OLED Second Electrode Resistance Reduction via Auxiliary Line
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Solution Overview
Problem
Large-size OLED devices face significant brightness non-uniformity issues due to increased resistance in the second electrode, which is exacerbated by the need for auxiliary lines to reduce resistance, leading to complex fabrication processes and increased production costs.
Innovation Solution
An organic light emitting display device with a transparent electrode having low resistivity, featuring a substrate with a pixel region and a non-pixel region, a first electrode, an organic emitting layer, a bank covering the auxiliary conductive line, and a second electrode connected to the auxiliary line, where the auxiliary line has a thickness greater than the first electrode, and the bank has a hydrophobic property and a stair-shaped side surface to reduce resistance and prevent voltage drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the thickness of the second electrode is lowered to achieve light-transmissive property, then the light transmission is improved, but the resistance of the second electrode is increased causing voltage drop and brightness non-uniformity
Solution Approach 1:
An auxiliary electrode is introduced as an intermediary element between the first electrode and the second electrode. This auxiliary electrode serves as a mediator to reduce the overall resistance in the electrical path, allowing the second electrode to maintain lower thickness for light transmission while the auxiliary electrode compensates for the resistance increase through its larger surface area and lower resistivity
Solution Approach 2:
The invention changes the physical parameters of the auxiliary electrode, specifically using a material with lower resistivity and increasing the surface area through extended coverage. This parameter change enables the auxiliary electrode to provide sufficient current distribution without requiring the second electrode to be thick, thus maintaining both light transmission and brightness uniformity
2Reliability
If an auxiliary line is added to reduce the resistance of the second electrode, then the brightness non-uniformity is prevented, but the fabrication process becomes more complex and production cost increases
Solution Approach 1:
The auxiliary electrode is merged with the second electrode in terms of material composition and formation process. Both electrodes are formed simultaneously in the same vacuum deposition chamber using the same cathode material, eliminating the need for separate processing steps and reducing fabrication complexity despite the additional functional element
Solution Approach 2:
The auxiliary electrode serves multiple functions: it acts as an additional current supply path to reduce resistance, provides electrical connection through contact holes, and can serve as a reference electrode for measurement. This multi-functionality reduces the need for separate dedicated components, simplifying the overall device structure
Data Source
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Figure 3~4A
AI summary
An organic light emitting display device includes a substrate including a pixel region and a non-pixel region; a first electrode over the substrate in the pixel region; an organic emitting layer over the first electrode in the pixel region; a bank over the substrate in the non-pixel region; an auxiliary conductive line covered by the bank in the non-pixel region, a thickness of the auxiliary line larger than a thickness of the first electrode; and a second electrode on the organic emitting layer in the pixel region and on the bank in the non-pixel region, the second electrode electrically connected to the auxiliary conductive line.