Funded by the Air Force Office of Scientific Research and published in PNAS, Purdue Researchers have discovered a fundamentally new way of charge transport in organic carbon-based materials. 

Plastic electronic materials are heavily studied for their many end-use optical, electronic and spintronic applications. In most contemporary organic electronic materials, doublet cations or anions serve as the charge carrier. However, radical polymers, such as nonconjugated macromolecules bearing open-shell entities, are a developing class of conductors that show promise by offering unique transport properties for both electronic and spintronic uses. 

The team of researchers from the Davidson School of Chemical Engineering, consists of Graduate Research Assistant Siddhartha Akkiraju, Ph.D Candidate Dylan Gilley, Charles Davidson Associate Professor Brett Savoie and R. Norris and Eleanor Shreve Professor Bryan Boudouris. Together, they used a combination of experimental and computational measurements to demonstrate that unlike their common doublet cation and anion conducting polymer counterparts, the charge in radical polymers are singlet cations. Singlet cations are distinctly different from the charge carriers in classic organic electronic materials systems and importantly, present several macroscopic experimental observables that detail their fundamental molecular principles.

Two major observations emerged from the current study. According to Savoie, “the first is the confirmation of singlet charge carriers by the observation of weak magnetoresistive effects. This is the first direct evidence of what is otherwise a foundational assumption for radical polymers.” But he also points out that the study raised new question. “The second finding is that although the magnetoresistance is weak, it is persistent and non-negligible, which poses a bit of a mystery about its origins, whether it can be controlled, or even exploited in some way.” 

"Since the Nobel Prize-winning discovery that plastics can conduct charge, research and applied work have focused on establishing the molecular-level principles that allow for this technology that enables products such as mobile phone and television displays. By elucidating a new means of transport in an emerging class of polymers, we are positioned to take key steps forward in materials for advanced computing and quantum information systems.”