Thin Film Transistor Bias Terminal for OLED Hysteresis Control
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Solution Overview
Problem
Organic light emitting diode (OLED) displays suffer from motion blur due to the hysteresis characteristic of driving transistors, which affects the display of clear images, especially when transitioning between grayscale levels, leading to incomplete luminance representation.
Innovation Solution
A thin film transistor with a bias terminal connected to the channel region between the source and drain terminals is introduced, allowing for improved hysteresis characteristics by applying an assistance voltage during the initialization period, thereby reducing the hysteresis effect and enhancing grayscale transition accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional driving transistor without a bias terminal is used, then the device complexity is low, but motion blur occurs due to hysteresis characteristics during grayscale transitions
Solution Approach 1:
The transistor is segmented into four terminals: source, drain, gate, and bias terminal. The bias terminal is separately connected to the channel region, allowing independent control of the channel potential. This segmentation enables the bias terminal to specifically address the hysteresis issue without redesigning the entire transistor structure.
Solution Approach 2:
The bias terminal acts as an intermediary element that mediates the hysteresis effect by providing an additional control point on the channel region. By applying a bias voltage through this intermediary terminal, the channel potential can be adjusted to compensate for hysteresis, improving grayscale transition accuracy without directly modifying the source-drain-gate operation.
2Speed
If the current amount is quickly changed from low grayscale to high grayscale, then the response speed is improved, but the hysteresis characteristic causes delayed response and motion blur
Solution Approach 1:
The bias terminal enables preliminary action by allowing the channel potential to be pre-adjusted before the main grayscale transition occurs. During initialization or before rapid grayscale changes, a bias voltage can be applied to prepare the channel for the upcoming transition, reducing the hysteresis-induced delay and ensuring more accurate response to rapid grayscale changes.
Solution Approach 2:
The transistor structure is made dynamic by adding the bias terminal, which allows the channel potential to be dynamically adjusted during operation. This dynamic control enables the transistor to adapt to rapid grayscale transitions by modulating the channel conductivity in real-time, improving both response speed and grayscale accuracy simultaneously.
3Reliability
If a bias terminal is added to the transistor, then the hysteresis characteristic is improved and motion blur is reduced, but the device complexity increases
Solution Approach 1:
The bias terminal provides local quality improvement by specifically targeting the channel region where hysteresis occurs. Instead of redesigning the entire transistor, the bias terminal locally enhances the control capability at the channel, providing precise grayscale transition accuracy only where needed without unnecessarily complicating other parts of the device.
Data Source
AI summary
A thin film transistor, a pixel, and an organic light emitting diode (OLED) display including the same are disclosed. The thin film transistor includes a connection to the channel region separate from connections to the source and drain.