Pixel Circuit Merging Transistors for OLED Leakage Reduction
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Solution Overview
Problem
The application of high-resolution panels in organic light emitting display devices is limited due to the increased number of transistors in each pixel, which complicates the display's ability to achieve desired luminance and efficiency.
Innovation Solution
A display device with a pixel configuration that includes specific transistors and a storage capacitor, where the third transistor is an N-type oxide semiconductor thin film transistor, reducing leakage current and allowing for a more compact pixel design by eliminating the need for additional initialization transistors, and utilizing P-type Low-Temperature Poly-Silicon (LTPS) thin film transistors for other transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If more transistors are included in a single pixel to compensate for threshold voltage deviation, then the threshold voltage compensation is improved, but the pixel area increases and application to high resolution panels is limited
Solution Approach 1:
The initialization transistor and the third transistor are merged into a single transistor component. This merged transistor performs dual functions: initializing the third node during the non-emission period and acting as the third transistor during the emission period, thereby eliminating the need for separate initialization and third transistors in the pixel circuit
Solution Approach 2:
The merged transistor serves multiple functions across different time periods: it acts as an initialization transistor connected to the third power source during the non-emission period, and as the third transistor connected to the light emitting diode during the emission period. This multi-functionality reduces the total transistor count while maintaining all necessary circuit functions
2Ease of operation
If additional initialization transistors are added to initialize the third node, then the initialization function is improved, but the device complexity and area increase
Solution Approach 1:
The initialization transistor and the third transistor are merged into a single transistor component. This merged transistor performs dual functions: initializing the third node during the non-emission period and acting as the third transistor during the emission period, thereby eliminating the need for separate initialization and third transistors in the pixel circuit
Solution Approach 2:
The merged transistor operates in different modes during different time periods: during the non-emission period it functions as an initialization transistor to reset the third node, and during the emission period it functions as the third transistor to control current to the light emitting diode. This periodic switching of functions eliminates the need for separate dedicated initialization and third transistors
3Ease of manufacture
If P-type LTPS thin film transistors are used for most transistors, then the manufacturing process is simplified, but leakage current increases compared to N-type oxide semiconductor transistors
Solution Approach 1:
Different transistor types are strategically assigned to different circuit positions based on their electrical characteristics: N-type oxide semiconductor transistors with low leakage current are used for the fourth transistor controlling the light emitting diode and the merged transistor, while P-type LTPS transistors are used for other transistors where higher current handling is needed. This local differentiation optimizes both performance and manufacturability
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 reduces power consumption and allows for a higher resolution display by minimizing leakage current and area usage, enabling the display device to achieve desired luminance and efficiency.
Implementation Method 1
wherein the third transistor is an N-type oxide semiconductor thin film transistor
Implementation Method 2
the organic light emitting diode includes an emissive electroluminescent layer of an organic compound that emits light in response to electric current
Data Source
AI summary
A display device including: a pixel connected to first, second and third scan lines, a data line, and an emission line, the pixel including: an LED; a first transistor including a first electrode connected to a first node, a second electrode connected to a second node, and a gate electrode connected to a third node; a second transistor connected between the data line and the first node and including a gate electrode connected to the first scan line; a third transistor connected between the second node and the third node and including a gate electrode connected to the second scan line; a fourth transistor connected between the second node and a power source and including a gate electrode connected to the third scan line; and a fifth transistor connected between the second node and an anode of the LED and including a gate electrode connected to the second scan line.