Dual-Gate Pixel Circuit for OLED Threshold Voltage Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The stability of Driving Thin Film Transistors (DTFTs) manufactured using the Low Temperature Poly-silicon (LTPS) process is not maintained under various conditions, such as Excimer Laser Annealing (ELA) crystallization, long-term pressure, and temperature changes, which affects the current-driven method for Organic Light Emitting Diodes (OLEDs), making it challenging to achieve high Pixels Per Inch (PPI) displays.
Innovation Solution
A pixel circuit with a 2T1C structure comprising a storage capacitor, a first transistor, a second transistor, and a light emitting element, where the second transistor is a double-gate thin film transistor, and both transistors are either polycrystalline or zinc oxide thin film transistors, used to compensate for threshold voltage shifts, allowing for stable current output and high PPI displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex pixel circuits such as 7T1C are used to compensate for DTFT threshold voltage shifts, then the stability and display effect are improved, but the device complexity increases and manufacturing precision requirements increase
Solution Approach 1:
The patent changes the electrical parameters of the transistor by introducing a dual-gate structure where the second gate can independently control the threshold voltage. This allows dynamic adjustment of the transistor's electrical characteristics to compensate for threshold shifts without requiring complex circuit topologies like 7T1C, thereby maintaining reliability while reducing device complexity.
Solution Approach 2:
The second gate of the dual-gate transistor acts as an intermediary control element that mediates between the control signal terminal and the channel. By applying compensation signals to this intermediate gate, the patent can adjust the threshold voltage to counteract shifts caused by ELA crystallization, pressure, and temperature changes, achieving stable current output without complex circuitry.
2Manufacturing precision
If the PPI of the display panel is increased, then the display quality is improved, but the manufacturing precision requirements increase making complex pixel circuits unusable
Solution Approach 1:
The patent utilizes the second gate of the dual-gate transistor to dynamically adjust electrical parameters (threshold voltage) to compensate for process variations. This allows the use of simpler pixel circuit structures that can be manufactured with high precision at high PPI, as the electrical compensation is achieved through parameter control rather than complex circuit topologies.
3Power
If ELA crystallization is applied to improve transistor performance, then the mobility is improved, but the threshold voltage shifts occur affecting current stability
Solution Approach 1:
The second gate serves as an intermediary that can apply compensation signals to counteract threshold voltage shifts caused by ELA crystallization. While the first gate controls the main current flow and mobility, the second gate independently adjusts the threshold voltage to maintain stability, thus resolving the trade-off between improved mobility and threshold instability.
Solution Approach 2:
The dual-gate transistor structure enables a feedback mechanism where the second gate can sense and compensate for threshold voltage shifts caused by ELA processing. By applying appropriate compensation signals to the second gate, the system maintains stable threshold voltage despite the mobility improvements from crystallization, ensuring reliable current output.
Data Source
AI summary
The embodiments of the present disclosure provide a pixel circuit and a method for driving the same, a display panel and a display apparatus. The pixel circuit includes: a storage capacitor having a first terminal coupled to receive a first control signal; a first transistor having a first electrode electrically coupled to a first voltage signal terminal, and a gate electrically coupled to a second terminal of the storage capacitor; and a second transistor having a first electrode electrically coupled to the second terminal of the storage capacitor, a second electrode electrically coupled to a second electrode of the first transistor, and a gate coupled to receive a second control signal. A threshold voltage of the first transistor is compensated through the first control signal, the second control signal and a voltage signal applied at the first voltage signal terminal.