Porous OLED Substrate Light Extraction
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Solution Overview
Problem
Organic light-emitting devices (OLEDs) suffer from low light extraction efficiency due to waveguide effects caused by refractive index differences between the glass substrate and the organic light-emitting layer, leading to color shift issues when viewed from different angles, and existing solutions like low-index grids and convex-concave structures face challenges such as leakage current and processing difficulties.
Innovation Solution
A porous layer with a lower refractive index than the glass substrate is formed on the OLED substrate, featuring patterns like semi-oval, trapezoid, or wedge shapes, which disturbs the waveguide mode and enhances light extraction while reducing color shift by promoting color mixing, and is created using lithography or metal nano particle patterning techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a planar glass substrate is used, then the manufacturing process is simple, but light extraction efficiency is low due to waveguide effects
Solution Approach 1:
The patent applies a porous layer with porous structures formed on the glass substrate. The porous structures have refractive indices lower than the glass substrate, disrupting the waveguide mode and enhancing light extraction efficiency while maintaining manufacturing simplicity through lithography or metal nano particle patterning techniques.
Solution Approach 2:
The patent changes the refractive index parameter by introducing a porous layer with lower refractive index than the glass substrate. This parameter change disrupts the total internal reflection condition and waveguide mode, thereby improving light extraction efficiency without complicating the manufacturing process.
2Loss of energy
If a low-index grid is formed on the anode, then light extraction efficiency is enhanced, but leakage current occurs and processing becomes difficult
Solution Approach 1:
The patent extracts the low-index structure from the anode interface and relocates it to the substrate surface. By forming the porous layer on the glass substrate rather than on the anode, the patent avoids the leakage current issue while maintaining the light extraction enhancement benefit.
Solution Approach 2:
The patent introduces the porous layer as an intermediary structure between the glass substrate and the OLED stack. This intermediary porous layer with lower refractive index serves as the light extraction enhancement mechanism without directly contacting the anode, thereby avoiding leakage current problems.
3Loss of energy
If a convex-concave structure is formed on the substrate, then light extraction is improved, but leakage current increases due to sharp portions
Solution Approach 1:
The patent uses a porous layer with controlled porous structures instead of sharp convex-concave features. The porous structures provide gradual refractive index transitions and avoid sharp portions that would concentrate current, thereby improving light extraction while maintaining low leakage current.
4Stability of the object's composition
If light is trapped by total internal reflection, then viewing angle stability is improved, but color shift increases
Solution Approach 1:
The patent changes the refractive index parameter at the substrate surface by introducing the porous layer. This parameter change modifies the critical angle for total internal reflection and disrupts the waveguide mode, enabling better color uniformity across viewing angles while maintaining manufacturing simplicity.
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 porous layer increases light extraction efficiency, simplifies processing, reduces leakage current, and minimizes color shift by altering the light direction at critical angles, thereby improving the overall performance of OLEDs.
Implementation Method 1
A porous layer with a lower refractive index than the glass substrate is formed on the OLED substrate, featuring patterns like semi-oval, trapezoid, or wedge shapes, which disturbs the waveguide mode and enhances light extraction
Implementation Method 2
about 80% of the light is lost by a waveguide effect originating from the difference in the refractive index between a glass substrate 10 and an organic light-emitting layer 30 and by a total internal reflection originating from the difference in the refractive index between the glass substrate 10 and the air
Data Source
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AI summary
A substrate for an organic light-emitting device (OLED) with enhanced light extraction efficiency, a method of manufacturing the same and an OLED having the same, in which the light extraction efficiency is enhanced, thereby reducing the phenomenon of color shift in which color changes depending on the position of a viewer within the viewing angle. The transparent substrate used in an OLED includes an anode, an organic light-emitting layer and a cathode which are stacked on each other, the transparent substrate comprising a porous layer pattern in at least one portion of one surface thereof that adjoins the organic light-emitting device, a refractive index of the porous layer being smaller than a refractive index of the transparent substrate, the cross sectional shape of the porous layer pattern being selected from the group consisting of a semi-oval, a trapezoid and a wedge.