Design of a Structure for Optimized Optical Performance of a Full Colored Organic Light-Emitting Diode on a Parameter Space Map.

Bongsoon Kang,Ju-Hyeok Choi,Gi-Dong Lee,Seo-Yong Hyun,Ji-Ho Baek,Chang-Hee Lee

doi:10.3390/polym14030585

Bongsoon Kang, Ju-Hyeok Choi + Show 4 more

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https://doi.org/10.3390/polym14030585

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Journal: Polymers	Publication Date: Jan 31, 2022
License type: CC BY 4.0

Affiliation: Dong-A University, LG Corporation (South Korea)

Abstract

In general, optical properties of a top-emitting organic light-emitting diode (OLED) are dependent on the cavity effect of the OLED structure. Therefore, the optical path length of the many thin solid films in the OLED, which is strongly affected by the refractive index and thickness of each material, controls the cavity effect of the cell. In previous research, a parameter space method for optimizing the inorganic layer thickness of a red OLED structure was introduced to achieve the required bandwidth and peak wavelength. This is a simple method with high accuracy and can also be applied to red, green, and blue OLED structures. To design an OLED cell with a practical approach, however, the RGB OLED device requires the thickness of each inorganic layer and organic layer in all three R, G, and B OLED structures to be same. In this study, we applied the parameter space method to an RGB OLED device to find out and optimize the thickness of three inorganic parameters: Indium Tin Oxide (ITO), cathode, and capping layer (CPL) using the finite-difference time-domain (FDTD) method. The parameters ITO, cathode, and CPL were scanned from 18 to 21 nm, 5 to 100 nm, and 10 to 200 nm, respectively. The peak wavelength and bandwidth lines of the three spectral colors were placed on a map of the three inorganic layer thickness parameters to find the optimized points that can provide the desired optical characteristics with the same film thickness in the cell.

Highlights

The top emitting structure normally uses both the mirror and half-mirror structure for the resonance in the visible wavelength ranges, so the cavity effect of the many organic and inorganic films used in organic light-emitting diode (OLED) structures should be considered for their high optical properties [11,12,13]
We calculated the optimized optical path length n × d as functions of thickness of the inorganic layers the capping layer (CPL), the Cathode, and the Indium Tin Oxide (ITO) because change in the organic films can induce the deterioration of the electro-optical properties
The thickness ranges of ITO, Cathode, and CPL were set in the ranges of 13–22 nm, 5–100 nm, and 10–200 nm, respectively [20]

Summary

Introduction

White light from an OLED can normally be generated by composing three primary colors: red, green, and blue (RGB) [6,7,8,9]. The top emitting structure normally uses both the mirror and half-mirror structure for the resonance in the visible wavelength ranges, so the cavity effect of the many organic and inorganic films used in OLED structures should be considered for their high optical properties [11,12,13]. To obtain the required bandwidth and peak wavelength depending on the color of each structure, we normally change the optical length by changing the thickness of each layer in each RGB in all structures [14]

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Conclusion