Multi-Channel Driving Transistors for OLED Line Mura
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Solution Overview
Problem
Non-uniform transistor characteristics due to excimer laser annealing in organic electroluminescence displays lead to line mura, reducing image quality and yield.
Innovation Solution
Forming at least two channels in driving transistors perpendicular to the laser scan direction during crystallization, ensuring equal sums of lengths and widths to maintain consistent current supply to OLEDs, thereby preventing line mura formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If excimer laser annealing is used to crystallize the semiconductor layer, then the transistor can be formed with appropriate mobility and threshold voltage, but non-uniformities in the crystallization process cause line mura that reduces image quality
Solution Approach 1:
The single channel of the driving transistor is divided into multiple channels (first channel and second channel) that are arranged in different directions. This segmentation allows the transistor to average out the non-uniformities caused by laser scan direction, preventing line mura while maintaining the benefits of laser annealing crystallization.
2Ease of manufacture
If the driving transistor uses a single channel aligned with the laser scan direction, then the manufacturing process is simple, but transistor characteristics vary along the scan direction causing line mura
Solution Approach 1:
The patent introduces asymmetry in the channel arrangement by creating channels that extend in different directions relative to the laser scan direction. This asymmetric multi-channel structure compensates for the directional non-uniformities introduced by the laser scanning process, achieving uniform transistor characteristics across the display.
3Manufacturing precision
If multiple channels are formed in different directions to prevent line mura, then image quality improves, but the transistor structure becomes more complex
Solution Approach 1:
The patent applies local quality by making each channel have specific directional characteristics tailored to compensate for local non-uniformities in the laser annealing process. Each channel's orientation and dimensions are optimized for its specific position and function in counteracting the line mura effect.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Improves image quality by eliminating line mura caused by transistor non-uniformities, ensuring consistent current supply and maintaining image clarity across the display.
Implementation Method 1
a laser annealing process comprising crystallizing amorphous silicon into polycrystalline silicon
Implementation Method 2
crystallizing amorphous silicon into polycrystalline silicon
Implementation Method 3
electrons from the electron transport layer and holes from the hole transport layer are recombined in the emitting layer to emit light
Data Source
AI summary
Embodiments of an organic electroluminescence display capable of preventing line mura generated due to manufacturing differences in driving transistors are disclosed. The manufacturing differences may be due to deviations of irradiated energy beam density generated from an excimer laser annealing process for crystallizing amorphous silicon into polycrystalline silicon. One embodiment of an organic electroluminescence display a plurality of pixel circuits arranged perpendicular to a laser scan direction for crystallization. Each pixel circuit comprises an organic light-emitting diode, and a driving transistor configured to supply current to the organic light-emitting diode. Each driving transistor comprises at least two channels formed therein, wherein the sums of lengths of the at least two channels in each driving transistor of the display are equal.