Light Extraction Substrate with Cracked Matrix for OLED Efficiency
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Solution Overview
Problem
The light extraction efficiency of OLED devices is limited due to the waveguide effect caused by different refractive indices between the glass substrate and the organic light-emitting layer, resulting in only about 20% of generated light being emitted, with the remaining 80% lost due to total internal reflection and waveguide modes.
Innovation Solution
A light extraction substrate is manufactured by forming cracks in a matrix layer using a sol-gel solution with scattering particles, which scatters light emitted by the OLED, improving the light extraction efficiency by diversifying the paths of emitted light. This is achieved by mixing a sol-gel solution containing a first metal oxide with scattering particles of a different refractive index, coating a base substrate, and firing the mixture to create a matrix layer with irregularly shaped voids and cracks that scatter light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a planar glass substrate is used, then the device structure is simple and easy to manufacture, but light extraction efficiency is low due to waveguide effect and total internal reflection
Solution Approach 1:
The patent applies porous materials by forming a matrix layer with controlled porosity (30-70%) containing scattering particles. The porous structure is created through sol-gel processing where the matrix layer is formed with voids and cracks that scatter light, reducing the waveguide effect and total internal reflection while maintaining ease of manufacture through a single-layer deposition process
Solution Approach 2:
The patent uses composite materials by combining a glass matrix with scattering particles (such as TiO2, SiO2, or ZrO2) having different refractive indices. This composite structure creates light scattering centers within the matrix layer, improving light extraction efficiency by disrupting the waveguide effect while maintaining the structural simplicity of a single substrate layer
2Loss of energy
If scattering particles are added to the matrix layer, then light scattering effect is enhanced, but the manufacturing process becomes more complex
Solution Approach 1:
The patent merges the scattering particle incorporation step with the matrix layer formation step by adding scattering particles to the sol-gel solution before deposition. This combining approach allows scattering particles to be uniformly distributed within the matrix layer during a single coating process, enhancing light scattering effect while avoiding additional manufacturing steps
Solution Approach 2:
The patent applies self-service by using the sol-gel process to automatically distribute and embed scattering particles within the matrix layer during formation. The sol-gel chemistry enables uniform particle incorporation and controlled porosity development through self-organization during drying and firing, reducing the need for complex external processing steps
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 method significantly improves light extraction efficiency, increasing it by up to 1.7 times compared to OLEDs without a light extraction layer, by creating a complexified light scattering structure within the matrix layer, thereby enhancing the outward emission of light.
Implementation Method 1
cracks allowing light emitted by an OLED to be scattered are formed in a matrix layer to further complexify or diversify paths of the emitted light
Implementation Method 2
preparing a mixture by mixing a sol-gel solution containing a first metal oxide and a number of scattering particles formed from a second metal oxide
Implementation Method 3
firing the mixture coating the base substrate to form a matrix layer on the base substrate
Implementation Method 4
about 80% of the light generated is lost due to a waveguide effect originating from different refractive indices... as well as by the total internal reflection originating from the difference in refractive indices between the glass substrate and ambient air
Data Source
AI summary
The present invention relates to a method for manufacturing a light extraction substrate for an organic light emitting diode, a light extraction substrate for an organic light emitting diode, and an organic light emitting diode comprising same, and more specifically, to a method for manufacturing a light extraction substrate for an organic light emitting diode, a light extraction substrate for an organic light emitting diode, and an organic light emitting diode comprising same, the method capable of complicating or diversifying the path of a light that is emitted by forming cracks on a matrix layer that can induce scattering of the light emitted from the organic light emitting diode, thereby further improving light extraction efficiency of the organic light emitting diode. To this end, provided in the present invention is the method for manufacturing the light extraction substrate for the organic light emitting diode, comprising: a mixture-preparing step of preparing a mixture by mixing a sol-gel solution containing a first metal oxide, and a plurality of scattering particles composed of a second metal oxide having a refractive index different from that of the first metal oxide; a mixture coating step of coating the mixture on a base substrate; and a mixture firing step of firing the mixture which has been coated to form, on the base substrate, the matrix layer comprising the first metal oxide and inside of which the scattering particles are dispersed, wherein in the mixture firing step, cracks that can induce scattering of the light emitted from the light emitting diode are formed on the matrix layer due to the difference in the coefficient of thermal expression (CTE) of the base substrate and the first metal oxide.