OLED Display Semi-Transmissive Layer Refractive Index Engineering
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Solution Overview
Problem
Large-sized organic light emitting diode (OLED) displays face challenges in achieving high luminous efficiency and color reproduction due to the limitations of the top emission type, which often convert to bottom emission type for practicality, resulting in lower performance and increased manufacturing complexity.
Innovation Solution
The implementation of a semi-transmissive layer with multiple refractive sub-layers having different refractive indices, positioned between the substrate and the first electrode, which refracts light at different angles to enhance luminous efficiency and color reproduction, allowing for a bottom emission type OLED display without the need for varying organic emission layer thicknesses by wavelength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a top emission type OLED display is used, then luminous efficiency and color reproduction are improved, but it becomes difficult to realize large-sized displays due to increased sheet resistance of the second electrode
Solution Approach 1:
The patent inverts the conventional top emission structure by implementing a bottom emission type OLED display. The second electrode is positioned at the bottom and configured to be substantially light reflective rather than semi-transmissive, while the first electrode at the top is configured to substantially transmit visible light. This inversion allows for large-sized displays while maintaining luminous efficiency through the reflective second electrode that redirects light upward through the transparent first electrode.
2Area of stationary object
If the OLED display is made bottom emission type to achieve large size, then manufacturing becomes easier, but luminous efficiency and color reproduction deteriorate
Solution Approach 1:
The patent applies parameter changes by introducing a semi-transmissive layer with multiple refractive sub-layers having different refractive indices between the substrate and the first electrode. This layer refracts light at different angles to enhance luminous efficiency and color reproduction in the bottom emission type display, thereby improving performance without sacrificing the large-size advantage.
3Loss of energy
If different thicknesses for each organic emission layer are used to improve color reproduction, then manufacturing complexity and time increase due to additional mask processes
Solution Approach 1:
The patent changes the optical parameters by introducing refractive sub-layers with different refractive indices instead of varying the thickness of organic emission layers. This approach achieves improved color reproduction and luminous efficiency through refractive index variation rather than thickness variation, eliminating the need for additional mask processes and reducing manufacturing 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
This configuration improves luminous efficiency and color reproduction in OLED displays, enabling their use in large-sized devices while simplifying the manufacturing process by maintaining consistent organic emission layer thicknesses across different wavelengths.
Implementation Method 1
a semi-transmissive layer positioned between the substrate and the first electrode, where the semi-transmissive layer includes a plurality of refractive sub-layers, which are configured not to carry an electrical signal or current, where two abutting ones of the plurality of sub-layers have different refractive indices
Data Source
AI summary
An organic light emitting diode display is disclosed. The display includes: a substrate; a first electrode positioned on the substrate; an organic emission layer positioned on the first electrode; a second electrode positioned on the organic emission layer; and a semi-transmissive layer positioned between the substrate and the first electrode and having a plurality of refractive layers having different refractive indices.