OLED Light Extraction via Microlens Array and High Refractive Index Layer
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Solution Overview
Problem
Current organic light emitting devices suffer from low light extraction efficiency due to total reflection at the interface between the transparent electrode and the transparent substrate, resulting in only a small percentage of generated light being emitted outside the device, with most being confined or absorbed as heat.
Innovation Solution
An organic light emitting device with a high refractive index layer and a light reuse pattern is introduced, which includes a substrate, a first electrode, one or more organic material layers with a light emitting layer, and a second electrode, where the high refractive index layer is positioned on at least one side of the first electrode and the second electrode, and the light reuse pattern enhances light extraction by reusing light that would otherwise be total reflected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a planar structure with transparent electrode and substrate is used, then the device structure is simple and manufacturing is easy, but light extraction efficiency is low due to total reflection at interfaces
Solution Approach 1:
The patent introduces a microlens array layer that adds a new dimensional element (lens curvature and focal points) to the otherwise planar structure. This dimensional change allows light to be focused and extracted at specific points, overcoming the total reflection limitation of flat interfaces while maintaining manufacturing feasibility through batch fabrication processes.
Solution Approach 2:
The microlens array acts as an intermediary component between the organic light emitting layer and the external environment. These lenses mediate the light extraction process by refracting and focusing light that would otherwise be trapped by total reflection, thereby improving light extraction efficiency without requiring fundamental changes to the electrode-substrate structure.
2Illumination intensity
If the refractive index of the organic material layer is 1.7, then the material properties are suitable for light emission, but only about 17% or less of generated light can be emitted to the outside due to total reflection
Solution Approach 1:
The patent employs microlenses with curved surfaces instead of flat interfaces. The spherical curvature of the lenses creates varying refraction angles that enable light to escape at angles beyond the critical angle, effectively overcoming the total reflection problem inherent in planar interfaces with high refractive index materials.
Solution Approach 2:
The patent changes the optical parameters at the light extraction interface by introducing microlenses with specific refractive indices and curvature radii. This parameter modification allows light to be extracted efficiently despite the high refractive index (1.7) of the organic material layer, transforming the optical field distribution to maximize light emission.
3Reliability
If total reflection occurs at the interface between transparent electrode and substrate, then light is confined in the device, but this results in heat generation and reduced device stability
Solution Approach 1:
The patent converts the harmful effect of total reflection (trapped light becoming heat) into a beneficial outcome. By using microlenses to extract light before it causes heating, the design transforms what would be wasted energy into useful light emission, thereby reducing heat generation and improving device stability and reliability.
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 maximizes light extraction efficiency by reusing light that would be confined within the device, significantly increasing the amount of light emitted outside, while minimizing heat generation and improving the device's stability and manufacturing feasibility.
Implementation Method 1
total reflection occurs at the interface between the glass substrate and the transparent anode
Implementation Method 2
light that is generated in the light emitting layer may travel through the following different two paths by a difference in refractive index in each layer
Data Source
AI summary
The present invention relates to an organic light emitting device that has a structure which is capable of maximally extracting light generated in the organic light emitting device to the outside. In detail, the organic light emitting device according to the present invention is characterized in that the organic light emitting device includes a high refractive index layer or an electrode that includes a light reuse pattern.