University of Oregon chemists have synthesized organic molecular structures that move both positive and negative electrical charges -- a highly desired but often difficult-to-achieve combination in current efforts to create highly flexible electronic devices and other new-age technologies.
The research used a family of readily available and inexpensive hydrocarbons known as indenofluorenes to build molecular scaffolding for integrative circuitry. An indenofluorene-derivative framework, said co-author Michael Haley, head of the UO Department of Chemistry, offers more simplicity, flexibility and affordability than that available using many other hydrocarbon-based approaches.
Haley's lab in the UO's Materials Science Institute reported a linear version of the new molecular structure in the Journal of the American Chemical Society last June. For the new paper -- placed online in advance of regular publication in the ACS journal Organic Letters -- Haley's team manipulated that infrastructure into a more bent architecture and tested some of its fundamental optical and electronic properties.
Using organic molecules is helping materials scientists move beyond silicon semiconductor technology, said Aaron Fix, a doctoral student in Haley's lab and lead author of the new paper.
"You don't need to lay the molecules on silicon,” Fix said. “They can be laid on plastics and other materials, as long as you have the necessary metallic or graphite contacts. These new materials will allow for electronics that can take on stresses at levels traditional silicon, which is brittle, cannot handle. We will be able to make stretchable and bendable devices."
A lot of different materials can be used in organic electronic devices, Fix said. Most of them, he added, move positive charges well but not negative charges. "We are trying to fill that niche by developing materials that can do that well," he said.
Researchers pursuing devices utilizing organic semiconducting technology already are envisioning applications from roll-up computers to synthetic skin for robotic and prosthetic applications. Similar research done elsewhere with such approaches has surfaced in some smart phones and television screens.
"Specifically, we are doing research on transporting electrons using these indenofluorene materials for building integrated circuits for computers," said co-author Parker Deal, who worked in Haley's lab on both projects as an undergraduate chemistry major in the UO's Robert D. Clark Honors College. "This is fundamental research in that these are new molecules that nobody has made before, and we are studying them to see how effective they are and how they may further our improvement of these materials to build cheap, flexible devices."
The project, Haley said, is "old-school chemistry" and uses no precious metals. The hydrocarbons, he said, are cheap and easily manipulated for creating artificial materials.
"And we have shown that we are able to prepare the materials in gram quantities with good overall yields and excellent purity using methodologies that should work in large-scale production," he said.
Haley's team is about to work with an outside collaborator to test the new scaffolding in an electronic device. If successful, Haley said, work on the approach can move forward.
The National Science Foundation supported the research. Co-author Bradley Rose, a doctoral student, worked on both projects under the Emmanuil Troyansky Fellowship of the American Chemical Society.
Additional co-authors on the new paper were graduate student Chris Vonnegut and Lev Zakharov of the UO-based Center for Advanced Materials Characterization in Oregon (CAMCOR).
- by Jim Barlow, UO Office of Strategic Communications