• Title, Summary, Keyword: Light-extraction efficiency

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Direct printing process based on nanoimprint lithography to enhance the light extraction efficiency of AlGaInP based red LEDs

  • Cho, Joong-Yeon;Kim, Jin-Seung;Kim, Gyu-Tae;Lee, Heon
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • pp.171-171
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    • 2012
  • In this study, we fabricated the high-brightness AlGaInP-based red light emitting diodes (LED)s using by direct printing technique and inductive coupled plasma (ICP) reactive ion etching (RIE). In general, surface roughening was fabricated by wet etching process to improve the light extraction efficiency of AlGaInP-based red LED. However, a structure of the surface roughening, which was fabricated by wet etching, was tiled cone-shape after wet etching process due to crystal structure of AlGaInP materials, which was used as top-layer of red LED. This tilted cone-shape of surface roughening can improve the light extraction of LED, but it caused a loss of the light extraction efficiency of LED. So, in this study, we fabricated perfectly cone shaped pattern using direct printing and dry etching process to maximize the light extraction efficiency of LED. Both submicron pattern and micron pattern was formed on the surface of red LED to compare the enhancement effect of light extraction efficiency of LEDs according to the diameter of sapphire patterns.After patterning process using direct printing and ICP-RIE proceeded on the red LED, light output was enhanced up to 10 % than that of red LED with wet etched structure. This enhancement of light extraction of red LED was maintained after packaging process. And as a result of analyze of current-voltage characteristic, there is no electrical degradation of LED.

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A Study on Improvement of the Light Emitting Efficiency on Flip Chip LED with Patterned Sapphire Substrate by the Optical Simulation (광학 시뮬레이션을 이용한 Patterned Sapphire Substrate에 따른 Flip Chip LED의 광 추출 효율 변화에 대한 연구)

  • Park, Hyun Jung;Lee, Dong Kyu;Kwak, Joon Seop
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.28 no.10
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    • pp.676-681
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    • 2015
  • Recently many studies being carried out to increase the light efficiency of LED. The external quantum efficiency of LED, generally the light efficiency, is determined by the internal quantum efficiency and the light extraction efficiency. The internal quantum efficiency of LED was already reached to more than 90%, but the light extraction efficiency is still insufficient compared with the internal quantum efficiency because the total internal reflection is generated in the interface between the LED chip and air. Thus, we studied about flip chip LED with PSS and performed the optical simulation which find more optimized PSS for flip chip LED to increase the light extraction efficiency. Decreasing of the total internal reflection and effect of diffused reflection according to PSS improved the light extraction efficiency. To get more higher the efficiency, we simulated flip chip with PSS that the parameters are arrangement, edge spacing, radius, height and shape of PSS.

Improvement of Light Extraction Efficiency by Side Surface Texturing in Nitride-based Light-Emitting Diodes (질화계 발광다이오드의 측면 형상화를 이용한 광 추출 효율 향상)

  • Jang, Dong-Hyeon;Sim, Jong-In
    • Proceedings of the Optical Society of Korea Conference
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    • pp.95-96
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    • 2008
  • We theoretically investigated the influence of side surface texturing on the light extraction efficiency in nitride-based light-emitting diodes (LEDs). The light extraction efficiency was expected as 1.2 times larger in a LED with textured surfaces compared to without ones.

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Enhanced Internal Quantum Efficiency and Light Extraction Efficiency of Light-emitting Diodes with Air-gap Photonic Crystal Structure Formed by Tungsten Nano-mask

  • Cho, Chu-Young;Hong, Sang-Hyun;Kim, Ki Seok;Jung, Gun-Young;Park, Seong-Ju
    • Bulletin of the Korean Chemical Society
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    • v.35 no.3
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    • pp.705-708
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    • 2014
  • We demonstrate the blue InGaN/GaN multiple quantum wells light-emitting diodes (LEDs) with an embedded air-gap photonic crystal (PC) which was fabricated by the lateral epitaxial overgrowth of GaN layer on the tungsten (W) nano-masks. The periodic air-gap PC was formed by the chemical reaction of hydrogen with GaN on the W nano-mask. The optical output power of LEDs with an air-gap PC was increased by 26% compared to LEDs without an air-gap PC. The enhanced optical output power was attributed to the improvement in internal quantum efficiency and light extraction efficiency by the air-gap PC embedded in GaN layer.

Improvement of light extraction efficiency of display devices by using sub-wavelength scale structure

  • Kwon, Oh-Yung;Whang, Ki-Woong
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.1412-1414
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    • 2009
  • It is suggested that the light extraction efficiency of the display device can be improved by adoption of periodic array of sub-wavelength scale structures. The relief of the total reflection has been investigated using the rigorous coupled wave analysis (RCWA). Various shape of the sub-wavelength scale structure allowed to have non vanishing transmittance for the light rays with the incident angle bigger than the critical angle.

