Transparent OLED Cathode Segmentation for Luminance Uniformity
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Solution Overview
Problem
Transparent organic light emitting display devices face challenges in maintaining uniform luminance and transparency due to voltage drops caused by the high electrical resistance of thin cathodes, which is exacerbated by the need for auxiliary electrodes that occupy valuable space, compromising the size of emissive and transmissive areas.
Innovation Solution
The introduction of an auxiliary electrode positioned between sub-pixel areas allows for shared electrical connectivity, reducing voltage drops without increasing cathode thickness, and optimizing pixel layouts to maintain transparency and luminance by mirroring emissive and transmissive areas relative to the auxiliary electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the cathode is made thin to maintain transparency, then light transmittance is improved, but electrical resistance increases causing non-uniform luminance
Solution Approach 1:
The cathode is divided into multiple segments: a first cathode region directly contacting the organic emission layer, and a second cathode region positioned closer to the transparent substrate. This segmentation allows the first region to maintain thinness for transparency while the second region provides additional electrical connectivity to reduce voltage drops and improve luminance uniformity.
Solution Approach 2:
The cathode structure extends in the vertical dimension with the first cathode region at one height and the second cathode region at another height closer to the substrate. This dimensional arrangement allows both transparency (through the thin first region) and electrical stability (through the extended second region) to be achieved simultaneously.
2Reliability
If auxiliary electrodes are added to reduce voltage drops, then luminance uniformity is improved, but the aperture ratio and transmissive area are reduced
Solution Approach 1:
The second cathode region serves multiple functions: it maintains electrical connectivity to reduce voltage drops (improving luminance uniformity) while simultaneously acting as part of the cathode structure itself rather than a separate auxiliary electrode. This multi-functionality eliminates the need for additional auxiliary electrodes that would reduce the aperture ratio.
Solution Approach 2:
The auxiliary electrode function is merged with the cathode structure by forming the second cathode region as an extension of the cathode itself. This integration allows the auxiliary functionality to be achieved without adding separate components that would occupy valuable aperture space.
3Reliability
If the cathode thickness is increased to reduce electrical resistance, then luminance uniformity is improved, but transparency is compromised
Solution Approach 1:
The cathode is segmented into a thin first cathode region for transparency and an extended second cathode region for electrical stability. This segmentation allows each region to be optimized for its specific function without compromising the other.
Solution Approach 2:
Different regions of the cathode have different thicknesses and properties: the first cathode region is thin to maintain transparency, while the second cathode region is positioned to provide electrical stability. This local differentiation allows both transparency and luminance uniformity to be achieved in their respective areas.
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 effectively reduces non-uniformity in luminance and maintains high light transmittance rates, ensuring uniform performance and transparency across the display device without compromising the aperture ratio of sub-pixels.
Implementation Method 1
an organic light emitting element, which includes an anode, an organic emission layer, and a cathode
Data Source
Figure 1a~1b
Figure 2
Figure 3
AI summary
Provided are an organic light emitting display device and a method for manufacturing the same. The organic light emitting display device includes a plurality of pixels, each including a set of sub pixels. Each of the sub pixels has an emissive area for emitting light and a transmissive area for passing the external light. At least two sub pixels are symmetrically arranged on each side of an auxiliary electrode, and share the auxiliary electrode.