OLED Pixel Circuit Dual Gate Transistor Voltage Adjustment
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Solution Overview
Problem
In OLED displays, achieving a wide operation range of OLEDs to produce grayscale colors is challenging due to the limited space for pixel circuits, making it difficult to increase the channel length of driving transistors, and thus, alternative methods to reduce the slope of the drain current graph are necessary.
Innovation Solution
A pixel circuit design that includes a driving transistor with a second gate electrode receiving DC power, allowing for precise adjustment of the gate voltage, which reduces the drain current without increasing the channel length, thereby securing an operation range for the OLED.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the channel length of the driving transistor is increased to reduce drain current and secure OLED operation range, then the OLED operation range is improved, but the pixel area increases which is incompatible with high resolution displays
Solution Approach 1:
The gate electrode of the driving transistor is divided into two separate gate electrodes (first gate electrode and second gate electrode) that can be independently controlled. This segmentation allows independent optimization of different transistor functions: one gate controls the main current while the other adjusts threshold voltage to compensate for aging and ensure stable OLED operation without increasing channel length
Solution Approach 2:
The invention changes the electrical parameters of the driving transistor by applying different voltages to the two gate electrodes. By adjusting the voltage on the second gate electrode, the threshold voltage of the transistor is dynamically modified to maintain proper drain current levels and secure the OLED operation range without requiring physical changes to the transistor dimensions
2Reliability
If the channel length of the driving transistor is increased to reduce the slope of drain current graph, then the OLED operation range is secured, but the pixel circuit space is insufficient for high resolution displays
Solution Approach 1:
The gate electrode is segmented into two independently controllable gates, allowing separate optimization of current control and threshold voltage adjustment functions. This enables proper drain current characteristics and OLED operation range without requiring increased channel length, thus fitting within high resolution pixel constraints
Solution Approach 2:
Instead of solving the problem by extending the channel length in one dimension, the invention adds another dimension of control by introducing a second gate electrode. This dual-gate structure provides an additional control parameter that allows achieving the desired drain current characteristics without increasing the physical footprint of the pixel circuit
Data Source
AI summary
A pixel of an OLED display is disclosed. A gate voltage of a driving transistor can be precisely adjusted using a second gate electrode that can supply DC power easily securing an operation range of an OLED. Further, by only adding one power line that can precisely adjust a gate voltage of a driving transistor to an OLED display, an operation range of the OLED can be easily secured and thus a drain current can be reduced without increasing a channel length of the driving transistor resulting in a narrower pixel area. According to various embodiments, the pixel can secure an operation range of the OLED by reducing a magnitude of a drain current by adjusting a gate voltage of a driving transistor.