AMOLED Pixel Driving Circuit With Double-Gate TFT Leakage Control
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Solution Overview
Problem
Active matrix organic light-emitting diode (AMOLED) pixel driving circuits face instability and leakage current issues due to voltage drift and threshold voltage changes, affecting display reliability.
Innovation Solution
A pixel driving circuit with a double-gate thin film transistor and a conductive layer forming a capacitor, along with a second thin film transistor, is designed. The first thin film transistor includes a conductor portion with a higher doping concentration, and the second thin film transistor has a lower doping concentration, with a conductive layer connected to an initial voltage terminal and a gate connected to an enable signal terminal, stabilizing node voltages and reducing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional thin film transistor structure is used in AMOLED pixel driving circuits, then the device complexity is low, but leakage current increases and operation reliability deteriorates due to voltage drift and threshold voltage changes
Solution Approach 1:
The invention divides the thin film transistor into a double-gate structure with separate first gate and second gate, allowing independent control of threshold voltage and operation stability. The first gate controls the threshold voltage to prevent drift, while the second gate maintains operation stability, thereby resolving the contradiction between reliability and complexity by segmenting the control functions.
Solution Approach 2:
The invention applies different doping concentrations to different regions of the active layer: a first doping concentration in the channel region under the first gate for threshold voltage control, and a second doping concentration in the channel region under the second gate for stability. This local differentiation allows each gate to perform its specific function optimally, improving reliability without excessive complexity.
2Object-generated harmful factors
If the doping concentration in the active layer is increased to reduce leakage current, then leakage current decreases, but threshold voltage drift increases affecting display reliability
Solution Approach 1:
The invention segments the active layer into different doping regions: a first doped region with higher doping concentration under the first gate to suppress leakage current, and a second doped region with lower doping concentration under the second gate to maintain stable threshold voltage. This segmentation allows simultaneous reduction of leakage current and prevention of threshold voltage drift, resolving the contradiction between these two reliability aspects.
Solution Approach 2:
Different doping concentrations are applied locally to different regions of the active layer to achieve different functional objectives. The first doped region uses higher concentration for leakage suppression, while the second doped region uses lower concentration for threshold voltage stability, thereby eliminating the trade-off between leakage current and display reliability.
3Reliability
If a double-gate thin film transistor structure with differentiated doping regions is implemented, then threshold voltage stability and leakage current reduction are achieved, but the manufacturing process complexity increases
Solution Approach 1:
The invention forms the first doped region and second doped region in a predetermined sequence during the manufacturing process. The first doped region is created first, followed by the second doped region, allowing systematic control of the doping process. This preliminary planning of the doping sequence simplifies the manufacturing process despite the increased structural complexity, making the differentiated doping approach feasible for production.
4Reliability
If the conductive layer is positioned closer to the conductor portion to form a capacitor, then voltage stability improves, but the risk of short circuit increases
Solution Approach 1:
The invention introduces an insulating layer as an intermediary between the conductive layer and the conductor portion, forming a capacitor structure. This insulating layer prevents direct electrical contact and short circuits while maintaining the close proximity needed for effective voltage stabilization. The insulating layer acts as a mediator that enables the capacitor function without introducing short circuit risk, resolving the contradiction between voltage stability and short circuit prevention.
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 solution significantly reduces the risk of leakage current and enhances operation reliability by maintaining stable voltages and resisting threshold voltage drift, improving the overall performance of the AMOLED pixel driving circuit.
Implementation Method 1
The conductive layer and the conductor portion form a capacitor
Implementation Method 2
The conductor portion has a first doping concentration... A portion of the second active layer directly opposite to the first gate has a second doping concentration. The second doping concentration is lower than the first doping concentration.
Data Source
AI summary
A pixel driving circuit includes a first thin film transistor having a double-gate structure, a conductive layer and a second thin film transistor. The first thin film transistor includes a first active layer. The first active layer includes a first and second semiconductor portions and a conductor portion located therebetween. The conductor portion has a first doping concentration. The conductive layer is at least partially opposite to the conductor portion, so that the conductive layer and the conductor portion form a capacitor. The conductive layer is configured to electrically connect to an initial voltage terminal. The second thin film transistor includes a second active layer and a first gate. A portion of the second active layer directly opposite to the first gate has a second doping concentration, and the second doping concentration is lower than the first doping concentration.