Printed CNT transistor circuits may lead to cheaper OLED displays

Printed CNT transistor circuits may lead to cheaper OLED displays
(Left) The fully printed back-gated SWCNT thin-film transistor printed on silicon dioxide. (Right) The fully printed top-gated SWCNT thin-film transistor printed on flexible Kapton. Image credit: Pochiang Chen, et al. ©2011 American Chemical Society

( -- While flexible OLED displays have begun appearing in some cell phones, the technology is still too expensive to be widely used in consumer electronics. In one of the latest attempts to enable low-cost mass-production of OLED displays, researchers have fabricated the first complete thin-film transistor circuits printed with a carbon nanotube (CNT) solution for use with display electronics. They found that these circuits are not only easy to fabricate, but they also work as excellent current switches when connected to OLEDs.

The printed transistor circuits were developed by a team of researchers at the University of California at Los Angeles (UCLA); Aneeve Nanotechnologies, a start-up company at UCLA; and the University of Southern California, Los Angeles. Their work is published in a recent issue of .

Although other groups have printed CNT transistors, this is the first time that researchers have successfully printed the complete transistor circuitry: not just the CNTs, but also the metals, polymers, and all other components. In doing so, the work demonstrates for the first time that a fully printed CNT process can be used to fabricate a complete circuit.

Fully printed CNT transistors satisfy two key issues for mass-producing OLED displays at a low cost: they use an inexpensive, fast, and simple process (ink-jet printing), and they use materials with favorable (CNTs).

“CNTs are more stable compared to other organic semiconductor materials,” coauthor Kosmas Galatsis from Aneeve Nanotechnologies and UCLA told “They have superior electronic properties and transistor performance.”

To print back-gated thin-film transistors, the researchers used a commercial silver nanoparticle solution to print the source and drain electrodes. Using a recipe for a semiconductive single-walled CNT (SWCNT) solution that they previously developed, they printed the channel. Tests showed that these printed SWCNT transistors show a similar performance to that of SWCNT transistors fabricated with more expensive photolithographic techniques.

In the second part of their study, the researchers connected two printed SWCNT to an OLED and used them to switch the OLED on and off. The transistor’s good current carrying capacity and other electrical characteristics allow for a dense integration of pixels and low power consumption, making it an ideal component for OLED display backplanes.

By adding a layer of polyethylenimine with LiClO4 to the top of the on the back-gated SWCNT transistor, the researchers could fabricate a top-gated transistor. Then they printed this transistor on flexible Kapton material, demonstrating the potential of using it for flexible electronics.

As the first demonstration of printing a SWCNT solution to make complete transistor circuits for OLED displays, the results of the study suggest that carbon nanotube-based electronics could provide a way to bring OLED displays closer to mass commercialization.

“Our plans are to continue to develop this process for scalability and manufacturing,” Galatsis said. “We plan to be printing products in two years. Commercialization will need to take place with a larger manufacturing partner.”

Explore further

Researchers demonstrate fully printed carbon nanotube transistor circuits for displays

More information: Pochiang Chen, et al. “Fully printed Separated Carbon Nanotube Thin Film Transistor Circuits and Its Application in Organic Light Emitting Diode Control.” Nano Letters. DOI: 10.1021/nl202765b
Journal information: Nano Letters

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Dec 06, 2011
I love the end of the line research articles like this, where the researchers are dusting off their hands and saying, "Well, we're done with this project. let's take it to the factories now."

Finally, some amazing sounding work that will get out of the gate soon, rather than dissappear due to impracticality.

Dec 09, 2011
Have anyone notice lately that 90% of materials researches done in the US or elsewhere as reported on PhysOrg are done mostly by Chinese (name/born/naturalized/origin citizen/leading/collaborating) scientists?

Dec 09, 2011
Have anyone notice lately that 90% of materials researches done in the US or elsewhere as reported on PhysOrg are done mostly by Chinese (name/born/naturalized/origin citizen/leading/collaborating) scientists?
Of course, this is just a consequence of free-market economy. The Chinese are intelligent, cheap workers and the research labs are using this feature willingly. As the result, whole USA is losing brains and money, because most of these people are returning to China after studies, when they're building the competition for USA industry. This is because the free market economy can balance local equilibria well, but it's incompetent regarding the solving of these global ones, which cannot be expressed in money so easily (like the environmental crisis or AGW). Note that in the another areas of physics the ratio of Chinese is much lower, because these areas cannot be monetized so easily. The socialistic China has simply more effective strategy in this point.

Dec 09, 2011
Have anyone notice lately that 90% of materials researches done in the US or elsewhere as reported on PhysOrg are done mostly by Chinese

Have you looked at the honor rolls on US high schools for the past 30 years? Are you really surprised to see asian names pop up in top level research all the time?

The difference is that asians don't take anything for granted. They get taught that to be good at anything you have to apply yourself. American kids tend to think that they are entitled to everything just because they are born American
(hmm...where in history have we heard that kind of thinking before, I wonder?)

Dec 09, 2011
The transfer of industrial production into China is very dangerous for Western countries not just because of gradual lost of job opportunities, but because they're losing continuity in further applied research. It's like the sport training: if you're not dealing with some activity, then you're losing training in it, no matter how strong and clever you are. From the same reason the Russian spaceprobes are falling from sky like apricots from trees, because the Russians did lost the continuity in technical development in this area. It takes years to restore this qualification, because under normal circumstances the younger researchers are learning from these older ones. But who the new generation of USA scientists will learn from? Now you can just speculate, if the artificial keeping of continuity in research is leftwind or rightwind politics, but I do presume, it's simply rational one.

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