Oxide TFT Array Layout for OLED Sub-Pixel Color Stability
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Solution Overview
Problem
Organic light emitting display devices face challenges in expressing accurate colors at low gray scales due to leakage currents and threshold voltage changes in driving thin film transistors, leading to color deviations over time.
Innovation Solution
A thin film transistor array substrate with an oxide semiconductor pattern is designed, featuring different channel width-to-length ratios for red, green, and blue sub-pixels to minimize color deviation, and includes a structure that blocks leakage currents and maintains a stable threshold voltage, ensuring accurate color reproduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional thin film transistor is used in the driving TFT, then the device complexity is reduced, but leakage current increases and threshold voltage stability deteriorates
Solution Approach 1:
The patent changes the material parameter of the semiconductor layer from conventional amorphous semiconductor to oxide semiconductor, which fundamentally alters the electrical characteristics to achieve lower leakage current and higher threshold voltage stability
Solution Approach 2:
The patent employs a composite structure combining oxide semiconductor material with specific insulating materials (such as silicon oxide, silicon nitride) to create a transistor that leverages the unique properties of oxide semiconductors while maintaining manufacturing compatibility
2Manufacturing precision
If the channel width-to-length ratio is made uniform across all sub-pixels, then the manufacturing precision is improved, but color accuracy deteriorates due to threshold voltage changes over time
Solution Approach 1:
The patent applies different channel width-to-length ratios to different sub-pixels (red, green, blue) based on their specific characteristics and degradation patterns, allowing each sub-pixel to be optimized locally rather than using a uniform design across all pixels
Solution Approach 2:
The patent varies the geometric parameters (channel width and length) of different sub-pixels to compensate for differential threshold voltage shifts that occur during device operation and aging, thereby maintaining color accuracy over time
3Reliability
If the oxide semiconductor pattern is used in the driving TFT, then the leakage current is reduced and threshold voltage stability is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent modifies the material composition parameter of the semiconductor layer to use oxide semiconductor, which provides inherently lower leakage current and better threshold voltage stability while maintaining compatibility with existing thin film transistor manufacturing processes
Data Source
AI summary
A thin film transistor array substrate of the present disclosure includes a substrate including an active area and a non-active area disposed in the vicinity of the active area, and a plurality of pixels disposed in the active area, in which each pixel includes a plurality of sub pixels, each sub pixel includes a driving thin film transistor including an oxide semiconductor pattern, and the driving thin film transistor in the pixel includes sub pixels having different ratios of a width to a length of a channel of the driving thin film transistor. By doing this, provided is a display device in which a color deviation between each sub pixels, as it is used, is reduced to stabilize a color of the display device.