Printed Carbon Nanotube TFT Backplanes for AMOLED Displays
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Solution Overview
Problem
Current thin film transistor (TFT) technologies for display backplanes do not offer a one-size-fits-all solution, and existing methods for printing semiconductor-enriched single-walled carbon nanotubes (SWCNTs) on flexible substrates have not produced fully printed TFTs suitable for display backplanes, lacking the advantages of low-cost, low environmental impact, and high throughput.
Innovation Solution
A method for producing low-voltage SWCNT TFT backplanes using a printing process with liquid-based inks, involving the sequential printing of gold electrodes, insulating layers, semiconducting carbon nanotubes, dielectric materials, gate electrodes, and pixel electrodes, with specific materials and processes such as aerosol jet printing, ink jet printing, or screen printing, to create fully integrated and functional backplanes for active matrix organic light emitting devices (AMOLED) and active matrix liquid crystal displays (AMLCD).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional TFT fabrication methods are used, then manufacturing precision and device performance are achieved, but manufacturing cost increases and environmental impact worsens
Solution Approach 1:
The patent replaces conventional mechanical vacuum deposition and photolithography systems with printing-based fabrication methods. Specifically, it uses inkjet printing to deposit carbon nanotube semiconductors and conductive inks to form electrodes, eliminating the need for expensive vacuum chambers and photolithography equipment while maintaining TFT fabrication precision
Solution Approach 2:
The patent changes the fundamental fabrication parameters from high-vacuum, high-temperature processes to ambient or low-temperature printing processes. Carbon nanotube transistors are fabricated at temperatures below 150°C using printing methods, compared to conventional high-temperature CVD or PVD processes, thereby reducing manufacturing cost and energy consumption
2Reliability
If conventional TFT fabrication methods are used, then device performance is achieved, but productivity decreases due to multiple process steps
Solution Approach 1:
The patent merges multiple conventional fabrication steps into a single printing process. The inkjet printer deposits semiconductors, dielectrics, and conductive materials in sequential layers without requiring separate vacuum deposition, photolithography, and etching steps, thereby maintaining device performance while significantly improving fabrication throughput
Solution Approach 2:
The patent uses self-assembly and spontaneous organization of carbon nanotubes during the printing process to form functional transistor channels. The chiral selection of carbon nanotubes occurs preliminarily through solution processing before deposition, ensuring device performance while reducing subsequent processing steps
3Ease of manufacture
If flexible substrate printing is attempted, then flexibility and low-cost are achieved, but manufacturing precision and device functionality deteriorate
Solution Approach 1:
The patent replaces mechanical alignment systems with digital positioning and software-controlled print head movement. The inkjet printing system uses computer-aided design (CAD) files and precise motor control to achieve sub-10 micrometer pattern registration accuracy on flexible substrates, eliminating mechanical alignment errors
Solution Approach 2:
The patent uses flexible thin-film substrates that maintain dimensional stability during the printing process. The substrate is kept flat and tensioned during inkjet deposition to prevent warping, ensuring manufacturing precision while maintaining flexibility for subsequent bending applications
Data Source
AI summary
The present disclosure provides the ability to produce backplanes for AMLCD and AMOLED. Specifically, each and every component of the backplanes can be printed. Depending on the resolution and screen size of the displays, backplanes can include over a million different components that must be printed that include components of the thin film transistor (TFT) and electrodes to address each of those TFTs. Even a slight misregistry of components during printing can lead to failure of one or more pixels, potentially rendering the entire display unsuitable for use. The present disclosure provides the ability to reproducibly and accurately print each and every component of the backplane for both AMLCD and AMOLED. The ability to completely print backplanes provides numerous advantages, such as reduced costs, improved throughput, more environmental friendliness, and the like.