First inkjet-printed carbon nanotube circuit

The advantages of printed electronics and semiconducting carbon nanotubes have been combined for display electronics for the first time.

Ink-jet-printed circuit (Credit: UCLA CNSI)

Researchers at Aneeve Nanotechnologies, a startup company at UCLA, have used inkjet printing to fabricate the first fully printed carbon nanotube–based circuit for use with organic light-emitting diodes (OLED) displays.

For the first time, claim the researchers, the advantages of printed electronics and semiconducting single-walled carbon nanotubes (SWCNT) have been combined for display electronics.

The team built the OLED circuit using two top-gated fully printed transistors with high mobility, high on/off ratio, and high current-carrying capacity. The printed single-pixel OLED control circuits and the fully printed thin-film circuits showed significant performance advantages over traditional organic-based printed electronics.

"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," he added.

The researchers say their distinct inkjet printing method eliminates the need for expensive vacuum equipment and lends itself to scalable manufacturing and roll-to-roll printing.

Carbon nanotube thin film transistor circuits (Credit: ACS Publications)

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

Printed electronics are gaining industry-wide traction primarily because of their cost advantage over conventional integrated electronics. They are used in a variety of applications, including displays, RFID, sensors, and batteries.

OLEDs, meanwhile, are slowly displacing LCDs in everything from television and computer screens to smartphones and watches because they are better in almost every respect. Holding back adoption, however, is cost. It is difficult to incorporate thin-film transistors at scale into the OLED production process. The new printed carbon nanotube-based approach to building circuits for OLEDs could lead to an uncomplicated and low-cost method with high production volume. Aneeve is banking on it.

The research was published this month in the journal Nano Letters and can be downloaded here: Fully Printed CNT for Display Paper – ACS Nanoletters (PDF).


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