OLED Cathode Voltage Uniformity via Conductive Filler
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Solution Overview
Problem
Large-area OLED displays face challenges in maintaining 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 luminance deviations, and existing solutions complicate manufacturing and increase costs.
Innovation Solution
The implementation of a conductive filler layer between substrates, with a power line electrically connected to the cathode, allows for uniform low potential power voltage distribution, reducing voltage variations and simplifying the manufacturing process by eliminating the need for additional connection areas and barrier formations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a transparent conductive material or thin opaque conductive material is used for the cathode in top emission type displays, then the transmittance of the cathode is improved, but the surface resistance increases causing luminance variation
Solution Approach 1:
The patent introduces a low resistance conductive layer as an intermediary component between the cathode and the organic light emitting diode. This mediator layer compensates for the high surface resistance of the thin cathode material, providing an additional low-resistance path for current flow and thereby reducing luminance variation across the display surface.
Solution Approach 2:
The patent employs a composite structure combining the thin cathode material (for transmittance) with a low resistance conductive layer (for electrical conductivity). This composite approach allows the system to simultaneously achieve both high transmittance and low effective resistance, resolving the contradiction between these two requirements.
2Reliability
If a low potential power voltage line is formed on the lower substrate to prevent voltage drop, then the luminance uniformity is improved, but the device complexity and manufacturing complexity increase
Solution Approach 1:
The patent merges the low resistance conductive layer with existing structural elements (either the cathode itself or the encapsulation layer) rather than creating a separate dedicated power voltage line. This integration approach provides the necessary electrical compensation while avoiding additional connection structures and manufacturing steps.
Solution Approach 2:
The low resistance conductive layer serves multiple functions: it acts as part of the cathode structure, provides electrical compensation for voltage drop, and can simultaneously serve as an encapsulation or protective layer. This multi-functionality eliminates the need for separate dedicated components, reducing overall device complexity.
3Reliability
If a low potential power voltage line is formed on the lower substrate, then the luminance uniformity is improved, but the manufacturing cost and time increase while yield decreases
Solution Approach 1:
The low resistance conductive layer is formed as part of the preliminary cathode fabrication process, integrating the voltage compensation function into the existing manufacturing flow. This preliminary integration avoids the need for additional post-processing steps, barrier formations, or complex connection procedures, thereby maintaining manufacturing simplicity and yield.
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 solution achieves uniform luminance across the OLED display, reduces manufacturing complexity and costs, and enhances the applicability to high-resolution displays with small-sized pixels by minimizing voltage deviations and improving yield.
Implementation Method 1
a conductive filler layer interposed between the first substrate and the second substrate... a power line electrically connected to a portion of the exposed cathode through the conductive filler layer
Data Source
AI summary
An organic light emitting diode display is disclosed. The organic light emitting diode display includes a first substrate and a second substrate facing each other, and a conductive filler layer between the first and second substrates. The first substrate includes a bank layer having an opening exposing at least a portion of an anode, a spacer on the bank layer, an organic compound layer and a cathode disposed on the anode, the bank layer, and the spacer, an inorganic layer disposed on the cathode and including a first open hole exposing at least a portion of the cathode on the spacer, and an organic layer disposed on the inorganic layer and including a second open hole exposing at least a portion of the cathode on the spacer. The second substrate includes a power line electrically connected to a portion of the exposed cathode through the conductive filler layer.