OLED Light Extraction via Refractive Index Layering
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Solution Overview
Problem
Organic light-emitting devices (OLEDs) face challenges with low light extraction efficiency, which affects their emission efficiency and power consumption, and existing solutions require complex and costly processes to optimize refractive index layers for different emission colors.
Innovation Solution
A light-emitting apparatus with a stacked-layer structure featuring layers with specific refractive index differences, where the ordinary refractive index of the first and third layers is lower than the second layer, and an optional fourth layer adjusts the optical path to enhance light extraction efficiency across various emission colors, allowing for shared manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a low refractive index layer is added to improve light extraction efficiency, then light extraction efficiency is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines multiple functional layers (hole injection layer, hole transport layer, electron transport layer, and low refractive index layer) into an integrated stacked structure where layers with different refractive indices work together. This merging approach achieves improved light extraction efficiency while maintaining manageable device complexity through systematic integration of functions.
Solution Approach 2:
The patent employs composite layer structures combining materials with different refractive indices (e.g., organic compounds with refractive indices ranging from 1.3 to 2.0) to create an optimized optical pathway. This composite approach allows simultaneous achievement of electrical functionality and optical optimization without excessive complexity.
2Manufacturing precision
If separate optimization processes are used for different emission colors, then emission performance is improved, but manufacturing cost and process complexity increase
Solution Approach 1:
The patent designs a universal stacked-layer structure that can be applied across multiple emission colors (red, green, blue) by adjusting material composition and thickness parameters. This universal framework eliminates the need for completely separate optimization processes for each color, reducing manufacturing complexity while maintaining emission performance through parameter tuning within the same structural paradigm.
Solution Approach 2:
The patent optimizes emission characteristics by adjusting physical parameters such as layer thickness, refractive index values, and material composition within the stacked structure, rather than changing the fundamental layer architecture for each color. This parameter-based optimization approach maintains manufacturing simplicity while achieving color-specific performance optimization.
3Productivity
If multiple layers with specific refractive indices are stacked, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
The patent segments the light-emitting device into distinct functional layers (hole injection, hole transport, light-emitting, electron transport, electron injection) with progressively optimized refractive indices. This segmentation allows systematic improvement of light extraction efficiency through controlled addition of layers, balancing productivity enhancement with manageable device complexity through clear functional separation.
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 significantly improves light extraction efficiency and emission performance while simplifying the manufacturing process by using a common stacked-layer structure for multiple emission colors, reducing power consumption and increasing the lifespan of the devices.
Implementation Method 1
The ordinary refractive index of each of the first layer A and the third layer A is lower than the ordinary refractive index of the second layer A at the emission peak wavelength of the light-emitting substance A
Implementation Method 2
Low light extraction efficiency is often a problem in an organic EL device. In order to improve the light extraction efficiency, a structure including a layer formed using a low refractive index material in an EL layer has been proposed
Data Source
AI summary
A light-emitting apparatus with high emission efficiency is provided. The light-emitting apparatus includes light-emitting devices A and B each including an anode, a cathode, and an EL layer. An EL layer A includes a first layer A to a third layer A and a light-emitting layer A. An EL layer B includes a first layer B to a fourth layer B and a light-emitting layer B. The light-emitting layer A includes a light-emitting substance A and the light-emitting layer B includes a light-emitting substance B. An emission peak wavelength (wavelength A) of the light-emitting substance A is shorter than an emission peak wavelength (wavelength B) of the light-emitting substance B. The first layers A and B have similar structures, the second layers A and B have similar structures, and the third layers A and B have similar structures. The ordinary refractive index (no) of each of the first layer A and the third layer A is lower than the no of the second layer A at the wavelength A. The no of each of the first layer B and the third layer B is lower than the no of the second layer B at the wavelength B. The fourth layer B is positioned between the anode B and the first layer B, between the first layer B and the second layer B, between the first layer B and the third layer B, or between the third layer B and the light-emitting layer B.