Organic EL Light Extraction via Composite Fine Particle Layer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Organic electroluminescence display devices suffer from low light extraction efficiency due to the high refractive index of their layers, leading to significant light loss through total reflection at the air interface, with existing methods providing insufficient improvements.
Innovation Solution
Incorporating a fine particle containing layer with organic resin material, a first fine particle, and a second fine particle of larger diameter in the optical path, where the refractive indices satisfy specific relationships, and using inorganic fine particles like TiO2, ZnO, or ZrO2, to enhance light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a diffusion layer with fine particles is provided adjacent to the transparent electrode, then light extraction efficiency is improved, but the improvement is insufficient
Solution Approach 1:
The patent uses a composite fine particle containing layer combining two types of inorganic fine particles with different refractive indices (first particle: 1.8-2.2, second particle: 2.3-2.7) dispersed in an organic resin material. This composite structure creates multiple refractive index differences that enhance light scattering and extraction efficiency beyond what single-particle systems achieve.
Solution Approach 2:
The patent applies local quality by creating a specialized fine particle containing layer with specific refractive index properties positioned between the organic compound layer and air. This layer has locally optimized refractive index (n1) that satisfies |n1-n2|<0.1, creating a gradient structure that progressively manages light extraction at different interfaces.
2Stability of the object's composition
If the refractive index of organic layers is high, then the device structure is stable, but total reflection at air interface increases causing light loss
Solution Approach 1:
The patent introduces a fine particle containing layer as an intermediary between the high refractive index organic compound layer (n2) and air. This intermediary layer has a refractive index (n1) that is carefully matched to the organic layer (|n1-n2|<0.1), allowing it to act as a transition zone that reduces total internal reflection while maintaining structural stability.
Solution Approach 2:
The patent changes the optical parameters by introducing inorganic fine particles with specific refractive indices into the organic resin material. By controlling the particle refractive indices (first: 1.8-2.2, second: 2.3-2.7) and their distribution, the layer's effective refractive index is optimized to reduce light loss while maintaining the stability of the underlying organic layer structure.
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 described configuration significantly improves light extraction efficiency by optimizing the refractive index relationships and using high refractive index inorganic fine particles, resulting in enhanced luminance and suitable application in both bottom and top emission type organic EL display devices.
Implementation Method 1
a refractive index n1 of the organic resin material into which the first fine particle is added and an average refractive index n2 of the organic compound layer satisfy a relationship |n1−n2|<0.1, and a refractive index n3 of the second fine particle satisfy a relationship n3−n1>0.2
Data Source
AI summary
The present invention provides an organic electroluminescence display device including an organic electroluminescence element which includes a transparent electrode, a counter electrode, and an organic compound layer provided between these electrodes, the organic compound layer including a light emitting layer, and a fine particle containing layer positioned in the optical path of light emitted from the light emitting layer, wherein the fine particle containing layer contains an organic resin material, a first fine particle, and a second fine particle having a weight average particle diameter greater than that of the first fine particle, wherein a refractive index n1 of the organic resin material into which the first fine particle is added and an average refractive index n2 of the organic compound layer satisfy a relationship |n1−n2|<0.25, and wherein the refractive index n1 and a refractive index n3 of the second fine particle satisfy a relationship n3−n1>0.2.