OLED Light Extraction via High Refractive Index Interlayer
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Solution Overview
Problem
Conventional organic electroluminescent display devices suffer from low light coupling efficiency due to total internal reflection at the ITO/glass and glass/air interfaces, and existing methods to improve this, such as using diffraction gratings, face challenges in production and result in reduced luminous efficiency and durability due to surface roughness and unevenness.
Innovation Solution
The introduction of a diffraction grating layer with alternating high and low refractive gratings, along with a high refractive layer interposed between the diffraction grating and the first electrode, minimizes voids and unevenness, prevents optical losses, and focuses light distribution, thereby enhancing light coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a diffraction grating is introduced to improve light coupling efficiency, then light extraction is enhanced, but production difficulty increases and surface roughness deteriorates
Solution Approach 1:
The patent changes the refractive index parameter by introducing a high refractive index layer (n>2.0) between the diffraction grating and the organic layer. This parameter modification enables the system to achieve improved light coupling efficiency without requiring complex diffraction grating structures, thereby simplifying production while maintaining energy extraction performance.
Solution Approach 2:
The patent introduces a high refractive index layer as an intermediary component between the diffraction grating and the organic light-emitting layer. This intermediary layer mediates the optical interaction, enhancing light extraction efficiency while avoiding the need for complex direct diffraction grating patterns on the organic layer, thus simplifying the manufacturing process.
2Loss of energy
If a diffraction grating is introduced to improve light coupling efficiency, then light extraction is enhanced, but surface roughness increases and durability decreases
Solution Approach 1:
The patent modifies the refractive index parameter by introducing a high refractive index layer (n>2.0) that provides optical enhancement without requiring physical surface roughness. This allows the system to achieve improved light coupling efficiency while maintaining a smooth organic layer surface, thereby preserving device durability and reliability.
Solution Approach 2:
The high refractive index layer serves as an intermediary that provides the optical function of light extraction enhancement without requiring the organic layer itself to have rough surface features. This protects the organic layer from degradation associated with surface roughness while maintaining improved light coupling efficiency.
3Loss of energy
If a high refractive layer is interposed between the diffraction grating and the first electrode, then light distribution is focused and optical losses are prevented, but device complexity increases
Solution Approach 1:
The patent changes the refractive index parameter by introducing a high refractive index layer (n>2.0) that simultaneously addresses multiple optical issues: preventing optical losses and focusing light distribution. This single parameter change achieves multiple optical optimization goals without requiring multiple complex components or structures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly increases light coupling efficiency by reducing reflectance at the substrate-electrode interface and improving light distribution within the diffraction grating layer, leading to enhanced luminance and durability of the organic electroluminescent display device.
Implementation Method 1
The introduction of a diffraction grating layer with alternating high and low refractive gratings... significantly increases light coupling efficiency
Implementation Method 2
a high refractive layer interposed between the diffraction grating and the first electrode... focuses light distribution, thereby enhancing light coupling efficiency
Implementation Method 3
organic electroluminescent display devices are self-emissive display devices that emit light by electrically exciting a fluorescent organic compound
Data Source
AI summary
An organic electroluminescent display device and a method of producing the same are provided. The organic electroluminescent display device includes: a substrate; and an organic electroluminescent unit formed on a surface of the substrate and including a first electrode, an organic layer and a second electrode sequentially deposited on the substrate, in which the organic electroluminescent display device includes a diffraction grating layer having low refractive gratings and high refractive gratings alternately formed parallel to the substrate, and a high refractive layer formed on the diffraction grating layer interposed between the substrate and the first electrode. According to the organic electroluminescent display device, the light coupling efficiency can be increased due to minimized voids and unevenness generated in the formation of a diffraction grating layer, optical losses due to a first electrode can be prevented due to a high refractive layer interposed between the diffraction grating layer and the first electrode to focus light distribution on the high refractive layer, and the light coupling efficiency can be maximized due to increased light distribution in the diffraction grating layer.