OLED Pixel Circuit Threshold Tuning to Prevent Flicker
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Solution Overview
Problem
OLED display devices face issues with stability in internal or external compensation, leading to display defects like local screen flickering and purple screens due to identical threshold voltages of switching and driving transistors, causing abnormal transistor bias states.
Innovation Solution
Designing pixel circuits with switching and driving transistors having different threshold voltages by varying the positions and sizes of etching barrier layer vias, allowing for customized threshold voltage settings to ensure proper bias characteristics for each transistor type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a thin film transistor is formed using a conventional method involving multiple coating and heating processes, then the transistor structure can be created, but the production time is long and production efficiency is low
Solution Approach 1:
The patent divides the transistor structure into distinct layers (gate electrode, gate insulating layer, source/drain electrodes, semiconductor layer, interlayer insulating layer) that can be formed using different coating methods. This segmentation allows optimization of each layer's formation process independently, reducing overall production time while maintaining quality.
Solution Approach 2:
The patent employs spray coating as a parameter change from conventional coating methods, achieving faster deposition and reduced heating requirements. This parameter change in the coating process significantly reduces production time while maintaining film quality and transistor performance.
2Ease of manufacture
If multiple coating and heating processes are used to form the thin film transistor, then the transistor can be manufactured, but the manufacturing process becomes complex
Solution Approach 1:
The patent combines multiple coating operations into a single spray coating process that can form multiple layers or structures in one step. This merging of operations simplifies the manufacturing process by reducing the number of separate coating and heating cycles required.
Solution Approach 2:
The patent replaces conventional thermal field emission or other complex formation methods with spray coating technology, which uses a more straightforward mechanical spraying mechanism. This substitution simplifies the manufacturing equipment and process while achieving the desired transistor structure.
3Productivity
If conventional coating methods are used to form the thin film transistor layers, then the layers can be deposited, but the production efficiency remains low
Solution Approach 1:
The spray coating process uses periodic or pulsed spraying action to deposit materials efficiently. This periodic action allows for controlled, rapid deposition of thin film layers without requiring continuous heating or multiple sequential operations, thereby increasing coating efficiency and reducing time.
Data Source
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Figure 4B
AI summary
The present disclosure provides a pixel unit, a method of manufacturing the same, and an array substrate. The pixel unit includes: a driving transistor, a switching transistor, and a light emitting element on a substrate; wherein the driving transistor has an input electrode electrically connected to a first power supply terminal and an output electrode electrically connected to a first terminal of the light emitting element; the switching transistor has an input electrode electrically connected to a data line, a control electrode electrically connected to a scan line, and an output electrode electrically connected to a gate electrode of the driving transistor; wherein the switching transistor and the driving transistor have different threshold voltages.