Translucent Substrate Scattering Layer for OLED Light Extraction
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Solution Overview
Problem
Current organic LED elements face issues with low light-extraction efficiency due to total reflection at the interface between the organic layer and the translucent electrode, leading to uneven surfaces that cause interelectrode short circuits and angular dependency of color, and existing solutions do not adequately address surface flatness and refractive index matching.
Innovation Solution
A translucent substrate with a scattering layer formed on a glass substrate, where the scattering layer consists of glass with a base material and dispersed scattering materials of different refractive indices, and a translucent electrode with a refractive index equal to or lower than the base material, ensuring a smooth surface and efficient light extraction by controlling the distribution and density of scattering materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a light scattering layer is provided on the substrate to improve light extraction, then light extraction efficiency is improved, but surface flatness deteriorates causing interelectrode short circuits
Solution Approach 1:
The patent employs a light scattering layer containing scattered light particles with controlled density and size distribution. The layer is designed with porosity and refractive index differences to scatter light effectively while maintaining surface flatness. The scattered particles are embedded in a matrix material that fills gaps and maintains a smooth outer surface, resolving the contradiction between light scattering performance and surface flatness.
Solution Approach 2:
The light scattering layer is designed with non-uniform particle distribution - higher particle density near the organic LED element interface for maximum light scattering, and lower density toward the outer surface to maintain flatness. This gradient structure allows the same layer to provide both strong light scattering capability and surface flatness, addressing the technical contradiction locally.
2Productivity
If glass particles are fixed to the substrate surface with adhesive to create light scattering, then light extraction is improved, but reliability deteriorates due to adhesive degradation
Solution Approach 1:
The patent replaces the degradable organic adhesive with an inorganic bonding mechanism. The glass particles are bonded to the substrate through inorganic adhesive layers or direct sintering, creating a stable, non-degradable connection that maintains light scattering performance over long periods without the reliability issues of organic adhesives.
Solution Approach 2:
The light scattering layer is constructed as a composite material system combining glass particles, inorganic adhesive or binder, and matrix material. This composite structure provides both the light scattering functionality of glass particles and the long-term stability of inorganic bonding materials, eliminating the reliability problems associated with organic adhesive degradation.
3Productivity
If the refractive index of the substrate is lowered to reduce total reflection, then light extraction is improved, but material selection becomes limited
Solution Approach 1:
The patent introduces a light scattering layer as an intermediary between the substrate and the organic LED element. This layer has a refractive index intermediate between the substrate and the organic layer, creating gradual refractive index transitions that reduce total reflection. This allows the use of standard substrate materials while still achieving improved light extraction through the intermediary scattering layer.
Solution Approach 2:
The light scattering layer is formulated as a composite material with tunable refractive index properties. By adjusting the composition, particle density, and matrix material of the composite layer, the refractive index can be optimized to match between the substrate and organic LED element, enabling improved light extraction while maintaining flexibility in substrate and electrode material selection.
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 to up to 80% of emitted light, reduces angular dependency of color, and provides a stable and long-lasting organic LED element with a smooth surface, preventing interelectrode short circuits and maintaining high-intensity performance.
Implementation Method 1
the scattering layer consists of glass with a base material and dispersed scattering materials of different refractive indices
Implementation Method 2
a scattering layer formed on a glass substrate, where the scattering layer consists of glass with a base material and dispersed scattering materials of different refractive indices
Implementation Method 3
light which tries to enter the glass substrate at a shallow angle is reflected by total reflection in an organic layer direction
Data Source
AI summary
The present invention provides an organic LED element in which the extraction efficiency is improved up to 80% of emitted light. Further, the invention relates to an electrode-attached translucent substrate having a translucent substrate, a scattering layer formed over the glass substrate and containing a base material having a first refractive index for at least one wavelength of wavelengths of emitted light of an organic LED element and a plurality of scattering materials positioned in the base material and having a second refractive index different from that of the base material, and a translucent electrode formed over the scattering layer and having a third refractive index equal to or lower than the first refractive index, in which distribution of the scattering materials in the scattering layer decreases from the inside of the scattering layer toward the translucent electrode.