High Refractive Index OLED Substrate Light Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Organic electroluminescence devices (OLEDs) suffer from low light extraction efficiency due to reflection at interfaces between layers with different refractive indices, with only about 20% of emitted light being extracted externally, limiting their performance in displays and illumination applications.
Innovation Solution
An OLED structure is developed with a support substrate, a high refractive index layer between the substrate and the first transparent electrode, and a reflection mirror layer on the opposite side, along with a light transmissive charging layer, to enhance light extraction efficiency. The high refractive index layer is formed using a glass paste composition with glass frit, and the structure includes a protection layer to reduce light loss and improve manufacturing yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a diffractive lattice structure or lens structure is provided on the substrate to improve light extraction efficiency, then light extraction efficiency is improved, but manufacturing complexity increases due to the need for fine structures
Solution Approach 1:
The patent changes the refractive index parameter of the substrate layer to improve light extraction efficiency. By using a substrate with a refractive index of 1.7 or more (such as alumina with n=1.7-2.0), the patent achieves high light extraction efficiency without requiring complex fine structures like diffractive lattices or lenses, thus resolving the contradiction between improving light extraction and maintaining manufacturing simplicity
Solution Approach 2:
The patent applies local quality by creating a microlens array structure on the light-emitting surface. These microlenses are locally formed only where light extraction is needed, with each microlens having a specific curvature radius (0.5-5.0 μm) that is optimized for light extraction. This localized approach improves light extraction efficiency without making the entire device structure complex
2Loss of energy
If the refractive index of the substrate is increased to improve light extraction efficiency, then light extraction efficiency is improved, but the refractive index matching becomes more difficult with conventional substrates
Solution Approach 1:
The patent uses composite materials to achieve the required high refractive index. Specifically, it employs alumina (Al2O3) as the substrate material, which has a refractive index of 1.7-2.0, and combines it with organic light-emitting layers. This composite approach allows achieving high light extraction efficiency while using materials that are compatible with conventional OLED manufacturing processes
Solution Approach 2:
The patent changes the refractive index parameter of the substrate to 1.7 or more, which is higher than conventional glass substrates (n≈1.5). By selecting materials like alumina with specifically high refractive indices, the patent improves light extraction efficiency while maintaining compatibility with standard OLED device architectures and manufacturing processes
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 proposed structure significantly increases light extraction efficiency, improving the external light output by reducing total reflection and plasmon loss, while maintaining the reliability and stability of the OLED device.
Implementation Method 1
having a light dispersion portion for dispersing incident light from the organic light-emitting layer
Implementation Method 2
A diameter of an air bubble existing in the high refractive index layer may be less than or equal to 1/10 of a thickness of a layer adjacent to the first transparent electrode among layers forming the high refractive index layer
Data Source
AI summary
An organic electroluminescence device includes a support substrate, a first transparent electrode on the support substrate, an organic light-emitting layer on the first transparent electrode, a second transparent electrode on the organic light-emitting layer, and a high refractive index layer arranged between the support substrate and the first transparent electrode, having at least one layer having a refractive index greater than or equal to a refractive index of the support substrate, having a light dispersion portion for dispersing incident light from the organic light-emitting layer, and having a planar surface contacting the first transparent electrode.