Organic Electroluminescence Element Light Extraction
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Solution Overview
Problem
Existing organic electroluminescence elements suffer from low light emission efficiency due to light being confined within the device, with only 20% of emitted light escaping, and there is a lack of clear optical design principles for incorporating a light scattering region on the substrate to enhance light extraction.
Innovation Solution
The organic electroluminescence element is designed with a light transmissive electrode, a light reflective electrode, an organic light emission layer, and a light scattering layer, where the light scattering layer is positioned between the light transmissive electrode and the substrate, with the distance between the luminous point and the light reflective electrode determined by a specific formula to optimize light extraction, increasing the light flux and photon number emitted.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a light scattering region is disposed on the outer surface of the substrate, then the light extraction efficiency is improved, but the device structure becomes more complex
Solution Approach 1:
The patent combines the light scattering region with the substrate by disposing it on the outer surface of the substrate, merging two functional elements into a integrated structure. This reduces the need for separate light scattering components while maintaining enhanced light extraction efficiency.
Solution Approach 2:
The light scattering region is positioned on the outer surface of the substrate, utilizing the surface dimension to achieve light scattering functionality without adding thickness to the device. This dimensional approach allows light extraction enhancement without increasing device complexity in the vertical direction.
2Productivity
If the distance between the luminous point and the light reflective electrode is optimized according to the specific formula, then the light flux and photon number are increased, but the manufacturing precision requirements are heightened
Solution Approach 1:
The patent provides specific formulas that define the optimal distance d as a function of wavelength λ and refractive index n, allowing manufacturers to adjust the distance parameter based on the specific optical characteristics of the device. This parameter-based approach enables optimization of light flux while providing clear manufacturing guidelines.
Solution Approach 2:
The patent calculates and specifies the optimal distance d before the actual device assembly, allowing manufacturers to pre-determine the correct spacing between the luminous point and light reflective electrode. This preliminary calculation approach reduces manufacturing complexity by providing clear target values for the distance parameter.
3Loss of energy
If the light scattering layer is positioned between the light transmissive electrode and the substrate, then the light extraction efficiency is improved, but the device thickness increases
Solution Approach 1:
The light scattering layer is positioned on the outer surface of the substrate, utilizing the surface area dimension to achieve light scattering functionality without significantly increasing the vertical thickness of the device. This approach allows light extraction enhancement while maintaining a compact device profile.
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 design significantly increases the light flux and photon number emitted from the organic electroluminescence element, improving light extraction efficiency and addressing the limitations of previous designs by ensuring a higher percentage of light is directed outside the device.
Implementation Method 1
a light scattering layer (7), and a light transmissive substrate (6), wherein the light scattering layer (7) is disposed on the light transmissive substrate (6)
Implementation Method 2
The light reflective electrode is disposed on the first surface of the organic light emission layer
Implementation Method 3
the organic electroluminescence element comprises a light transmissive electrode (1), a light reflective electrode (2), an organic light emission layer (5)
Data Source
AI summary
The electroluminescence element comprises the light-reflective-electrode separated from the luminous point by distance “d” satisfying the following formula.nd=a×λ4{2m+ϕπ}whereinϕ=tan-1{2(n1k2-n2k1)n12-n22+k12-k22}λ is a wavelength of the light from the light emission layer. N is a refractive index of a certain layer between the luminous point and the light-reflective-electrode at λ. n1 and k1 is a refractive index and the extinction coefficient of the certain layer at λ. n2 and k2 is a refractive index and the extinction coefficient of the light-reflective-electrode at λ. m is 0 or 1. When “m” is 0, “a” satisfies the following formula.−1.17×norg/nEML+1.94≦a≦−0.16×norg/nEML+2.33When “m” is 1, “a” satisfies the following formula.0.28×norg/nEML+0.75≦a≦2.85×norg/nEML−1.23norg is a refractive index of a predetermined layer in contact with the light emission layer to be located on the same side as the light-reflective-electrode at λ. nEML is a refractive index of the light emission layer at λ.