A team from the U.S. Department of Energy’s National Accelerator Laboratory and Stanford University, Calif., have developed a printing process they call FLUENCE-fluid-enhanced crystal engineering-that for some materials results in thin films capable of conducting electricity ten times more efficiently than those made by conventional methods. The printing method is fast and works with a variety of organic materials.
“Even better, most of the concepts behind FLUENCE can scale up to meet industry requirements,” said Ying Diao, a Stanford Linear Accelerator Center (SLAC) postdoctoral researcher and lead author of the study, which appeared in Nature Materials (“Solution coating of large-area organic semiconductor thin films with aligned single-crystalline domains”).
Stefan Mannsfeld, a SLAC materials physicist and one of the principal investigators of the experiment, said the key was to focus on the physics of the printing process rather than the chemical makeup of the semiconductor. Diao engineered the process to produce strips of big, neatly aligned crystals that electrical charge can flow through easily, while preserving the benefits of the “strained lattice” structure and “solution shearing” printing technique previously developed in the lab of Mannsfeld’s co-principal investigator, Professor Zhenan Bao of the Stanford Institute for Materials and Energy Sciences, a joint SLAC-Stanford institute.
To make the advance, Diao focused on controlling the flow of the liquid in which the organic material is dissolved. “It’s a vital piece of the puzzle,” she said. If the ink flow does not distribute evenly, as is often the case during fast printing, the semiconducting crystals will be riddled with defects. “But in this field there’s been little research done on controlling fluid flow.”
