OLED Sub-Pixel Planarization for Uniform RGB Emission Thickness
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Solution Overview
Problem
Organic light-emitting display (OLED) devices face deterioration in light-emitting characteristics due to surface level differences under the organic light-emitting layer, affecting the thickness and reproducibility of red, green, and blue light emissions.
Innovation Solution
The OLED device design includes sub-pixels with varying surface level differences for red, green, and blue light-emitting layers, with specific surface level differences of 30 nm or less for red, 40 nm or less for green, and 100 nm or less for blue, and a planarization layer to maintain uniform thickness and prevent deterioration, allowing for different shapes and sizes of sub-pixels without a special planarization process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the organic light-emitting layer is formed with different thicknesses for each color to improve color reproducibility, then the resonance distance is adjusted, but surface level differences cause thickness variations that deteriorate light-emitting characteristics
Solution Approach 1:
The patent applies local quality by setting different surface level difference thresholds for different color sub-pixels (30 nm for red, 40 nm for green, 100 nm for blue) based on their specific optical characteristics and thickness requirements, rather than using a uniform threshold for all colors
Solution Approach 2:
The patent performs preliminary action by controlling the surface level difference of the planarization layer before forming the organic light-emitting layer, ensuring that the underlying surface meets the required flatness specifications prior to organic material deposition, which prevents thickness variations in the final layer
2Manufacturing precision
If a planarization layer is added to maintain uniform thickness, then surface level differences are controlled, but the device structure and manufacturing complexity increase
Solution Approach 1:
The planarization layer serves multiple functions: it planarizes the underlying surface to control surface level differences, provides a stable base for organic layer formation, and can be integrated with existing pixel defining layer structures, reducing the need for additional separate planarization processes
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 approach effectively prevents deterioration of light-emitting characteristics by maintaining uniform thickness and reproducibility of each color sub-pixel, enhancing the overall performance and longevity of the OLED device.
Implementation Method 1
Holes and electrons are injected into the organic light-emitting layer through the anode electrode and the cathode electrode, and are recombined in the organic light-emitting layer to generate excitons (electron-hole pairs). The excitons emit energy which is discharged when an excited state returns to a ground state. As a result, the organic light-emitting layer (or, the organic light-emitting element) emits light.
Data Source
AI summary
A light-emitting display device includes unit pixels each of which includes a first sub-pixel, a second sub-pixel, and a third sub-pixel. The first sub-pixel includes a red organic light-emitting layer to emit red light. The second sub-pixel includes a green organic light-emitting layer to emit green light. The third sub-pixel includes a blue organic light-emitting layer to emit blue light. A surface level difference of the second sub-pixel is greater than a surface level difference of the first sub-pixel and smaller than a surface level difference of the third sub-pixel.