OLED Pixel Capacitor Layout for Higher Aperture Ratio
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Solution Overview
Problem
The challenge in organic light emitting display devices is to enhance the aperture ratio to improve display performance and extend the lifespan of light emitting diodes while simplifying the structure.
Innovation Solution
The solution involves a pixel structure with a driving thin film transistor positioned above the light emission area and a storage capacitor integrated within the light emission area, featuring a first capacitor formed horizontally between the gate and source electrodes of the driving thin film transistor and a second capacitor formed vertically between the gate electrode of the driving thin film transistor and the light emitting diode's first electrode, which increases the aperture ratio and simplifies the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a storage capacitor is provided per pixel to maintain current during light emission, then the display device can maintain stable light output, but the aperture ratio is reduced due to the capacitor occupying additional area
Solution Approach 1:
The patent combines the storage capacitor with the light emitting diode structure by forming the capacitor within the same pixel area as the LED. The capacitor is integrated into the pixel structure such that it shares space with other pixel components, specifically utilizing the area between the gate electrode and source/drain electrodes of the driving transistor, thereby eliminating the need for separate dedicated capacitor area and improving aperture ratio while maintaining current stability
Solution Approach 2:
The patent utilizes vertical stacking and three-dimensional spatial arrangement to accommodate the capacitor within the pixel plane. By forming the capacitor in a vertical direction between different conductive layers (gate electrode and source/drain electrodes), the design efficiently uses the Z-dimension to pack more functionality into the same two-dimensional pixel area, thus improving aperture ratio without compromising capacitor functionality
2Duration of action of stationary object
If the aperture ratio is increased to improve display performance and extend LED lifespan, then current density decreases and LED lifespan increases, but the storage capacitor area is reduced
Solution Approach 1:
The storage capacitor is merged with the driving transistor structure by utilizing the area between the gate electrode and source/drain electrodes. This integration allows the capacitor to be formed within the existing transistor footprint rather than requiring additional dedicated space, enabling increased aperture ratio while maintaining sufficient capacitor area for stable current maintenance and extended LED lifespan
3Reliability
If a separate storage capacitor is added to each pixel to maintain current, then current stability is improved, but the pixel structure becomes more complex
Solution Approach 1:
The storage capacitor is merged with the driving transistor by forming it within the same pixel structure using the area between the gate electrode and source/drain electrodes. This integration eliminates the need for separate capacitor components and reduces the number of discrete elements in the pixel, thereby simplifying the overall pixel structure while maintaining current stability
Solution Approach 2:
The pixel structure is designed with multi-functionality where the same structural elements serve multiple purposes. The gate electrode and source/drain electrodes of the driving transistor not only control current flow through the LED but also form the electrodes of the storage capacitor. This multi-functional design reduces component count and simplifies structure while ensuring reliable current maintenance
Data Source
AI summary
A pixel comprises a pixel circuit connected to gate and data lines, and a light emitting diode having a first electrode connected to the pixel circuit, wherein the pixel circuit may include a driving thin film transistor connected to the first electrode of the light emitting diode, a first capacitor formed in a horizontal direction between a gate electrode and a source electrode of the driving thin film transistor, and a second capacitor formed in a vertical direction between the gate electrode of the driving thin film transistor and the first electrode of the light emitting diode.