Pixel Circuit with Shared Gate Electrode for Display Uniformity
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Solution Overview
Problem
Existing display technologies face challenges in achieving uniformity and quality of images, particularly at low frequencies and low brightness, due to issues like threshold voltage shifts in driving transistors and increased leakage currents.
Innovation Solution
The proposed pixel circuit incorporates a driving sub-circuit, writing sub-circuit, compensation sub-circuit, and reset sub-circuit, along with a specific layout and timing control, to provide a driving current to the light-emitting element while compensating for threshold voltage drifts and reducing leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pixel circuits are used, then the display can operate, but threshold voltage shifts cause image non-uniformity and increased leakage currents at low frequencies and low brightness
Solution Approach 1:
The pixel circuit is divided into multiple functional modules: driving sub-circuit, writing sub-circuit, compensation sub-circuit, and reset sub-circuit. Each module performs a specific function to address different aspects of the problem, with the compensation sub-circuit specifically targeting threshold voltage drift and leakage current issues
Solution Approach 2:
The compensation sub-circuit performs preliminary compensation for threshold voltage drift before the light-emitting phase. By pre-adjusting the driving transistor parameters and compensating for expected drift, the circuit maintains image uniformity throughout the display period, particularly during low frequency and low brightness operation
2Reliability
If double-gate design is used to improve performance, then threshold voltage control improves, but pixel area increases and resolution decreases
Solution Approach 1:
The gate electrode and storage capacitor electrode are merged into a single conductive structure. The first conductive layer serves dual functions: as the gate electrode for the driving transistor and as one electrode of the storage capacitor. This integration eliminates the need for separate double-gate structures while maintaining effective threshold voltage control
Solution Approach 2:
The first conductive layer performs multiple functions simultaneously: it acts as the gate electrode for the driving transistor, serves as an electrode for the storage capacitor, and provides threshold voltage control. This multi-functionality achieves the performance benefits of double-gate design without the additional area cost
3Productivity
If pixel circuit area is reduced to improve resolution, then more pixels fit in the display, but circuit functionality and compensation capabilities are compromised
Solution Approach 1:
Multiple circuit elements are merged into shared structures: the gate electrode and storage capacitor electrode are combined in the first conductive layer, and the driving transistor and third transistor share a common active layer structure. These mergers reduce the total pixel area while preserving all necessary circuit functions
Solution Approach 2:
The circuit layout utilizes vertical stacking and overlapping areas in the third dimension (z-axis). The first conductive layer overlaps with the first active layer to form both the gate electrode and storage capacitor, effectively using spatial overlap to reduce planar area consumption while maintaining functional integrity
Data Source
AI summary
A pixel circuit includes a first transistor, a third transistor, and a storage capacitor, the pixel circuit further including a base substrate and a first semiconductor layer and a first conductive layer stacked on the base substrate. The first semiconductor layer includes a first active layer of the first transistor and a third active layer of the third transistor. The first conductive layer includes a first electrode plate and a first gate block of the storage capacitor, an overlapping area of the first gate block and the first active layer of the first transistor serves as a gate electrode of the first transistor, the first electrode plate serves as a gate electrode of the third transistor, and an overlapping area of the third active layer of the third transistor and the first electrode plate serves as a channel region of the third transistor.