OLED Pixel Storage Capacitor Kickback Voltage Reduction
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Solution Overview
Problem
Organic light emitting diode (OLED) displays face challenges with kickback voltage variations, particularly when displaying black and white alternately, leading to afterimages due to the kickback voltage increase, which affects image quality and display uniformity.
Innovation Solution
Incorporating an additional storage capacitor formed by an overlapping layer and a third node in the OLED pixel structure, which reduces the kickback voltage by buffering voltage changes and stabilizing the third transistor's operation, thereby improving display characteristics and preventing afterimages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an OLED display uses a conventional pixel structure without additional storage capacitor, then the device complexity is low, but kickback voltage variations occur leading to afterimages and poor display uniformity
Solution Approach 1:
The patent merges the storage capacitor function with the existing transistor structure by forming the capacitor using the third node of the third transistor and an overlapping layer. This integration approach adds the necessary capacitance function without requiring a completely separate capacitor structure, thus improving display uniformity while limiting the increase in device complexity.
Solution Approach 2:
The third transistor's third node serves dual purposes: it functions as part of the transistor circuitry and simultaneously serves as one electrode of the storage capacitor. This multi-functionality reduces the need for additional dedicated capacitor structures, addressing the contradiction between reliability improvement and device complexity.
2Illumination intensity
If an OLED display displays black and white alternately, then the display can show high contrast images, but kickback voltage increases causing afterimages
Solution Approach 1:
The storage capacitor formed by the third node and overlapping layer provides beforehand cushioning by storing charge and compensating for kickback voltage variations before they affect the display. This preemptive charge storage mechanism mitigates the afterimage effect caused by alternating black and white display, maintaining image quality stability while preserving display contrast capability.
3Ease of manufacture
If the third transistor is used without additional capacitance, then the manufacturing process is simpler, but voltage changes are not buffered leading to operation instability
Solution Approach 1:
The storage capacitor is merged with the third transistor structure, using the third node as a shared element. This integration allows voltage buffering capability to be added without requiring separate capacitor fabrication processes, maintaining manufacturing simplicity while improving voltage stability for reliable transistor operation.
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
The additional storage capacitor effectively reduces kickback voltage variations, enhancing display uniformity and preventing afterimages, thus improving the overall image quality and stability of OLED displays.
Implementation Method 1
an additional storage capacitor formed by an overlapping layer and a third node in the OLED pixel structure, which reduces the kickback voltage by buffering voltage changes
Data Source
AI summary
An organic light emitting diode display includes a first transistor disposed on a substrate and including a gate electrode, an input electrode, and an output electrode, a second transistor electrically connected to a scan line, a data line, and the input electrode of the first transistor, a third transistor including a gate electrode, a first electrode electrically connected to the output electrode of the first transistor, and a second electrode electrically connected to the gate electrode of the first transistor, and an overlapping layer that overlaps the gate electrode of the third transistor in a plan view. The overlapping layer is disposed between the substrate and a semiconductor layer of the third transistor.