Reflective Electrode Concave-Convex Structure Diffracts Surface Plasmons
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Solution Overview
Problem
Organic electroluminescence (EL) display devices face inefficiencies in light extraction due to superfluous reflection and surface plasmon absorption, where light is trapped within the device, leading to reduced luminance and increased power consumption.
Innovation Solution
A light-emitting element configuration featuring a substrate with an interlayer insulating layer, a reflective electrode, and a concave-convex structure on the electrode surface to diffract surface plasmons, eliminating the need for an insulating layer on reflection structures and enhancing light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a reflective electrode with a flat surface is used, then light extraction is simple and device structure is simple, but surface plasmons are generated and light is absorbed, reducing light extraction efficiency
Solution Approach 1:
The patent applies curvature by forming a concave-convex structure on the reflective electrode surface. This curved surface structure diffracts surface plasmons that would otherwise be absorbed by a flat reflective electrode, converting the harmful absorption into useful light extraction while maintaining the simplicity of the reflective electrode configuration
2Loss of energy
If an insulating layer is added on the reflection structure to prevent superfluous reflection, then light extraction efficiency improves, but device complexity and manufacturing steps increase
Solution Approach 1:
The patent extracts the insulating layer from the reflection structure configuration. By removing the insulating layer that causes superfluous reflection, the reflective electrode can directly reflect light without the interference of additional layers, simplifying the device structure while maintaining high light extraction efficiency through the concave-convex surface geometry
3Productivity
If light is allowed to propagate within the organic EL element, then light extraction paths are created, but light is trapped by reflection at interfaces and attenuation occurs
Solution Approach 1:
The concave-convex structure on the reflective electrode creates multiple reflection paths with varying angles. This curved geometry prevents light from being trapped in single-direction propagation paths, reducing interface reflection losses and allowing light to escape more efficiently through multiple opportunities for extraction
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
The solution significantly improves light extraction efficiency by preventing surface plasmon absorption and reducing guided light attenuation, allowing more light to be emitted externally, thereby enhancing display performance and reducing power consumption.
Implementation Method 1
A concave-convex portion of a submicron order configured to diffract surface plasmons is provided on a surface of the reflective electrode
Implementation Method 2
one electrode out of the first electrode and the second electrode includes a reflective electrode
Implementation Method 3
organic EL elements utilizing the electroluminescence of organic materials
Data Source
AI summary
A light-emitting element includes at least a first trench portion having an indented shape within a single light-emitting region. In the first trench portion, a first electrode, an EL layer, and a second electrode are layered in this order and in contact with each other. One of the first electrode and the second electrode includes a reflective electrode, and concave-convex portions of the submicron order configured to diffract surface plasmons are provided on the surface of the reflective electrode on a side closer to the EL layer.