OLED Pixel Circuit Three-Electrode Storage Capacitor
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Solution Overview
Problem
Existing pixel circuits in high-resolution OLED displays face challenges with current leakage and flicker due to instability in gate voltage, particularly at low frequencies, and the smaller storage capacitors required for high pixel density compromise display uniformity and stability.
Innovation Solution
A display substrate with a pixel circuit design that includes a driving sub-circuit, data writing sub-circuit, threshold compensation sub-circuit, current-leakage prevention sub-circuit, and storage sub-circuit, featuring a storage capacitor with three electrode plates to enhance capacitance and stability, and the use of oxide semiconductor thin film transistors to reduce leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high pixel density is implemented to increase resolution, then display resolution is improved, but storage capacitor size is reduced leading to decreased display uniformity and stability
Solution Approach 1:
The patent transitions from a planar two-electrode capacitor structure to a three-dimensional stacked three-electrode capacitor structure. The first and third electrode plates are positioned on opposite sides of the second electrode plate in the vertical direction, creating a multi-layer capacitance structure that increases storage capacitance without expanding horizontal area, thus maintaining high pixel density while improving display uniformity and stability
Solution Approach 2:
The patent implements a nested capacitor structure where the second electrode plate is positioned between and overlaps with the first and third electrode plates. This nested arrangement allows the storage capacitor to utilize vertical space efficiently, increasing capacitance value within the constrained pixel area required for high-resolution displays
2Device complexity
If conventional transistor structures are used to simplify device structure, then device complexity is reduced, but current leakage increases particularly at low frequencies
Solution Approach 1:
The patent employs oxide semiconductor materials (such as IGZO - indium gallium zinc oxide) for the transistor active layers instead of conventional silicon-based materials. This material substitution provides inherently lower off-state current and reduced current leakage while maintaining the transistor structure, effectively addressing the harmful leakage effect without significantly increasing device complexity
Solution Approach 2:
The patent applies different material compositions to different regions of the transistor structure. The oxide semiconductor material is specifically used in the active layer and channel region where current control is critical, while other parts of the device can use conventional materials. This localized application of specialized materials optimizes current leakage prevention where most needed
3Reliability
If gate voltage stability is improved to reduce flicker, then display uniformity is improved, but current leakage increases
Solution Approach 1:
The patent uses oxide semiconductor materials for the transistor active layers to achieve both stable gate voltage control and reduced current leakage. The unique properties of oxide semiconductors provide high mobility when on-state while maintaining extremely low off-state current, enabling stable gate voltage without the harmful leakage effects that would otherwise occur
Data Source
AI summary
A display substrate and a display panel. The display substrate includes: a base substrate; and a plurality of sub-pixels on the base substrate, each of the plurality of sub-pixels includes a light-emitting element and a pixel circuit for driving the light-emitting element to emit light, the pixel circuit includes a driving sub-circuit, a data writing sub-circuit, a threshold compensation sub-circuit, a current-leakage prevention sub-circuit and a storage sub-circuit; the storage sub-circuit includes a storage capacitor, the storage capacitor includes a first electrode plate, a second electrode plate and a third electrode plate, the first electrode plate and the third electrode plate are electrically connected to each other and are in different layers with respect to the base substrate, and the second electrode plate at least partially overlaps the first electrode plate and the third electrode plate in a direction perpendicular to the base substrate.