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Energy Express

Energy Express

  • Editor: Bernard Kippelen
  • Vol. 19, Iss. S5 — Sep. 12, 2011
  • pp: A1135–A1140

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

Ming Ma, Frank W. Mont, Xing Yan, Jaehee Cho, E. Fred Schubert, Gi Bum Kim, and Cheolsoo Sone  »View Author Affiliations


Optics Express, Vol. 19, Issue S5, pp. A1135-A1140 (2011)
http://dx.doi.org/10.1364/OE.19.0A1135


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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 non-absorbing 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).

© 2011 OSA

OCIS Codes
(230.3670) Optical devices : Light-emitting diodes
(310.4165) Thin films : Multilayer design

ToC Category:
Light-Emitting Diodes

History
Original Manuscript: June 3, 2011
Revised Manuscript: July 18, 2011
Manuscript Accepted: July 19, 2011
Published: August 16, 2011

Citation
Ming Ma, Frank W. Mont, Xing Yan, Jaehee Cho, E. Fred Schubert, Gi Bum Kim, and Cheolsoo Sone, "Effects of the refractive index of the encapsulant on the light-extraction efficiency of light-emitting diodes," Opt. Express 19, A1135-A1140 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-S5-A1135


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References

  1. E. F. Schubert, Light-Emitting Diodes, 2nd ed. (Cambridge University Press, 2006).
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