Refractive Index Barrier Layer for OLED Light Extraction
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Solution Overview
Problem
Existing display devices using organic electroluminescent elements face reduced light extracting efficiency due to unintended reflection at interfaces between layers with different refractive indices, leading to decreased luminance.
Innovation Solution
A light emitting element is designed with a recess structure where a barrier layer, formed as a laminate of layers with different refractive indices, is placed between a second electrode and a second member with a higher refractive index than the first member, controlling the refractive index to minimize reflection and enhance light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If layers with different refractive indices are stacked to form the light emitting element, then the light emitting structure can be formed, but unintended light reflection occurs at interfaces between layers
Solution Approach 1:
A barrier layer with intermediate refractive index is introduced between the second electrode (high refractive index) and the second member (low refractive index). This intermediary layer reduces the refractive index difference at the interface, thereby suppressing unintended light reflection and improving light extraction efficiency.
Solution Approach 2:
The refractive index parameter of the barrier layer is specifically controlled to be between the refractive indices of the second electrode and the second member. By adjusting this parameter, the optical impedance mismatch is reduced, minimizing reflection at the interface between layers with different refractive indices.
2Object-generated harmful factors
If a barrier layer with intermediate refractive index is introduced, then light reflection is suppressed, but the device structure becomes more complex
Solution Approach 1:
The barrier layer is segmented into a laminate structure consisting of multiple sub-layers with different materials and refractive indices. This segmentation allows precise control of the overall refractive index while maintaining suppression of light reflection, and can also provide additional functional benefits such as stress management and adhesion improvement.
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 effectively suppresses unintended light reflection, improving light extracting efficiency and luminance by optimizing the refractive index of the barrier layer between the second electrode and the second member.
Implementation Method 1
a barrier layer formed as a laminate of a plurality of layers having different refractive indices and having, as the entire laminate, a refractive index between the refractive index of the second electrode and the refractive index of the second member is disposed
Implementation Method 2
light emitted from the light emitting element may be reflected a plurality of times at interfaces between various layers
Data Source
AI summary
A light emitting element and corresponding display device with improved light extracting efficiency are disclosed. In one example, a light emitting element includes a first electrode with a first member disposed on both sides to form a recess structure with the first electrode as a bottom. An organic light emitting layer is disposed along the recess structure on the first electrode and the first member, and a second electrode is disposed on the organic light emitting layer. A second member having a higher refractive index than the first member is disposed on the second electrode so as to embed the recess structure. Between the second electrode and the second member, a laminate barrier layer is formed of layers having different refractive indices and having, as the entire laminate, a refractive index between the refractive index of the second electrode and the refractive index of the second member.