Light-Confining Layer Refractive Index for OLED Light Extraction
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Solution Overview
Problem
Current organic EL display devices face challenges in achieving high emission efficiency and color purity due to limitations in light extraction and resonance structures, particularly in the lateral direction, leading to reduced luminance and increased light loss.
Innovation Solution
The proposed solution involves a light-emitting element structure with a first electrode, a partition wall, a light-confining layer with a lower refractive index than the electroluminescence layer, and a second electrode, which creates a resonance structure that enhances light extraction efficiency by reflecting and amplifying light in both vertical and lateral directions, using materials like polyimide and fluorine-containing polymers to optimize refractive index differences and interference effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional light-emitting element structure is used, then the device is simple to manufacture, but light extraction efficiency is poor and emission efficiency is reduced
Solution Approach 1:
The patent introduces a light-confining layer as an intermediary component between the electroluminescence layer and the partition wall. This layer has a refractive index lower than the electroluminescence layer, creating a refractive index gradient that acts as an optical mediator to improve light extraction efficiency by reducing total internal reflection at the interfaces.
Solution Approach 2:
The patent optimizes the refractive index parameter by selecting materials for the light-confining layer with specifically lower refractive indices than the electroluminescence layer. This parameter change creates favorable optical conditions for light extraction while maintaining manufacturing feasibility using conventional organic EL materials and processes.
2Productivity
If light extraction is improved in the vertical direction, then emission efficiency increases, but light loss in the lateral direction increases
Solution Approach 1:
The patent applies local quality by creating different optical environments in different spatial regions. The light-confining layer is positioned specifically at the lateral interfaces where light loss occurs, providing localized optical confinement where needed while allowing efficient vertical light extraction in the emission region.
Solution Approach 2:
The patent addresses the lateral light loss problem by introducing a new spatial dimension - the light-confining layer extends laterally along the partition wall interface. This dimensional extension creates optical confinement in the lateral direction while preserving vertical extraction pathways, effectively managing light propagation in multiple dimensions.
3Illumination intensity
If a resonance structure is formed to adjust emission intensity, then emission color can be controlled, but light loss occurs and luminance is reduced
Solution Approach 1:
The patent optimizes the refractive index parameter of the light-confining layer to balance resonance effects and light extraction. By carefully selecting the refractive index to be lower than the electroluminescence layer but not excessively low, the patent achieves favorable resonance conditions for color control while minimizing extraction losses that would reduce luminance.
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 configuration significantly improves emission efficiency and color purity by minimizing light loss in the lateral direction, resulting in higher luminance and more efficient light extraction, while maintaining high emission efficiency in the front direction.
Implementation Method 1
A refractive index of the light-confining layer is lower than a refractive index of the electroluminescence layer
Implementation Method 2
a resonance structure is formed in a light-emitting element to allow light emission obtained from an emission layer to resonate, thereby adjusting emission intensity and emission color
Implementation Method 3
it is also possible to adjust an emission wavelength and increase emission intensity in a front direction by utilizing light-interference effects in or outside the light-emitting element
Data Source
AI summary
Provided is a light-emitting element including a first electrode, a partition wall covering an edge portion of the first electrode, a light-confining layer in contact with a side surface of the partition wall and the first electrode, an electroluminescence layer over the first electrode and in contact with the first electrode and the light-confining layer, and a second electrode over the electroluminescence layer. A refractive index of the light-confining layer is lower than a refractive index of the electroluminescence layer.