Refraction Conversion Layer for OLED Light Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Organic light-emitting devices suffer from reduced light efficiency due to total internal reflection at interfaces with different refractive indices, leading to inefficient light emission in arbitrary directions without directivity.
Innovation Solution
A light-emitting device structure featuring a substrate, a first electrode with a higher refractive index, a refraction conversion layer with sequentially formed layers of varying refractive indices, and a second electrode, along with an organic emissive layer, is designed to reduce total internal reflection and enhance light extraction efficiency. The refraction conversion layer includes layers with progressively lower refractive indices from the first electrode to the substrate, and a semi-transmissive reflection layer can be added to form an optical resonance structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If light is emitted in an arbitrary direction according to uniform angular distribution, then the organic light-emitting device can emit light without directional constraints, but a considerable number of photons do not arrive at the observer due to total internal reflection, decreasing light emitting efficiency
Solution Approach 1:
The patent introduces a refraction conversion layer as an intermediary between the organic emissive layer and the external environment. This layer has a refractive index that is intermediate between the high refractive index of the organic emissive layer and the low refractive index of air, thereby reducing the refractive index difference and minimizing total internal reflection. This mediator enables light to escape in arbitrary directions while improving light extraction efficiency.
Solution Approach 2:
The patent changes the refractive index parameter by introducing a refraction conversion layer with a specific refractive index value that is lower than the organic emissive layer but higher than air. This parameter change reduces the refractive index contrast at the interface, thereby reducing total internal reflection and improving light extraction efficiency while maintaining omnidirectional emission characteristics.
2Loss of energy
If a refraction conversion layer with intermediate refractive index is introduced between the organic emissive layer and the external environment, then total internal reflection is reduced and light extraction efficiency is improved, but the device structure becomes more complex
Solution Approach 1:
The patent applies local quality by introducing the refraction conversion layer only at specific locations where light extraction is needed, rather than uniformly throughout the entire device. The layer is positioned between the organic emissive layer and the external environment, specifically at the interface where total internal reflection occurs, thereby improving light extraction efficiency without unnecessarily increasing overall device complexity.
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 reduces total internal reflection, improves light extraction efficiency, and minimizes color shift at different viewing angles, thereby enhancing the overall performance of light-emitting devices and organic light-emitting display apparatuses.
Implementation Method 1
total internal reflection inside the organic light-emitting device
Implementation Method 2
refraction conversion layer including a first layer having a refractive index greater than the refractive index of the first electrode, a second layer having a refractive index smaller that that of the first layer, and a third layer having a refractive index smaller than the refractive index of the second layer
Data Source
AI summary
A light emitting device includes: a substrate; a first electrode on the substrate, the first electrode including a light-transmissive material having a refractive index greater than a refractive index of the substrate; a refraction conversion layer between the substrate and the first electrode, the refraction conversion layer including a first layer having a refractive index greater than the refractive index of the first electrode, a second layer having a refractive index smaller than the refractive index of the first layer, and a third layer having a refractive index smaller than the refractive index of the second layer, wherein the first layer, the second layer, and the third layer are sequentially formed in a direction from the first electrode toward the substrate; a second electrode facing the first electrode; and an organic emissive layer between the first electrode and the second electrode.