OLED Display Transistors with Mixed Crystallinity for Cross-Talk Reduction
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Solution Overview
Problem
Existing OLED displays face issues with cross-talk and reduced light emission due to high off current in switching transistors and low mobility and stability in driving transistors, leading to decreased OLED lifetime and image sticking.
Innovation Solution
The OLED display incorporates thin film transistors with semiconductor layers of different crystallinity, where switching transistors are formed using amorphous semiconductor materials to minimize off current and driving transistors are formed using microcrystalline or polycrystalline semiconductor materials to enhance carrier mobility and stability, thereby improving current flow and luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If switching transistor uses conventional semiconductor material, then off current is reduced, but cross-talk occurs due to insufficient current blocking
Solution Approach 1:
The patent applies different semiconductor material properties to different transistor types within the same display device. Switching transistors use amorphous semiconductor material optimized for low off-current, while driving transistors use microcrystalline or polycrystalline semiconductor material optimized for high mobility. This local differentiation resolves the contradiction by allowing each transistor type to have optimized properties for its specific function.
2Speed
If driving transistor uses conventional semiconductor material, then mobility is improved, but stability decreases leading to image sticking
Solution Approach 1:
The patent differentiates semiconductor material properties between switching and driving transistors. Driving transistors use microcrystalline or polycrystalline semiconductor materials that provide both high carrier mobility for fast response and improved stability to prevent image sticking, while switching transistors use amorphous materials for low off-current. This resolves the contradiction between speed and stability.
3Ease of manufacture
If uniform semiconductor material is used for all transistors, then manufacturing is simplified, but performance optimization is limited
Solution Approach 1:
The patent changes the semiconductor material parameter (crystallinity) to optimize transistor performance. By using amorphous semiconductor for switching transistors and microcrystalline/polycrystalline semiconductor for driving transistors, the patent achieves superior display performance while maintaining relatively simple manufacturing processes through sequential deposition techniques.
Data Source
AI summary
In one embodiment, an organic light emitting diode (OLED) display is provided. The OLED display includes a substrate, a first signal line formed on the substrate, a second signal line intersecting the first signal line, a first thin film transistor connected to the first and second signal lines, a second thin film transistor connected to the first thin film transistor, a first electrode connected to the second thin film transistor, a second electrode provided at least partially opposite to the first electrode, and a light emitting member formed between the first electrode and the second electrode, wherein at least one of the first thin film transistor and the second thin film transistor includes a plurality of semiconductor layers having different crystallinity.