Pixel Circuit Bias Electrode Layout for Wider Grayscale Range
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Solution Overview
Problem
Existing display technologies face challenges in accurately expressing grayscale levels due to limited voltage ranges of data signals, which affects the reliability of achieving desired luminance in display devices.
Innovation Solution
Incorporating a diode-connected transistor with a lower electrode supplied by a bias voltage and using oxide semiconductors in the transistors, along with a bias voltage generator outside the display panel to provide a bias voltage, which increases the subthreshold swing and widens the voltage range for data signal expression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional transistor configuration is used without a lower electrode, then the device structure is simpler, but the subthreshold swing is insufficient and the voltage range for data signal expression is limited
Solution Approach 1:
The transistor structure is segmented into multiple functional components: a gate electrode for voltage control, a lower electrode for bias voltage application, and an active layer for current conduction. This segmentation allows independent optimization of each component's function, enabling the lower electrode to provide bias voltage that increases subthreshold swing without compromising the gate's control capability, thus resolving the contradiction between structural simplicity and luminance expression reliability
Solution Approach 2:
The lower electrode acts as an intermediary element between the bias voltage source and the active layer. It receives bias voltage from an external source and transmits it to the active layer to modulate the transistor's subthreshold characteristics. This intermediary function enables independent control of the subthreshold swing parameter, allowing the voltage range for data signal expression to be widened without directly complicating the core transistor structure
2Measurement precision
If the voltage range of data signals is limited, then the device complexity is lower, but the grayscale representation accuracy is insufficient
Solution Approach 1:
The invention changes the electrical parameters of the transistor by applying a bias voltage to the lower electrode. This parameter change increases the subthreshold swing, which in turn widens the voltage range available for data signal expression. By modifying the transistor's electrical characteristics rather than adding complex voltage generation circuits, the system achieves improved grayscale representation accuracy without proportionally increasing device complexity
Solution Approach 2:
The lower electrode enables dynamic adjustment of the transistor's operating characteristics through external bias voltage control. This dynamic control allows the subthreshold swing to be adjusted in real-time, providing flexibility in optimizing the voltage range for data signals. The dynamic capability enables the system to adapt to different display requirements without requiring a fundamentally more complex device architecture
Data Source
AI summary
A pixel is disclosed that includes a light emitting element, a pixel circuit, and a transistor. The light emitting element is electrically connected between a first node and a second power line. The pixel circuit is electrically connected between a second node and the first node, and includes a first transistor configured to control current flowing from the second node to the first node in response to a data signal. A transistor is electrically connected between a first power line and the first transistor, and includes a gate electrode electrically connected to the first power line. The transistor further includes a lower electrode disposed opposite the gate electrode with an active layer of the transistor interposed therebetween. The lower electrode is configured to receive a bias voltage.