Purdue University researchers discovered a way to trigger cooperative behavior in organic semiconductors, an energy- and time-saving phenomenon that may help enhance the performance of smartwatches, solar cells, and other organic electronics.

This discovery came from a team of researchers, including Dr. Brett Savoie, a Charles Davidson Associate Professor of Chemical Engineering, and  Dr. Bumjoon Seo, a Post-Doctoral Research Assistant in the Davidson School of Chemical Engineering, in collaboration with the research group of Dr. Ying Diao at the University of Illinois.

Their work will appear in Nature Communications at 10 a.m. GMT/5 a.m. CST Tuesday, March 21, and is associated with the DOI: 10.1038/s41467-023-36871-9.

“We discovered a new conductive material that shows a rapid “cooperative” phase change that changes its dimensions (it shrinks) and conductivity (it gets less conductive). Cooperative transitions are interesting because they happen very quickly and without much energy input,” explained coauthor Brett Savoie. “Theoretically this transition could be as fast as the speed of sound, but in practice it is usually slower because of imperfections. The main near-term applications are using the material as an actuator for robotics or an environmentally responsive circuit element.”  

The researchers discovered that using heat to rearrange the alkyl chains — the clusters of hydrogen and carbon atoms spooling out from the molecule’s core — causes the core itself to tilt, triggering a crystal-wide chain of collapse the researchers refer to as an “avalanche.” This method also caused the crystal itself to shrink. In an electronic device, this translates to a temperature-induced on-off switch.

For a long time, researchers have struggled to manually trigger molecular cooperativity in non-living systems like organic semiconductors. Doing so could help unlock valuable properties in the electronic devices that use them — like the ability to flex without breaking and contour to human skin.

“Our material is also distinct in several other ways,” said Savoie. “It is metal free and also undergoes multiple phase transitions. One of these transitions involves a change in the magnetic state of the material that might also open up new applications.”

An important step for designing dynamic organic electronics is developing dynamic organic semiconductors. And for that to happen, the semiconductor molecules must cooperate.

Coauthors of this work are affiliated with Purdue University, the University of Illinois, the Chinese Academy of Sciences, and Argonne National Laboratory.

Read more about this research at https://beckman.illinois.edu/about/news/article/2023/03/21/molecular-teamwork-makes-the-organic-dream-work

To learn more and request a copy of the manuscript, contact Professor Brett Savoie at bsavoie@purdue.edu