Flat Panel Display With Differentiated TFT Body Contacts
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Solution Overview
Problem
Conventional AMOLED displays face a trade-off between high-speed operating characteristics and the lifetime of EL elements, where high-resolution displays with polysilicon thin film transistors in both pixel and driving circuit portions either exceed current limits, leading to short lifetimes or fail to support high-speed operation due to low on-current characteristics.
Innovation Solution
The use of thin film transistors with different body contact structures in the pixel and driving circuit portions, where pixel portions employ source-body contact transistors for uniform current and driving circuit portions use gate-body contact transistors for low voltage ON/OFF characteristics, allowing for high-speed operation while maintaining extended EL element lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If polysilicon thin film transistors are used in both pixel portion and driving circuit portions to achieve high-speed operation, then operating speed is improved, but on-current becomes excessively high causing EL element lifetime to deteriorate
Solution Approach 1:
The patent applies different body contact configurations to thin film transistors in different functional regions: source-body contact for pixel portion TFTs to limit on-current and protect EL elements, while gate-body contact for driving circuit TFTs to enable high-speed operation. This local differentiation resolves the contradiction by optimizing each region for its specific function.
2Duration of action of stationary object
If thin film transistors with low mobility are used to maintain suitable on-current characteristic, then EL element lifetime is improved, but operating speed deteriorates
Solution Approach 1:
The patent implements local quality differentiation by using source-body contact TFTs in pixel portions where current control is critical for EL element protection, while employing gate-body contact TFTs in driving circuit portions where high-speed operation is prioritized. Each configuration is locally optimized for its functional requirements.
3Ease of manufacture
If uniform thin film transistor structure is used throughout the display to simplify manufacturing, then manufacturing complexity is reduced, but performance optimization for different functions is compromised
Solution Approach 1:
The patent applies local quality by differentiating body contact configurations between pixel portion TFTs and driving circuit TFTs. While this increases manufacturing complexity compared to a uniform structure, it enables optimized performance for each functional region, achieving better overall device performance and longevity.
Data Source
AI summary
A high-speed flat panel display having a long lifetime. Thin film transistors in a pixel portion having a plurality of pixels are contacted differently from thin film transistors in driving circuit portions for driving the pixels, thereby enhancing luminance uniformity and reducing power consumption. The thin film transistors each have a channel region and a body contact region for applying a predetermined voltage to the channel region. At least one thin film transistor in the pixel portion is a source-body contact thin film transistor having the body contact region connected to one of source and drain electrodes so that the predetermined voltage can be provided to the channel region. Each thin film transistor in the driving circuit portion is a gate-body contact thin film transistor having the body contact region connected to the gate electrode so that a predetermined voltage can be provided to the channel region.