OLED Substrate Planarization Layer for Light Extraction
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Solution Overview
Problem
Conventional OLED substrates suffer from low light extraction efficiency due to total internal reflection at the interface between the organic layer and the substrate, with only a small amount of light being emitted, primarily because of the mismatch in refractive indices between the organic layer, the electrode layers, and the substrate.
Innovation Solution
A substrate with a planarization layer having a refractive index of 1.8 to 2.5, formed using a binder and high refractive particles, which scatters and diffuses incident light, is used to improve light extraction efficiency. The planarization layer is formed on a base layer, which can be transparent or reflective, and includes scattering particles to enhance light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional substrate structure with ITO transparent electrode, organic layer, and glass substrate 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:
A planarization layer with refractive index of 1.8-2.5 is introduced as an intermediary between the organic layer (refractive index ~1.8) and the substrate (refractive index ~1.5). This intermediate layer acts as a refractive index bridge, reducing the abrupt refractive index mismatch at interfaces and minimizing total internal reflection, thereby improving light extraction efficiency without complicating the manufacturing process
Solution Approach 2:
The refractive index parameter of the substrate system is modified by introducing the planarization layer with a specific refractive index range (1.8-2.5). This parameter change optimizes the optical properties at the interface between the organic layer and substrate, enabling better light extraction while maintaining structural simplicity
2Stability of the object's composition
If the refractive index mismatch between organic layer, electrode layers, and substrate is maintained, then the conventional structure is preserved, but light is trapped at interfaces and only a small amount of light is emitted
Solution Approach 1:
The planarization layer serves as an optical intermediary that gradually transitions the refractive index from the organic layer to the substrate, reducing interface reflections and enabling more light to escape from the device while preserving the overall structural composition
3Loss of energy
If a planarization layer with high refractive index (1.8-2.5) and scattering particles is added to improve light extraction, then light emission is enhanced, but the device structure becomes more complex
Solution Approach 1:
The planarization layer performs multiple functions simultaneously: it provides surface planarization for device fabrication, acts as an optical intermediary to improve light extraction, and contains scattering particles to further enhance light emission. By combining these functions in a single layer, the design avoids adding separate components, thus limiting the increase in device complexity
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 enhances light extraction efficiency and prevents moisture and gas penetration, leading to improved performance and reliability of OLEDs by ensuring that more light is emitted and reducing the occurrence of dark spots.
Implementation Method 1
the planarization layer may have a light scattering property. That is, the planarization layer may scatter, diffuse, or refract incident light
Implementation Method 2
the planarization layer may scatter, diffuse, or refract incident light
Data Source
AI summary
Provided are a substrate for an organic electronic device (OED), an organic electronic system, and a light. The substrate capable of forming an OED ensuring excellent performances and reliability because it may have excellent performances including light extraction efficiency, permeation of moisture or a gas from an external environment may be inhibited, and growth of dark spots may be controlled may be provided.