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.
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 (Presented at SPIE OPTO: January 31, 2017; Published: 20 April 2017); https://doi.org/10.1117/12.2252513.5398643881001.
Conference Presentations are recordings of oral presentations given at SPIE conferences and published as part of the conference proceedings. They include the speaker's narration along with a video recording of the presentation slides and animations. Many conference presentations also include full-text papers. Search and browse our growing collection of more than 14,000 conference presentations, including many plenary and keynote presentations.
Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon