Highly scattering layer for efficient LED light extraction (Conference Presentation)

Kyoungsik Kim; Changuk Kim; Seunghwa Baek

doi:10.1117/12.2252513

20 April 2017 Highly scattering layer for efficient LED light extraction (Conference Presentation)

Kyoungsik Kim, Changuk Kim, Seunghwa Baek

Proceedings Volume 10124, Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XXI; 101240J (2017) https://doi.org/10.1117/12.2252513
Event: SPIE OPTO, 2017, San Francisco, California, United States

Abstract

Light emitting diodes (LEDs) are used to very diverse fields because of their high efficiency and long life time. Especially, GaN-based LEDs has good properties such as high power and electrical stability, so it can be used for light source in many devices. However, because of large difference of refractive index between SiC substrate of LEDs and air, Fresnel reflection loss and Total internal reflection loss are occurred. For that reason, light extraction efficiency of LEDs is very low. In this study, we fabricate Alumina based scattering film and show light extraction efficiency of LEDs can be enhanced through attaching scattering film on SiC substrate. Alumina nanowires were fabricated by wet etching process of porous alumina layer. Nanowires were collapsed randomly by capillary force of water during drying process forming microscale ridges. This scattering film has extremely high transmittance and scattering value which is determined by etching time. The effective refractive index of the film lies between the refractive index of SiC and air. So attached scattering film on SiC substrate of LEDs creates gradually varying index distribution reducing Fresnel reflection loss. Microscale ridges of scattering film play as light scatterers, and incidence light scattered in all direction reducing incident angle dependence so they can reduce total internal reflection loss. Light extraction efficiency of scattering film attached LED is about 20% higher than bare LED.

Conference Presentation

Citation Download Citation

Kyoungsik Kim, Changuk Kim, and Seunghwa Baek "Highly scattering layer for efficient LED light extraction (Conference Presentation)", Proc. SPIE 10124, Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XXI, 101240J (20 April 2017); https://doi.org/10.1117/12.2252513

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KEYWORDS

Light emitting diodes

Light scattering

Scattering

Reflection

Silicon carbide

Refractive index

Nanowires

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