High Refractive Index Substrate for Organic Electronic Devices
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Solution Overview
Problem
In organic electronic devices (OEDs), such as OLEDs, a significant amount of light is trapped due to the mismatch in refractive indices between the organic layer and the substrate, leading to low light extraction efficiency.
Innovation Solution
A substrate with a highly refractive layer having a refractive index of 1.8 to 2.5 is used, which includes scattering and highly refractive particles, along with a binder, to form a light scattering planarized layer that enhances light extraction efficiency by scattering and diffusing incident light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional substrate with glass and standard refractive index materials is used, then the device structure is simple and easy to manufacture, but light extraction efficiency is low due to total internal reflection at interfaces
Solution Approach 1:
The patent applies composite materials by incorporating a light scattering layer containing TiO2 particles (refractive index 2.6-2.9) into the substrate structure. This composite layer has a higher refractive index than both the organic layer (1.7-1.9) and the glass substrate (1.5), creating optimal refractive index gradient for light extraction while maintaining manufacturing feasibility through conventional coating processes
Solution Approach 2:
The patent changes the refractive index parameter of the substrate by introducing a light scattering layer with TiO2 particles. The layer's refractive index (2.6-2.9) is specifically selected to be higher than adjacent layers, fundamentally altering the optical parameters to reduce total internal reflection and improve light extraction efficiency from 1% to 20% or more
2Reliability
If a light scattering layer with high refractive index particles is added to improve light extraction efficiency, then light extraction efficiency is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The light scattering layer serves multiple functions simultaneously: it scatters light to improve extraction efficiency, provides a planarized surface for subsequent electrode and organic layer formation, and acts as a barrier layer. This multi-functionality reduces the need for additional separate layers, thereby limiting the increase in device complexity while achieving significant light extraction improvement
3Reliability
If the substrate structure is modified to improve light extraction, then light extraction efficiency is improved, but penetration of moisture and gas from external environment may increase
Solution Approach 1:
The light scattering layer acts as an intermediary barrier between the organic layer and the glass substrate. While its primary function is light scattering, it also serves as an additional protective layer that can incorporate barrier materials to prevent moisture and gas penetration, thus addressing both optical performance and environmental protection requirements
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 significantly improves light extraction efficiency, prevents moisture and gas penetration, and maintains device reliability by ensuring excellent performance and preventing dark spot growth.
Implementation Method 1
The highly refractive layer may be a light scattering planarized layer... and scatter, diffuse or refract incident light
Implementation Method 2
scatter or diffuse incident light
Implementation Method 3
the light generated in the organic emitting layer in the bottom emitting device is trapped at an interface between the organic layer and the first electrode layer or in the substrate due to a total internal reflection phenomenon
Data Source
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AI summary
Provided are a substrate for an organic electronic device (OED), an OED, and lighting. The substrate capable of forming an OED ensuring excellent performance and reliability because it has excellent performance including light extraction efficiency, penetration of moisture or a gas from an external environment is inhibited, and growth of dark spots is controlled may be provided.