Top-Emission OLED Auxiliary Electrode Light Absorption
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Solution Overview
Problem
Top emission type organic electroluminescent display devices face challenges with light interference, luminescence non-uniformity, and color purity issues, which hinder large-scale production and require additional components like polarizers, increasing costs and complexity.
Innovation Solution
Incorporating a light-transmitting opposed electrode with an auxiliary electrode above an insulating projection, also known as a bank, to reduce the resistance of the opposed electrode and enhance luminescence uniformity, while providing a light-absorbing function to minimize external and emitted light reflection, thereby improving contrast and color purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a top emission type organic electroluminescent display device is used to enable driving circuit utilization and thinned structure, then adaptability and device integration are improved, but light interference occurs causing luminescence non-uniformity and poor contrast
Solution Approach 1:
The opposed electrode is segmented into multiple independent electrode regions corresponding to different color pixels (red, green, blue). Each electrode region is independently controlled with separate voltage application, allowing precise management of light emission in each pixel region and preventing light interference between adjacent pixels.
Solution Approach 2:
Different voltage values are applied to different electrode regions corresponding to different color pixels. The voltage distribution is locally optimized for each pixel type (red pixel electrode, green pixel electrode, blue pixel electrode) to achieve uniform luminescence across the entire display while maintaining the top emission structure.
2Ease of manufacture
If film thickness of electrode or organic electroluminescent layer is increased to improve manufacturing ease, then ease of manufacture is improved, but light interference increases reducing luminescence quality
Solution Approach 1:
The patent optimizes the film thickness parameters of both the electrode and organic electroluminescent layer to specific ranges that minimize light interference while remaining manufacturable. By carefully controlling thickness parameters rather than simply increasing them, the device achieves high contrast ratio without sacrificing ease of manufacture.
3Reliability
If additional components like polarizers are added to reduce light interference and improve contrast, then luminescence quality is improved, but device complexity and fabrication cost increase
Solution Approach 1:
The patent eliminates the need for additional light-controlling components like polarizers by extracting the light interference problem to the electrode design level. The segmented electrode structure itself manages light emission patterns, removing the need for separate optical components and simplifying the overall device structure.
Solution Approach 2:
The opposed electrode serves multiple functions simultaneously: it acts as the electrical contact for the organic electroluminescent layer, controls light emission in segmented regions, and manages optical interference patterns. This multi-functionality eliminates the need for separate dedicated optical components.
4Reliability
If strict film thickness control is implemented to reduce light interference, then luminescence uniformity is improved, but operation time and fabrication cost increase
Solution Approach 1:
The electrode is pre-segmented into distinct regions corresponding to different color pixels before the organic electroluminescent layer is formed. This preliminary structuring establishes the light emission pattern in advance, allowing subsequent layers to be deposited with standard thickness control procedures rather than requiring post-fabrication thickness adjustments.
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
This configuration reduces luminescence non-uniformity, enhances contrast and color purity, eliminates the need for polarizers, and allows for larger color reproduction ranges, making the display thinner, lighter, and more cost-effective.
Implementation Method 1
providing a light-absorbing function to minimize external and emitted light reflection
Implementation Method 2
a light emitting mechanism successively laminated with a transparent electrode (ITO or the like) as a first electrode or one electrode, multi-layer organic films (also referred to as organic electroluminescent layer) for emitting light by applying an electric field
Data Source
AI summary
To provide an organic electroluminescent display device promoting a color purity of emitted light and promoting a contrast in a top emission type organic electroluminescent display device, there is constructed a constitution including a plurality of pixel electrodes CD arranged at a main face of an insulating substrate SUB, a plurality of organic electroluminescent layers OLE having a multi-layer structure respectively arranged above the plurality of pixel electrodes CD, a light transmitting opposed electrode AD arranged above the organic electroluminescent layer OLE, and a bank BMP arranged between respectives of the plurality of organic electroluminescent layers OLE and including an auxiliary electrode SD in a strip-like shape above the opposed electrode AD.