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Controlling chain conformations to enhance electronic devices

Thursday, December 1, 2016
A fluorinated polymer with a high dielectric constant is demonstrated within thin-film transistors. Crosslinking polymer chains reduces energetic disorder at the insulator–semiconductor interface, resulting in an increase in the charge mobility of rubrene single-crystal field-effect transistors. Image: Enrique Gomez / Penn State

Controlling the way fluorinated polymer chains twist and turn may enable fast and flexible electrical circuits, according to collaborative research conducted at Penn State. The findings may offer substantial impact on the development of new polymer-type materials used in flexible electronic applications.

Organic thin film transistors (OTFTs), which integrate organic semiconducting compounds in electronic components, have the potential to revolutionize the field of flexible electronics by generating bendable and foldable devices that act as electronic circuits. OTFTs are the building blocks of more complicated circuits and serve as the "on" and "off" switches between various electronic states. They are comprised of multiple layers, including a dielectric layer — which functions as an insulator — responsible for inducing charge.

"Our work aims to introduce new, more stable polymers into electrical circuits without negatively impacting performance," said Enrique Gomez, associate professor of chemical engineering, Penn State. "By controlling the way that polymer chains twist and bend at a molecular level in OTFTs, we have found that we are able to break the universal relationship between charge mobility of the semiconductor and charge storage capacity of the dielectric layer, providing a basis to create fast and reliable circuits from organic materials."

Controlling the order and arrangement of polymer chains along the semiconductor interface is the key in breaking the relationship, according to research published in Advanced Materials.

Polymers are capable of storing large amounts of electrical energy in the insulator, however, it is known that electrical energy slows as it travels through semiconducting materials. The hope is that new findings about the inverse relationship will lead to the development of fast organic devices with the capacity to revolutionize the flexible electronics industry.