McNeill Research Group

Donor–Acceptor Conjugated Polyelectrolytes for Organic Electrochemical Transistors: Interplay between Main-Chain Charge Carriers and Side-Chain Ions Poly(diketopyrrolopyrrole) (PDPP)-based π-conjugated polyelectrolytes (CPEs), facilitating either electron or hole transport for applications in organic electrochemical transistors (OECTs), were synthesized. By equipping each polymer main-chain with neutral, anionic, or cationic side chains, the resulting series of polymers encompasses all possible combinations of negative, positive, and neutral side-chain ionic charges in combination with in situ-generated holes or electrons on the backbone. This investigation focuses on uncovering intramolecular synergies and antagonisms of the mixed conductors (ions and electrons), with a special emphasis on parameters relevant to both p- and n-type OECT devices using CPEs. While UV–vis absorption spectroscopy suggests only small changes in the optoelectronic properties among the differently charged polymers, in situ and operando GIWAXS analyses revealed significant differences in swelling behavior. We observed that cationic and anionic side chains induce distinct alterations in interlamellar spacing with varying degrees of swelling influenced by electrochemical doping and ion diffusion, which is controlled by the sign of the applied potential. Anionic side chains favor hole transport and enable an earlier oxidation onset of the donor CPE, as demonstrated in the OECT and spectroelectrochemistry (SEC) studies. Such changes are crucial for improving the p-type OECT efficiency and responsiveness. The opposite effect is observed in cationic polyelectrolyte hole conductors. Conversely, electron-transporting materials benefit from cationic side chains, while anionic side chains prove detrimental for n-type device operation. These results suggest a general design strategy for anionic or cationic donor and acceptor materials for the exploitation of OECT applications, where the formation and transport of charge carriers formed in operando (electrons or holes) are favored by the opposite side-chain ions immobilized in a CPE chain, resulting in high drain current at low gate voltages, improved transconductance, and low redox onset voltage.

🚨 Publication alert! 🚨
How do the ionic charges on the side chains of π‑conjugated polyelectrolytes determine performance in organic electrochemical transistors? Find out in this paper from Andreas Erhardt, graduate of our OPTEXC IRTG with @unibayreuth.bsky.social.
pubs.acs.org/doi/abs/10.1...

Job Search

I have a post-doc opening (link below) and a fully-funded PhD position available (physics or materials background) on the topic of cryo-electron microscopy of organic semiconductors. Potential PhD students email me your CV and why you think you are suitable.
careers.pageuppeople.com/513/cw/en/jo...

Multiple PhD scholarship positions avaiable for research into next generation semiconductors as part of the "OPTEXC" International Research Training Group with the University of Bayreuth in Germany.

careers.pageuppeople.com/513/cw/en/jo...

Last year: C, not shortlisted. This year: B, shortlisted. Main change was to redirect to a different panel (from EIC to MPCE). Also tried to jazz it up a little compared to last year.