OLED Auxiliary Lines for Voltage Drop and Luminance Uniformity
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Solution Overview
Problem
Organic light emitting display (OLED) devices face issues with voltage drop and luminance non-uniformity due to the increased electric resistance of thin cathodes, which also lead to a lower aperture ratio and complex manufacturing processes.
Innovation Solution
The OLED device incorporates a first auxiliary line formed of the same material as the source and drain electrodes and a second auxiliary line formed of the same material as the anode, which cross each other with a planarization layer in between, effectively reducing voltage drop and enhancing luminance uniformity while simplifying the manufacturing process by eliminating the need for a separate mask process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a transparent electrode or semi-transmissive electrode is used as the cathode with small thickness to improve light transmittance, then light transmittance is improved, but electric resistance of the cathode increases causing voltage drop and luminance non-uniformity
Solution Approach 1:
The cathode region is divided into multiple segments: the main cathode electrode and multiple auxiliary cathode electrodes positioned at different locations. This segmentation allows each electrode to serve specific functions - the main cathode provides primary electron injection while auxiliary electrodes compensate for voltage drops in different regions, thereby maintaining low electric resistance without compromising light transmittance of the main cathode
Solution Approach 2:
Auxiliary cathode electrodes are introduced as intermediary elements between the voltage supply pad and the main cathode electrode. These auxiliary electrodes act as intermediate conductors that distribute voltage more uniformly across the cathode, reducing the voltage drop that would otherwise occur in the thin transparent cathode material
2Reliability
If a separate auxiliary electrode is formed to minimize voltage drop, then voltage drop is reduced, but the aperture ratio is lowered due to reduced light emitting area
Solution Approach 1:
The auxiliary cathode electrodes are strategically positioned in specific regions where voltage drop is most problematic, rather than uniformly distributing electrodes across the entire device. This localized approach ensures that auxiliary electrodes are placed only where needed to compensate for voltage drops, minimizing their impact on the overall light emitting area while effectively addressing the voltage drop issue in critical regions
Solution Approach 2:
Instead of forming a complete mesh or extensive auxiliary electrode network that would significantly reduce aperture ratio, the invention uses a partial approach with selectively positioned auxiliary electrodes. This partial action provides sufficient voltage compensation in critical areas without excessively reducing the light emitting area, achieving an optimal balance between voltage drop reduction and aperture ratio maintenance
3Manufacturing precision
If a separate mask process is used to form the second auxiliary electrode below the first auxiliary electrode, then uniform sheet resistance is maintained, but the manufacturing process becomes complicated and manufacturing time increases
Solution Approach 1:
The formation of multiple auxiliary cathode electrodes is merged into a single simultaneous deposition process rather than requiring separate mask processes for each electrode. By combining the formation steps, the invention achieves uniform sheet resistance across all auxiliary electrodes while significantly simplifying the manufacturing process and reducing overall manufacturing time
Data Source
AI summary
Provided is an organic light emitting display (OLED) device that includes, for example, a thin film transistor including an active layer, a gate electrode, a source electrode, and a drain electrode; a planarization layer on the thin film transistor; an anode on the planarization layer; an organic light emitting layer on the anode; a cathode on the organic light emitting layer; a first auxiliary line on the same layer and formed of the same material as the source electrode and the drain electrode; and a second auxiliary line on the same layer and formed of the same material as the anode, wherein the first auxiliary line and the second auxiliary line cross each other with the planarization layer interposed therebetween, and wherein the first auxiliary line is electrically connected with the cathode through the second auxiliary line.