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Organic Light-emitting Diode Using a High-refractive-index Scattering Layer for Higher Efficiency
New Physics: Sae Mulli 2016; 66: 540~544
Published online May 31, 2016;
© 2016 New Physics: Sae Mulli.

Hyemin JUNG, Seog GWAG*

Department of Physics, Yeungnam University, Gyeongsan 38541, Korea
Correspondence to:
Received December 14, 2015; Revised January 7, 2016; Accepted January 7, 2016.
cc This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
In this paper, we propose an organic light-emitting diode (OLED) structure with a high-refractive-index scattering layer to improve the OLED's external light efficiency. The light generated from the emitting layer is trapped partially in the hole transport layer (HTL) by total reflection, and the remaining light passes through the glass substrate and meets an air layer, where more light undergoes total reflection. Owing to these, OLED's efficiency is reduced by more than 50%. In order to decrease the reduction in the efficiency caused by the total reflection, we change the path of light to the air layer to a more normal direction. To change the light path, we use micro-sized SiO$_{2}$ particles which play the role of a kind of lens.  Furthermore, so as to change more clearly the path of the light, we use a high-refractive-index material (TiO$_{2}$) around the SiO$_{2}$ particles. When the efficiency of a conventional OLED is compared to that of the OLED with a high-refractive-index scattering layer for which the ratio of SiO$_{2}$ particle to the high-refractive-index material (TiO$_{2}$) is 1 : 3, the efficiency of the latter is found to be increased by about 24.12%.
PACS numbers: 78.60.Fi, 42.70.Jk, 78.20.Ci
Keywords: Organic light-emitting diode, Quantum efficiency, Total reflection, Scattering Layer

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