OLED Light Extraction Structure with Micro-Structures
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Solution Overview
Problem
Organic light-emitting diodes (OLEDs) have high internal quantum efficiency but low external quantum efficiency due to significant light being confined within the device, necessitating a solution to enhance light extraction.
Innovation Solution
An organic light-emitting module comprising a light-transmissive substrate with a refractive index greater than 1.5, a light extracting structure with surface micro-structures, and a transparent carrying board, where the minimum distance between the light extracting structure and the carrying board is less than or equal to 125 μm, facilitating efficient light transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If light is emitted from the emissive layer in OLED, then internal quantum efficiency is high, but external quantum efficiency remains low due to light confinement
Solution Approach 1:
The patent divides the light extraction function into multiple components: the light-transmissive substrate with micro-structures, the encapsulation layer, and the specific spacing arrangement. This segmentation allows each component to contribute to reducing light confinement - the substrate micro-structures scatter waveguide modes, the encapsulation layer provides additional extraction interfaces, and the spacing prevents complete total internal reflection, collectively improving external quantum efficiency while maintaining high internal quantum efficiency
Solution Approach 2:
The patent introduces an intermediary space between the light extracting structure and the transparent carrying board (with minimum distance ≤125 μm). This intermediary region acts as a mediator that allows light to escape from the high-index organic materials through multiple interfaces before reaching the final substrate, reducing both waveguide mode confinement and interface total reflection without requiring direct contact between components
2Illumination intensity
If a transparent substrate with high refractive index (>1.5) is used, then light transmission is improved, but waveguide mode confinement increases
Solution Approach 1:
The patent applies local quality modification by creating micro-structures (such as protrusions or patterns) on specific regions of the light-transmissive substrate. These localized structural variations change the refractive index distribution at specific points, allowing light to be extracted from waveguide modes at particular locations while maintaining high overall light transmission through the substrate. The micro-structures create local extraction zones that convert confined waveguide light into extractable rays
3Productivity
If the distance between light extracting structure and carrying board is reduced, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
The patent optimizes the spacing dimension between the light extracting structure and the transparent carrying board to be ≤125 μm. This specific dimensional constraint in the vertical dimension (z-direction) creates an optimal extraction zone without requiring complex lateral arrangements. By controlling the distance in this specific dimension, the patent achieves high light extraction efficiency through a simple vertical stacking architecture, avoiding the need for complex lateral positioning or additional alignment mechanisms
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 solution increases the brightness of the OLED module by reducing waveguide mode confinement and interface total reflection, resulting in a 1.3 times improvement in external quantum efficiency.
Implementation Method 1
a large amount of light is confined inside the OLED. This is because a large amount of light is confined inside organic materials and a transparent substrate
Implementation Method 2
increases the brightness of the OLED module by reducing waveguide mode confinement and interface total reflection
Implementation Method 3
The light-transmissive substrate has an index of refraction greater than 1.5
Data Source
AI summary
An organic light-emitting module including a light-transmissive substrate, a light extracting structure, a first electrode, an organic light-emitting stack, a second electrode, and a transparent carrying board is provided. The light-transmissive substrate has an index of refraction greater than 1.5 and has a first surface and a second surface opposite to the first surface. The light extracting structure is disposed at the first surface. The first electrode is disposed on the second surface of the light-transmissive substrate. The organic light-emitting stack is disposed on the first electrode. The second electrode is disposed on the organic light-emitting stack. The transparent carrying board is connected with the light extracting structure. A minimum distance between the light extracting structure and the transparent carrying board is less than or equal to 125 μm.