Four-Terminal Driving Transistor for OLED Pixel Circuit Area Reduction
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Solution Overview
Problem
The reduction in size of transistors in organic light emitting display devices due to increased resolution and size leads to degraded driving capacity, resulting in decreased display quality.
Innovation Solution
Incorporating a driving transistor with four independent terminals, including first and second gate electrodes, and applying an independent bias voltage to control the driving voltage range, with a channel length of about 3 μm or less and a bias voltage level of −7 V to 6 V, to enhance the driving capacity and display quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the transistor size is reduced to increase resolution and display size, then the area of the pixel circuit is reduced, but the driving capacity of the transistor deteriorates
Solution Approach 1:
The transistor is divided into four independent terminals including first and second gate electrodes, channel, and source/drain regions. This segmentation allows independent control of different regions, enabling the miniaturized transistor to maintain adequate driving capacity through optimized voltage control in each segment.
Solution Approach 2:
The patent applies specific voltage parameters to the four terminals to control the transistor's driving characteristics. By adjusting the voltage applied to the first gate electrode, second gate electrode, source, and drain, the driving capacity is optimized for the reduced transistor size while maintaining the required pixel circuit area.
2Area of moving object
If the transistor size is reduced, then the pixel circuit area is reduced, but the display quality deteriorates
Solution Approach 1:
The four-terminal transistor structure segments the control functions, allowing precise control of carrier flow in the channel region. This enables high-quality display output even from miniaturized transistors by independently optimizing the electrical characteristics of each terminal.
Solution Approach 2:
Specific voltage parameters are applied to control the transistor operation in the saturation region, ensuring stable and precise current control for high-quality display. The parameter optimization compensates for the reduced transistor size effects on display quality.
3Length of stationary object
If the channel length is reduced to 3 μm or less, then the transistor area is reduced, but the driving voltage range control becomes more difficult
Solution Approach 1:
The channel is controlled by two separate gate electrodes, allowing independent voltage application to each gate. This segmentation enables precise control of the electric field distribution in the short channel, managing the driving voltage range effectively despite the reduced channel length.
Solution Approach 2:
The first and second gate electrodes act as intermediaries between the control circuit and the channel region. By applying voltages through these intermediate gates, the patent achieves precise control over the short channel's electrical characteristics without direct complex control.
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 maintains a sufficient driving voltage range of 2 V to 5 V, improving the display quality by adjusting the sub-threshold voltage slope and ensuring effective operation of the organic light emitting diode across various grayscales.
Implementation Method 1
an organic light emitting diode to emit a light according to a driving current generated from the driving transistor
Data Source
AI summary
An organic light emitting display device may include a display panel, a source driving circuit, and a voltage generator. The display panel may include a pixel circuit including a driving transistor to drive an organic light emitting diode. The driving transistor may have four independent terminals including first and second gate electrodes. The source driving circuit may provide a data voltage to the pixel circuit. The voltage generator may apply an independent bias voltage to the second gate electrode of the driving transistor to control a driving voltage range of the driving transistor.