Pixel Transistor Channel Length and Doping for Display Bezel Reduction
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Solution Overview
Problem
As display devices become smaller, reducing the bezel area to increase the display area is challenging due to limitations in minimizing the size of thin film transistors, which can lead to difficulties in securing driving voltage and shortening the charging time, especially with increasing driving frequency and resolution.
Innovation Solution
The display device incorporates pixel driving and switching transistors with specific active layers doped with group 3 and group 5 elements, featuring different channel lengths and gate insulating layers to secure a wide range of driving voltages and prolong charging time, while also reducing reaction time when turning on/off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the size of thin film transistor is reduced to minimize bezel area, then the display area can be increased, but the driving voltage cannot be secured and the charging time is shortened
Solution Approach 1:
The patent applies local quality by differentiating the active layer doping between two transistor types within the same pixel circuit. The first transistor uses an active layer doped with group 3 element (e.g., boron) to achieve p-type characteristics with higher threshold voltage for stable driving, while the second transistor uses an active layer doped with group 5 element (e.g., phosphorus) to achieve n-type characteristics with lower threshold voltage for faster charging. This localized differentiation allows each transistor to be optimized for its specific function while maintaining compact size.
Solution Approach 2:
The patent changes the doping parameter of the active layer to fundamentally alter the electrical characteristics of the transistors. By selecting group 3 elements for p-type doping and group 5 elements for n-type doping, the threshold voltages and charge characteristics of the transistors are modified to achieve both stable driving voltage and adequate charging time in a reduced-size configuration.
2Area of stationary object
If the size of thin film transistor is reduced to minimize bezel area, then the display area can be increased, but the charging time is shortened
Solution Approach 1:
The patent applies local quality by differentiating the active layer doping between two transistor types within the same pixel circuit. The first transistor uses an active layer doped with group 3 element (e.g., boron) to achieve p-type characteristics with higher threshold voltage for stable driving, while the second transistor uses an active layer doped with group 5 element (e.g., phosphorus) to achieve n-type characteristics with lower threshold voltage for faster charging. This localized differentiation allows each transistor to be optimized for its specific function while maintaining compact size.
Solution Approach 2:
The patent changes the doping parameter of the active layer to fundamentally alter the electrical characteristics of the transistors. By selecting group 3 elements for p-type doping and group 5 elements for n-type doping, the threshold voltages and charge characteristics of the transistors are modified to achieve both stable driving voltage and adequate charging time in a reduced-size configuration.
3Productivity
If the driving frequency or resolution of the display device is increased, then the display quality is improved, but the charging time of the thin film transistor is shortened
Solution Approach 1:
The patent changes the doping parameter of the active layer to fundamentally alter the electrical characteristics of the transistors. By selecting group 3 elements for p-type doping and group 5 elements for n-type doping, the threshold voltages and charge characteristics of the transistors are modified to achieve both stable driving voltage and adequate charging time in a reduced-size configuration.
Solution Approach 2:
The patent employs dynamic operation by using the second transistor with n-type characteristics (doped with group 5 element) specifically for switching operations that require fast charging and discharging. The shorter channel length of the second transistor enables rapid charge accumulation and release, allowing the pixel to respond quickly to successive scan signals at high driving frequencies while maintaining adequate charging time through optimized charge carrier mobility.
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
This configuration ensures stable driving voltages and extended charging times, reducing the reaction time of the transistors, thereby enhancing display quality and minimizing the bezel area.
Implementation Method 1
a first active layer doped with a group 3 element, and including a first channel area having a first length
Data Source
AI summary
A display device includes a pixel including a pixel driving transistor and a pixel switching transistor, the pixel driving transistor including a first active layer including a first channel area having a first length, a first gate insulating layer on the first active layer, a first gate electrode on the first gate insulating layer, a first source electrode and a first drain electrode above the first gate electrode, the pixel switching transistor including a second active layer including a second channel area having a second length that is shorter than the first length, a second gate insulating layer on the second active layer, a second gate electrode on the second gate insulating layer, a second source and a second drain electrode above the second gate electrode, and wherein the pixel driving transistor and the pixel switching transistor each include a P-MOS transistor.