Light Extraction Substrate for OLEDs via Refractive Index Optimization
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Solution Overview
Problem
The light extraction efficiency of OLED devices is limited due to total internal reflection and waveguide effects caused by differences in refractive indices between the organic light-emitting layer and the glass substrate, resulting in only about 20% of generated light being emitted, while 80% is lost, and internal light extraction layers are difficult to form and can cause light loss.
Innovation Solution
A light extraction substrate with a multilayer structure comprising a base substrate, light-scattering elements, a cover matrix layer with a higher refractive index, and a planarization layer, where at least one of these layers has a different refractive index, optimizing scattering efficiency to improve light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a planar waveguide structure is formed due to refractive index differences between layers, then the device structure is simple and easy to manufacture, but light extraction efficiency decreases significantly (only 20% of light is emitted)
Solution Approach 1:
The patent introduces a light extraction layer with specific refractive index parameters (1.7-1.8) and controlled thickness (200-400 nm) between the ITO anode and organic light-emitting layer. By changing the refractive index parameter of this intermediate layer, the patent optimizes light extraction efficiency while maintaining the simplicity of the overall device structure and manufacturing process.
2Loss of energy
If an internal light extraction layer is introduced to improve light extraction efficiency, then light extraction efficiency improves, but the device structure becomes more complex and formation becomes difficult
Solution Approach 1:
The light extraction layer serves multiple functions simultaneously: it acts as an optical layer for light extraction, provides structural support, and maintains electrical insulation. This multi-functionality allows the layer to improve light extraction efficiency without significantly increasing device complexity, as it integrates several roles into a single component rather than adding multiple separate layers.
3Loss of energy
If microlenses are disposed on the outer surface of the substrate to improve light extraction, then light extraction efficiency improves, but the manufacturing process becomes more complex
Solution Approach 1:
Instead of adding microlenses on the outer surface of the substrate (external light extraction), the patent inverts the approach by placing the light extraction layer internally between the ITO anode and the organic light-emitting layer. This internal placement simplifies manufacturing by integrating the light extraction function into an existing interface rather than requiring additional external microlens fabrication and alignment 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 optimized multilayer structure maximizes scattering efficiency, enhancing the light extraction efficiency of OLED devices by diversifying light paths and reducing light loss, thereby improving luminance.
Implementation Method 1
a number of light-scattering elements disposed on the base substrate; a cover matrix layer disposed on the base substrate to cover the number of light-scattering elements
Implementation Method 2
when a beam of light generated by the light-emitting layer is emitted at an angle greater than a critical angle, the beam of light may be totally reflected at the interface between a higher-refractivity layer, such as a transparent electrode layer acting as an anode, and a lower-refractivity layer, such as a glass substrate
Implementation Method 3
a cover matrix layer disposed on the base substrate to cover the number of light-scattering elements; at least one of the number of light-scattering elements, the cover matrix layer, and the planarization layer has a different refractive index
Data Source
AI summary
The present invention relates to a light extraction substrate for an organic light emitting element and, more specifically, to a light extraction substrate for an organic light emitting element that can enhance the light extraction efficiency of the organic light emitting element by optimizing a stack structure that can maximize scattering efficiency, and an organic light emitting element comprising the same. To this end, the present invention provides a light extraction substrate for an organic light emitting element and an organic light emitting element comprising the same, the light extraction substrate comprising: a base substrate; a plurality of light scattering objects arranged on the base substrate; a matrix layer formed on the base substrate to cover the plurality of light scattering objects; and a planarization layer that is formed on the matrix layer and of which the surface makes contact with an organic light emitting element, wherein at least one of the cover matrix layer, the planarization layer, and the light scattering objects has a different index of refraction.