Porous Light Extraction Substrate for OLED Efficiency
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Solution Overview
Problem
The light extraction efficiency of OLEDs is limited due to total reflection at the interface between higher and lower refractivity layers, resulting in only about 25% of emitted light being outwardly emitted, with the remaining 75% being lost.
Innovation Solution
A light extraction substrate with a base substrate and a light extraction layer featuring a plurality of pores formed on the base substrate, which can be made of glass frit, is used to scatter light and improve extraction efficiency. The light extraction layer can be formed by melting and pulverizing glass to create a frit powder, mixing it with an organic solvent and binder, applying it via screen printing, and firing to create hemispherical beads with pores.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a typical OLED structure with flat interface between transparent electrode and substrate is used, then the device structure is simple and easy to manufacture, but total reflection occurs at the interface causing low light extraction efficiency (only about 25% of light is emitted outward)
Solution Approach 1:
The patent introduces a light extraction layer containing a plurality of pores with the substrate as the bottom surface. These pores scatter light that would otherwise undergo total reflection at the interface, enabling more light to escape. The porous structure increases light extraction efficiency while maintaining ease of manufacture through a simple firing process that forms the pores in-situ.
Solution Approach 2:
The patent employs hemispherical beads as the light extraction layer, where each bead has a curved spherical surface. This curvature helps to scatter light at multiple angles, reducing total reflection effects. The hemispherical shape is formed naturally during the firing process of the glass frit paste, combining manufacturing simplicity with optical performance improvement.
2Loss of energy
If light extraction efficiency is improved by adding complex structures, then more light can be extracted, but the device structure becomes more complex and manufacturing difficulty increases
Solution Approach 1:
The patent merges the light extraction function with the existing substrate structure by forming the light extraction layer directly on the substrate through a firing process. The pores are formed within the glass frit matrix that is already part of the device structure, eliminating the need for separate light extraction components and reducing overall device complexity.
Solution Approach 2:
The light extraction layer is formed using glass frit paste that is applied as a thin layer and then fired to create the porous structure. This approach uses simple, inexpensive materials and a straightforward firing process rather than complex precision manufacturing techniques, making the solution cost-effective and easy to manufacture.
3Loss of energy
If more light is extracted from the OLED, then luminous efficiency improves, but this requires additional energy input or increases operating current
Solution Approach 1:
The patent converts the harmful effect of total reflection (which causes light loss) into a beneficial scattering effect. The pores and curved surfaces of the light extraction layer cause light that would have been totally reflected to instead scatter and escape, turning the previously wasted light into useful extracted light without requiring additional energy input or increased operating current.
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 substrate enhances light extraction efficiency, allowing OLEDs to operate at lower currents, reduce power consumption, and increase luminance by scattering light through the pores, while maintaining a flat surface for internal application.
Implementation Method 1
The light extraction layer has therein a plurality of pores which is formed on the base substrate such that the base substrate forms a bottom surface of the plurality of pores
Implementation Method 2
forming a frit powder by melting and pulverizing a glass
Implementation Method 3
firing the printed frit paste to form a light extraction layer in which a plurality of pores having the base substrate as a bottom surface is formed
Data Source
AI summary
An organic light-emitting device (OLED) which can improve the light extraction efficiency of the OLED, a method of fabricating the same and an OLED including the same. The light extraction substrate is disposed on one surface of an OLED through which light generated from the OLED is emitted outward, and includes a base substrate and a light extraction layer formed on the base substrate. The light extraction layer has therein a plurality of pores which is formed on the base substrate such that the base substrate forms a bottom surface of the plurality of pores.