An organic semiconductor crystallizes between metal contacts (top). Without a pretreatment, the material does not crystallize (bottom).
Organic materials crystallize on a flexible chip for high-performance electronics
Source: “Contact-Induced Crystallinity for High-Performance Soluble Acene-Based Transistors and Circuits”
David Gundlach et al.
Nature Materials 7: 216-221
Results: Researchers at the National Institute of Standards and Technology, Penn State University, and the University of Kentucky have developed a chemical process that helps molecules of an organic semiconductor form transistors on a flexible electronic chip. The molecules crystallize only in the areas between electrical contacts, bridging the gaps between them. In other areas, the organic semiconductor does not crystallize, instead acting as an electrical insulator that prevents unwanted cross talk between transistors.
Why it matters: The process could provide a cheaper way to make high-performance, flexible electronics. Current techniques require either precisely printing semiconductors onto a flexible surface or depositing a semiconductor and etching circuitry into it. Now either step can be skipped. The semiconductor can simply be deposited across the entire surface, and it will self-organize to take on different electronic properties in the appropriate areas.
Methods: The researchers use conventional methods to deposit metallic electrodes on a flexible polyimide substrate. Then they dip the substrate in pentafluorobenzene thiol, which sticks only to the electrodes. Next, they layer the entire surface with an organic semiconductor solution. As the solution dries, it crystallizes on or near the thiol-coated electrodes.
Next steps: The researchers will continue to study the chemistry and kinetics of the semiconductor to better understand what causes it to crystallize. They are also trying to duplicate the process using other semiconductor materials.