LED chips, as the refractive index of the encapsulant increases, the LEE first increases quasi-linearly, then increases sub-linearly, and finally a saturation is reached. Furthermore, LEDs with a dual-layer graded-refractive-index (GRIN) encapsulant (nencapsulant1 = 1.57 and nencapsulant2 = 1.41) is fabricated through a two-step curing process. We demonstrate that such an LED further enhances the LEE by reducing Fresnel reflection loss at the encapsulant/air interface by 35% compared with an LED encapsulated with a single-layer encapsulant (nencapsulant = 1.57).

UR - https://www.scopus.com/pages/publications/80052701583

U2 - 10.1364/OE.19.0A1135

DO - 10.1364/OE.19.0A1135

M3 - Journal article

AN - SCOPUS:80052701583

SN - 1094-4087

VL - 19

SP - A1135-A1140

JO - Optics Express

JF - Optics Express

IS - 105

ER -

Effects of the refractive index of the encapsulant on the light-extraction efficiency of light-emitting diodes

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