Dual-Gate TFT AMOLED Display Prevents Threshold Voltage Shift
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Solution Overview
Problem
Active matrix organic electroluminescent devices face threshold voltage shifts due to electron trapping in the gate dielectric layer, which reduces injection current and impacts OLED luminance, while existing solutions compromise aperture ratio.
Innovation Solution
The implementation of a self-emitting display device with first and second driving thin film transistors and storage capacitors, where the gates are coupled to different voltages to alternately drive a light-emitting diode, preventing electron trapping and threshold voltage shifts without reducing the aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single driving thin film transistor is used in an AMOLED, then the device structure is simple, but threshold voltage shift occurs due to electron trapping in the gate dielectric layer, reducing injection current and impacting OLED luminance
Solution Approach 1:
The patent divides the single driving transistor function into two separate thin film transistors (first driving TFT and second driving TFT), each with its own gate electrode. This segmentation allows independent control of the two transistors through different gate voltages, enabling one transistor to compensate for threshold voltage shifts while the other maintains normal operation, thus resolving the contradiction between structural simplicity and threshold voltage stability.
Solution Approach 2:
The patent changes the electrical parameters by applying different voltages to the gate electrodes of the two driving transistors during the same frame. By adjusting gate voltage parameters dynamically, the system can compensate for threshold voltage shifts and maintain stable injection current to the OLED, thereby improving reliability without significantly increasing structural complexity.
2Reliability
If additional driving transistors and storage capacitors are added to prevent threshold voltage shift, then threshold voltage stability improves, but the aperture ratio is reduced
Solution Approach 1:
The patent merges the first and second driving transistors in a shared configuration where they collectively control the light-emitting diode. By combining their functions and optimizing their spatial arrangement, the patent achieves threshold voltage compensation while minimizing the total area occupied by the driving circuitry, thus preventing excessive reduction in aperture ratio.
Solution Approach 2:
The patent utilizes vertical stacking and multi-layer configuration to accommodate the additional driving transistors and storage capacitors. By transitioning from a planar layout to a three-dimensional arrangement, the patent reduces the horizontal footprint of the driving circuit, thereby preserving more area for the light-emitting region and maintaining a high aperture ratio.
Data Source
AI summary
A system for displaying images is disclosed. The system includes a self-emitting display device including an array substrate having a pixel region. A light-emitting diode is disposed on the array substrate of the pixel region. First and second driving thin film transistors are electrically connected to a light-emitting diode. The first driving thin film transistor includes a first gate and an active layer stacked on the array substrate of the pixel region and the second driving thin film transistor includes the active layer and a second gate thereon. The first gate is coupled to a first voltage and the second gate is coupled to a second voltage different from the first voltage during the same frame.