Multi-Type TFT Backplane for Flexible Displays
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional TFT backplanes using single types of transistors face challenges such as low carrier mobility, display non-uniformity, high power consumption, and complex manufacturing processes, particularly in flexible displays, due to limitations in silicon-based TFTs and oxide TFTs.
Innovation Solution
A multi-type TFT backplane is developed, combining low-temperature polycrystalline silicon (LTPS) TFTs and oxide semiconductor TFTs on the same substrate, where LTPS TFTs are used for driving circuits and oxide TFTs for pixel circuits, with shared gate, source, and drain electrodes, and overlapping active layers to optimize carrier mobility and threshold voltage uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If LIPS TFTs are used in the backplane, then carrier mobility is significantly improved (>100 cm2/V·s), but threshold voltage uniformity deteriorates due to grain boundary variations causing display non-uniformity (mura)
Solution Approach 1:
The patent applies different TFT types to different functional regions: LIPS TFTs are used in driving circuits where high carrier mobility is critical for fast switching and signal processing, while oxide TFTs are used in pixel circuits where threshold voltage uniformity is critical for display quality. This local differentiation resolves the contradiction by optimizing each region for its specific performance requirement.
2Manufacturing precision
If oxide TFTs are used in the backplane, then threshold voltage uniformity is improved, but carrier mobility is limited compared to LIPS TFTs
Solution Approach 1:
The patent strategically places oxide TFTs in pixel circuits where uniform threshold voltage ensures consistent display output across all pixels, while accepting the lower carrier mobility limitation. Meanwhile, LIPS TFTs handle the driving circuits where high-speed operation is prioritized. This spatial separation of functions based on material properties resolves the mobility-uniformity tradeoff.
3Ease of manufacture
If a-Si TFTs are used in the backplane, then manufacturing complexity is reduced and process temperature is lowered for flexible displays, but carrier mobility is insufficient for high-speed drive circuits
Solution Approach 1:
The patent segments the backplane into different functional zones with different TFT types: oxide TFTs are used in regions requiring low-temperature processing and simple manufacturing (such as pixel circuits), while LIPS TFTs are used in driving circuits requiring high carrier mobility. This segmentation allows each region to be optimized independently, resolving the contradiction between ease of manufacture and operational performance.
4Speed
If LIPS TFTs are used for high-speed operation, then drive circuit performance is improved, but power consumption increases due to higher operating currents
Solution Approach 1:
The patent uses LIPS TFTs specifically in driving circuits where high-speed operation is necessary for signal processing and control, while oxide TFTs are used in pixel circuits where low power consumption is more critical. By localizing high-power components only where absolutely necessary, the overall power consumption of the display is reduced while maintaining required drive circuit performance.
Data Source
AI summary
An organic light emitting display is provided. The organic light emitting display comprises a multi-type thin-film transistor (TFT) and an organic light emitting diode. The multi-type TFT has a low-temperature-poly-silicon (LTPS) TFT and an oxide semiconductor TFT (oxide TFT) disposed on the LTPS TFT. The organic light emitting diode is electrically connected to the multi-type TFT. The LTPS TFT and the oxide TFT are connected to the same gate line.