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Light-extraction enhancement of white LEDs with different phases of TiO2:0.01Eu3+ spheres

  • Mun, Ju Young;Raju, Ganji Seeta Rama;Park, Jin Young;Yang, Hyun Kyoung
    • Current Applied Physics
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    • v.17 no.4
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    • pp.527-532
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    • 2017
  • We report the synthesis of $TiO_2:0.01Eu^{3+}$ spheres by a solvothermal reaction method and their utilization in the enhancement of light-extraction efficiency. The light-extraction efficiency was enhanced by increasing the extraction probability of the internal and external reflected photons in the $YAG:Ce^{3+}$ yellow phosphor based white light-emitting diodes (WLEDs). The crystalline structure of $TiO_2:0.01Eu^{3+}$ spheres was investigated by an X-ray diffraction analysis. The anatase phased $TiO_2:0.01Eu^{3+}$ spheres exhibited a typical red emission under 463.5 nm wavelength. The diffused reflectance spectra displayed higher reflectance for rutile phase and lower for anatase phase. However, compared to the typically, combination of $YAG:Ce^{3+}$ yellow phosphor and blue LED chip, fabricated WLED, the light-extraction efficiency of WLED was improved to 80% when $TiO_2:0.01Eu^{3+}$ spheres were mixed with $YAG:Ce^{3+}$ phosphor in the fabrication process.

유기 발광 다이오드의 광 추출 효율 개선을 위한 다양한 광학기능구조의 적용

  • Kim, Yang-Du;Kim, Gwan;Heo, Dae-Hong;Lee, Heon
    • Ceramist
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    • v.21 no.1
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    • pp.64-79
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    • 2018
  • Recent years, OLEDs have been progressed intensively and been widely applied to Display and Lighting industry,Almost 100% internal quantum efficiency was achieved by developing new materials and structure optimization. However, external quantum efficiency was still low due to total internal reflection of light inside OLED devices and absorption of light at the surface of metal electrode. In order to improve external quantum efficiency of OLED devices, various kinds of optical functional structures were introduced to inside and outside of OLED devices to increase light extraction efficiency. In this paper, various efforts to apply optical functional structures in OLED devices were reviewed and way to improve light extraction efficency of OLED devices were discussed.

Design Rules for Core/Shell Nanowire Resonant Emitter

  • Kim, Da-Som;Kim, Sun-Kyung
    • Journal of the Korean Physical Society
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    • v.70 no.1
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    • pp.7-11
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    • 2017
  • We study design principles to boost the extraction of light from core/shell GaN nanowire optical emitters. A full-vectorial electromagnetic simulation reveals that the extraction efficiency of an emitter within a nanowire cavity depends strongly on its position; the efficiency becomes maximized as the emitter's location approaches the center of the structure. The total extraction of light is sinusoidally modulated by the nanowire diameter, which is directly correlated with optical resonances. The introduction of a conformal dielectric coating on a nanowire leads to a dramatic enhancement in the extraction efficiency, which results from an increase in side emission owing to an optical antenna effect. A simple high-refractive-index dielectric coating approximately doubles the total extraction efficiency of a nanowire LED. These numerical findings will be valuable in providing strategies for high-efficiency nanowire-based optical emitters.

Enhancement of Light Extraction from Transparent OLED Lighting Panels (투명 OLED 면광원 광 추출 향상 기술)

  • Park, June Buem;Shin, Dong-Kyun;Han, Seun Gjo;Park, Jong-Woon
    • Journal of the Semiconductor & Display Technology
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    • v.16 no.4
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    • pp.41-45
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    • 2017
  • We have investigated the light extraction efficiency of large-area OLED lighting panels with a microlens array (MLA) or external scattering layer (ESL) by ray tracing simulation. The application of MLA and ESL to transparent OLEDs (TOLEDs) with an auxiliary metal electrode is also studied. It is found that MLA shows higher light extraction efficiency, compared with ESL. However, we have demonstrated that ESL is more suitable for TOLEDs having dual-sided equal light emission. Namely, equal light emission from the front and rear surfaces of TOLED can be achieved by increasing the scattering particle density of ESL. To compensate for a loss in light emission induced by auxiliary metal electrode, we come out with an OLED structure partially covered with MLA at the outer surface of glass substrate, which is aligned with metal electrode. With this scheme, it is observed that the light extraction efficiency can be boosted more than 20% from opaque OLED and 50% from transparent OLED.

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