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November 30, 2011

UCLA researchers demonstrate fully printed carbon nanotube transistor circuits for displays

Researchers from Aneeve Nanotechnologies, a startup company at UCLA's on-campus technology incubator at the California NanoSystems Institute (CNSI), have used low-cost ink-jet printing to fabricate the first circuits composed of fully printed back-gated and top-gated carbon nanotube–based electronics for use with OLED displays.

The team made carbon nanotube thin-film transistors with high mobility and a high on–off ratio, completely based on ink-jet printing. They demonstrated the first fully printed single-pixel OLED control circuits, and their fully printed thin-film circuits showed significant performance advantages over traditional organic-based printed electronics.

Ink-jet-printed circuit

Nanoletters - Fully Printed Separated Carbon Nanotube Thin Film Transistor Circuits and Its Application in Organic Light Emitting Diode Control






The advantages of printed electronics and semiconducting single-walled carbon nanotubes (SWCNTs) are combined for the first time for display electronics. Conductive silver ink and 98% semiconductive SWCNT solutions are used to print back-gated thin film transistors with high mobility, high on/off ratio, and high current carrying capacity. In addition, with printed polyethylenimine with LiClO4 as the gating material, fully printed top-gated devices have been made to work as excellent current switches for organic light emitting diodes (OLEDs). An OLED driving circuit composed of two top-gated fully printed transistors has been fabricated, and the successful control over external OLED is demonstrated. Our work demonstrates the significant potential of using printed carbon nanotube electronics for display backplane applications.

"This is the first practical demonstration of carbon nanotube–based printed circuits for display backplane applications," said Kos Galatsis, an associate adjunct professor of materials science at UCLA Engineering and a co-founder of Aneeve. "We have demonstrated carbon nanotubes' viable candidacy as a competing technology alongside amorphous silicon and metal-oxide semiconductor solution as a low-cost and scalable backplane option."

This distinct process utilizes an ink-jet printing method that eliminates the need for expensive vacuum equipment and lends itself to scalable manufacturing and roll-to-roll printing. The team solved many material integration problems, developed new cleaning processes and created new methods for negotiating nano-based ink solutions.

For active-matrix OLED applications, the printed carbon nanotube transistors will be fully integrated with OLED arrays, the researchers said. The encapsulation technology developed for OLEDs will also keep the carbon nanotube transistors well protected, as the organics in OLEDs are very sensitive to oxygen and moisture.

9 pages of supplemental information

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