Oxide-Polysilicon Pixel Circuit for OLED Leakage Reduction
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Solution Overview
Problem
Low-temperature polysilicon (LTPS) thin film transistors in OLED display devices exhibit large leakage currents, leading to unstable current in OLED light-emitting elements and flicker phenomena due to unstable voltage differences between gate and source electrodes.
Innovation Solution
A display panel design incorporating polysilicon and oxide transistors, including a driving transistor, data writing transistor, storage capacitor, and restoring transistors, with a specific layer structure and connection configuration to reduce leakage current and stabilize the current in OLED light-emitting elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If LTPS thin film transistor is used in pixel circuit, then high mobility and strong driving capability are achieved, but leakage current becomes large causing voltage instability and flicker
Solution Approach 1:
The patent applies different semiconductor material properties to different transistor functions within the pixel circuit. Specifically, LTPS transistors are used for high-speed switching operations where mobility is critical, while oxide semiconductors are used for transistors requiring low leakage current to maintain voltage stability. This local differentiation of material quality allows the circuit to simultaneously achieve both high speed and low leakage current by matching material properties to functional requirements.
2Power
If LTPS thin film transistor is used, then driving capability is improved, but leakage current increases causing current instability in OLED
Solution Approach 1:
The patent implements local quality differentiation by assigning LTPS transistors to roles requiring high driving capability while using oxide semiconductor transistors in positions where low leakage current is paramount for maintaining stable OLED operation. This spatial differentiation of material properties enables the circuit to achieve both strong driving capability and stable current output simultaneously.
3Reliability
If oxide transistor is used for restoring function, then leakage current is reduced and voltage stability is improved, but device complexity increases
Solution Approach 1:
The patent applies oxide semiconductor material specifically to the restoring transistor where low leakage current is most critical for maintaining voltage stability during the holding phase. By localizing the use of oxide transistors to this specific function rather than throughout the entire circuit, the design achieves voltage stability improvement while minimizing the increase in overall device complexity.
Data Source
AI summary
An embodiment of the present application discloses a display panel. A pixel circuit includes a driving transistor, a data writing transistor, a storage capacitor, and a first restoring transistor. A gate electrode of the first restoring transistor is electrically connected to a second scanning line, a source electrode of the first restoring transistor is electrically connected to a first node, and a drain electrode of the first restoring transistor is electrically connected to a first restoring signal source, wherein the first restoring transistor is an oxide transistor, and the driving transistor and the data writing transistor are polysilicon transistors.