OLED Cathode Auxiliary Electrode Voltage Distribution
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Solution Overview
Problem
Organic light-emitting display devices experience brightness nonuniformity due to variations in the low-level voltage applied to the cathode, which affects the drive current and resulting light emission across different pixels on the display panel.
Innovation Solution
Incorporating a low-level voltage line and an auxiliary electrode connected through insulating layers, with the cathode making contact with the side of the auxiliary electrode, ensuring consistent low-level voltage distribution across the pixels, thereby addressing brightness variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the cathode is implemented as a transparent electrode receiving low-level voltage through a pad on the edge of the display panel, then the device structure is simplified, but brightness nonuniformity occurs due to voltage drop across different pixel positions
Solution Approach 1:
The low-level voltage supply is segmented into multiple independent paths: one through the edge pad and additional ones through auxiliary electrodes positioned at different locations on the substrate. This segmentation allows each pixel region to receive low-level voltage from the nearest auxiliary electrode, reducing the voltage drop distance and ensuring uniform brightness across the display panel while maintaining the simplified transparent electrode cathode structure.
Solution Approach 2:
Auxiliary electrodes are introduced as intermediary elements between the edge pad and the pixels. These auxiliary electrodes receive low-level voltage from the pad and distribute it to nearby pixels, acting as intermediate distribution points that reduce the overall voltage drop across the display panel and eliminate brightness nonuniformity.
2Illumination intensity
If auxiliary electrodes are added to distribute low-level voltage, then brightness uniformity is improved, but device complexity increases
Solution Approach 1:
The auxiliary electrodes are merged with the existing transparent electrode cathode material and formation process. Since both the cathode and auxiliary electrodes use the same transparent conductive material and deposition process, no additional material layers or separate formation processes are required. The auxiliary electrodes are simply additional patterned regions formed during the same cathode fabrication step, thus improving brightness uniformity without significantly increasing device complexity.
Data Source
AI summary
An organic light-emitting display device can include a low-level voltage line; a passivation layer that lies over the low-level voltage line; a planarization layer that lies over the passivation layer; an anode and an auxiliary electrode that lie on the planarization layer and the passivation layer, the auxiliary electrode is electrically connected to the low-level voltage line; a bank layer that lies over the anode, the planarization layer and the passivation layer and defines a light-emitting area; an organic emissive layer over the light-emitting area; and a cathode disposed on the organic light-emitting layer, in which the cathode is connected to a side of a protruding portion where the auxiliary electrode protrudes from the planarization layer.