Prof Jonathan Coleman has fabricated printed transistors consisting entirely of 2-dimensional nanomaterials for the first time. Credit: AMBER, Trinity College Dublin

Researchers may have unlocked several new applications in printed electronics, creating fabricated printed transistors consisting entirely of 2D nanomaterials.

Researchers at AMBER (Advanced Materials and BioEngineering Research) in Ireland, created low-cost thin-film transistors (TFTs) from networks of exfoliated dispersions of 2D materials with graphene contacts. This technology could help develop new applications in a number of ways, including developing food packaging that displays a digital countdown to warn you of spoiling, wine labels that alert you when your white wine is at its optimum temperature, or even a windowpane that shows the day’s forecast.

The discovery also opens the path for industries to cheaply print a bevy of electronic devices— from solar cells to LEDs— with applications from interactive smart food and drug labels to next-generation banknote security and e-passports.

“In the future, printed devices will be incorporated into even the most mundane objects such as labels, posters and packaging,” professor Jonathan Coleman, who is an investigator in AMBER and Trinity's School of Physics, said in a statement. “Printed electronic circuitry [constructed from the devices we have created] will allow consumer products to gather, process, display and transmit information: for example, milk cartons could send messages to your phone warning that the milk is about to go out-of-date.”

According to Coleman, 2D nanomaterials can compete with the materials currently being used for printed electronics.

“Compared to other materials employed in this field, our 2D nanomaterials have the capability to yield more cost effective and higher performance printed devices,” he said. “However, while the last decade has underlined the potential of 2D materials for a range of electronic applications, only the first steps have been taken to demonstrate their worth in printed electronics.”

Coleman explained the importance of the discovery.

“This publication is important because it shows that conducting, semiconducting and insulating 2D nanomaterials can be combined together in complex devices,” he said. “We felt that it was critically important to focus on printing transistors as they are the electric switches at the heart of modern computing.

“We believe this work opens the way to print a whole host of devices solely from 2D nanosheets,” he added.

Coleman worked in collaboration with the groups of professor George Duesberg of AMBER and professor Laurens Siebbeles of Delft University of Technology to use standard printing techniques that combine graphene nanosheets as the electrodes with two other nanomaterials—tungsten diselenide and boron nitride—as the channel and separator to form an all-printed, all-nanosheet, working transistor.

According to the study, the researchers used electrolytic gating to demonstrate all-printed, vertically stacked transistors with graphene source, drain and gate electrodes, a transition metal dichalcogenide channel and a boron nitride separator, all formed from nanosheet networks.

Over the last three decades printable electronics have developed mainly on printable carbon-based molecules, which can be easily turned into printable inks, but are somewhat unstable and have well-known performance limitations.

While there have been several attempts to surpass these obstacles using alternative materials including carbon nanotubes or inorganic nanoparticles, these materials have also shown limitations in either performance or in manufacturability.

The performance of printed 2D devices cannot yet compare with advanced transistors but the researchers said there is a wide scope to improve performance beyond the current state-of-the-art for printed transistors.

The ability to print 2D nanomaterials is based on Coleman’s scalable method of producing 2D nanomaterials, including graphene, boron nitride and tungsten diselenide nanosheets in liquids.

The nanosheets are flat nanoparticles that are a few nanometers thick but hundreds of nanometers wide.

Nanosheets made from different materials have electronic properties that can be conducting, insulating or semiconducting and include all the building blocks of electronics.

Particularly advantageous is liquid processing because it can yield large quantities of high quality 2D materials in a form that is easy to process into inks.

The study was published in Science.