AMOLED Driving TFT Gate Insulator Aperture Ratio
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Solution Overview
Problem
Active matrix organic light emitting diode (AMOLED) displays face challenges in achieving precise gray level control and increasing the pixel aperture ratio due to the area occupied by connection circuitry between thin film transistors (TFTs), which limits the display's efficiency and image quality.
Innovation Solution
The implementation of a driving TFT with a direct electrical connection to the circuit switching TFT, reducing the area occupied by connection circuitry, and incorporating a gate insulator layer and interlayer dielectric to increase the pixel aperture ratio and gray level control by allowing a larger range of voltages to be applied to the gate electrode of the driving TFT.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If connection circuitry between TFTs is extended through the pixel area, then electrical connection is achieved, but the pixel aperture ratio decreases
Solution Approach 1:
The patent moves the connection circuitry from the planar pixel area to a vertical arrangement by extending connections through the gate insulator layer. The circuit switching TFT is positioned in a different layer (over the gate insulator) than the driving TFT, allowing connections to be made in the vertical dimension rather than consuming horizontal pixel area.
2Measurement precision
If the gate voltage range of the driving TFT is increased, then gray level control precision is improved, but the device complexity increases
Solution Approach 1:
The patent divides the voltage regulation function into two separate TFTs: the driving TFT for current regulation and the circuit switching TFT for voltage control. This segmentation allows the circuit switching TFT to extend the gate voltage range without complicating the driving TFT's primary function, enabling precise gray level control through coordinated operation of both transistors.
Data Source
AI summary
Devices and methods for increasing the aperture ratio and providing more precise gray level control to pixels in an active matrix organic light emitting diode (AMOLED) display are provided. By way of example, one embodiment includes disposing a gate insulator between a gate of a driving thin-film transistor and a gate of a circuit thin-film transistor. The improved structure of the display facilitates a higher voltage range for controlling the gray level of the pixels, and may increase the aperture ratio of the pixels.