OLED Driving TFT Aspect Ratios for Afterimage Reduction
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Solution Overview
Problem
Thin-film transistors made by low-temperature polysilicon technology in OLED panels exhibit serious hysteresis effects, leading to fluctuations in output current and resulting in afterimages, particularly in green and red images under the same gray scale.
Innovation Solution
The display panel incorporates driving thin-film transistors with specific aspect ratios for channel portions and capacitors, where the first driving thin-film transistor has a smaller aspect ratio than the second, connected to green and non-green OLED devices respectively, to alleviate afterimage phenomena by adjusting electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thin-film transistors are made by low-temperature polysilicon technology, then manufacturing cost and ease of manufacture are improved, but hysteresis effects increase causing output current fluctuations and afterimages
Solution Approach 1:
The patent applies different aspect ratios to different thin-film transistors based on their specific functions and the color of OLED devices they control. The first driving TFT has a first aspect ratio while the second driving TFT has a second aspect ratio, allowing each transistor to be optimized for its specific role in compensating for hysteresis effects and stabilizing output current for different color channels.
Solution Approach 2:
The patent changes the aspect ratio parameter of the thin-film transistors to optimize performance. By adjusting the aspect ratio (width-to-length ratio of the channel), the patent compensates for hysteresis effects in low-temperature polysilicon TFTs and stabilizes the output current, thereby reducing afterimages while maintaining ease of manufacture.
2Device complexity
If uniform aspect ratios are used for all driving transistors, then device complexity is reduced, but afterimage phenomena increase due to hysteresis effects
Solution Approach 1:
The patent implements local quality by assigning different aspect ratios to different driving TFTs based on their specific functions and the OLED color channels they control. This localized optimization allows each transistor to compensate for hysteresis effects appropriate to its role, reducing afterimage phenomena while keeping the overall device design relatively simple and manageable.
3Reliability
If aspect ratio is optimized to reduce hysteresis effects, then output current stability is improved, but transistor area increases affecting pixel density
Solution Approach 1:
The patent optimizes the aspect ratio parameter (width-to-length ratio) of the thin-film transistors to reduce hysteresis effects and stabilize output current. By carefully selecting specific aspect ratio values, the patent achieves current stability while controlling the overall transistor area to maintain acceptable pixel density in the display panel.
Data Source
AI summary
The present invention provides a display panel. In the display panel, a first driving thin-film transistor is electrically connected to a first organic light-emitting diode (OLED) device, and a second driving thin-film transistor is electrically connected to a second organic light-emitting diode (OLED) device; the first driving thin-film transistor includes a first active layer, and a channel portion of the first active layer has a first aspect ratio; the second driving thin-film transistor includes a second active layer, and a channel portion of the second active layer has a second aspect ratio; and the first aspect ratio is smaller than the second aspect ratio.