Transparent Storage Capacitor for OLED Aperture Ratio
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Solution Overview
Problem
Existing organic light-emitting diode displays face challenges in securing a storage capacitor with sufficient capacity without decreasing the aperture ratio, and they require complex manufacturing processes involving multiple mask steps, which increase costs and defect rates.
Innovation Solution
The solution involves forming a storage capacitor in the emission area using a transparent storage capacitor electrode, with the second electrode superposed on the first electrode and both formed from transparent conductive material, and simplifying the manufacturing process by reducing the number of mask steps through the use of a photosensitive insulating material for the overcoat layer and passivation layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a storage capacitor is formed in the emission area using conventional opaque electrodes, then the capacitor capacity is sufficient, but the aperture ratio decreases
Solution Approach 1:
The patent applies the principle of color changes by transitioning from opaque electrode materials to transparent conductive materials (such as ITO, IZO, or ZnO) for the storage capacitor electrodes. This material substitution changes the optical property from opaque to transparent, allowing light transmission through the capacitor region while maintaining the electrical functionality and sufficient capacitance in the emission area.
2Manufacturing precision
If multiple mask steps are used in the manufacturing process, then the manufacturing precision is improved, but the device complexity and production cost increase
Solution Approach 1:
The patent merges multiple separate mask steps into a single integrated mask process. Specifically, the pixel electrode and storage capacitor electrode are formed simultaneously in one mask step using transparent conductive material, and the bank pattern and emission layer pattern are formed in another integrated mask step. This consolidation maintains the required pattern alignment precision while reducing the total number of mask steps from four or more to just two, thereby simplifying the manufacturing process.
Solution Approach 2:
The patent applies universality by designing the mask pattern to serve multiple functions simultaneously. The same mask pattern defines both the pixel electrode region and the storage capacitor electrode region, and another mask pattern defines both the bank structure and the emission layer positioning. This multi-functional mask approach eliminates the need for separate dedicated mask steps for each component, reducing process complexity while maintaining precision.
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 approach allows for a storage capacitor with sufficient capacity to be formed without reducing the aperture ratio, thereby enhancing the display's ability to sustain pixel data and simplifying the manufacturing process, reducing costs and improving production yield.
Implementation Method 1
The organic light-emitting diode emits light according to energy from excitons generated through a process in which holes and electrons injected into the anode and the cathode are recombined in the EML
Implementation Method 2
the overcoat layer may contain a photosensitive insulating material
Data Source
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AI summary
An organic light-emitting diode display includes a substrate (SUB) in which an emission area (AA) and a non-emission area (NA) are defined; a thin film transistor (DT) disposed in the non-emission area on the substrate; a passivation layer (IN2) disposed on the thin film transistor; a first storage capacitor electrode (SG1) and a second storage capacitor electrode (SG2) superposed thereon, having the passivation layer (IN2) interposed therebetween, in the emission area; an overcoat layer (OC) disposed on the second storage capacitor electrode; and an anode (ANO) disposed on the overcoat layer, coming into contact with one side of the second storage capacitor electrode through an overcoat layer contact hole penetrating the overcoat layer and, coming into contact with part of the thin film transistor through a passivation layer contact hole disposed in the overcoat layer contact hole and penetrating the passivation layer.