OLED Cathode Segmentation for Luminance Uniformity
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Solution Overview
Problem
Large-area OLED displays face issues with uniform luminance due to variations in power voltage across the active area, particularly in top emission type displays where the cathode's surface resistance leads to significant luminance variations depending on position.
Innovation Solution
The implementation of an auxiliary electrode connected to the cathode, with a barrier and cover layer configuration that ensures continuity and minimizes voltage variations, using materials like aluminum oxide or silicon nitride for the cover layer, and a protective layer to prevent moisture penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the cathode is formed of transparent conductive material (ITO) or thin opaque conductive material to secure transmittance in top emission type display, then light transmittance is improved, but surface resistance increases causing luminance variation depending on position
Solution Approach 1:
The cathode is divided into multiple segments along the power supply direction, with each segment independently connected to the power line. This segmentation allows each cathode segment to receive power directly, reducing the cumulative resistance effect and minimizing luminance variation across the display surface.
Solution Approach 2:
The invention transitions from a single-layer cathode structure to a multi-layer structure including cathode, protective layer, and cover layer. This dimensional addition allows the cathode to maintain thinness for transmittance while the additional layers provide electrical compensation and environmental protection, resolving the contradiction between transmittance and luminance uniformity.
2Illumination intensity
If the cathode thickness is reduced to maintain transmittance in top emission type display, then light transmittance is improved, but voltage stability deteriorates due to increased surface resistance
Solution Approach 1:
The invention uses a composite structure combining cathode material with protective and cover layers. The cathode layer maintains minimal thickness for transmittance, while the composite structure as a whole provides enhanced electrical stability and environmental protection, allowing thin cathode design without sacrificing voltage stability.
3Area of stationary object
If the cathode covers most of the active area to improve coverage, then area coverage is improved, but power voltage uniformity deteriorates due to resistance across the large area
Solution Approach 1:
The large-area cathode is segmented into multiple regions with independent power connections. Each segment is directly connected to the power line, eliminating the voltage drop that would occur across long cathode traces. This allows full area coverage while maintaining voltage uniformity across the entire active area.
4Illumination intensity
If transparent conductive material is used for cathode to enable top emission, then light transmittance is improved, but manufacturing complexity increases due to material selection and process control
Solution Approach 1:
The invention uses the same transparent conductive material (ITO) for both the cathode and auxiliary electrode, maintaining material homogeneity throughout the structure. This simplifies manufacturing by using consistent materials and processes, while the multi-layer structure provides the necessary functional differentiation without increasing material complexity.
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 achieves uniform luminance across the OLED display by reducing voltage variations and enhancing product reliability through improved manufacturing processes and moisture protection.
Implementation Method 1
The OLED includes an anode, a cathode, and an organic compound layer between the anode and the cathode. The OLED display is configured such that the OLED emits light while excitons formed by combining holes from the anode and electrons from the cathode inside an emission layer fall from an excited state to a ground state
Data Source
AI summary
An organic light emitting diode display is discussed. The organic light emitting diode display can include a substrate including a thin film transistor region in which a thin film transistor and an organic light emitting diode connected to the thin film transistor are disposed, and an auxiliary electrode region in which an auxiliary electrode is disposed, a barrier disposed on the auxiliary electrode, a cathode included in the organic light emitting diode, divided by the barrier, and exposing at least a portion of the auxiliary electrode, an end of the cathode being in direct contact with the auxiliary electrode, and a cover layer disposed on the cathode, the cover layer having continuity to cover the barrier and the auxiliary electrode.