Mixed Conduction in an N-Type Organic Semiconductor in the Absence of Hydrophilic Side-Chains

Jokubas Surgailis, Achilleas Savva, Victor Druet, Bryan D. Paulsen, Ruiheng Wu, Amer Hamidi-Sakr, David Ohayon, Georgios Nikiforidis, Xingxing Chen, Iain McCulloch, Jonathan Rivnay, Sahika Inal

Research output: Contribution to journalArticlepeer-review

80 Scopus citations


Organic electrochemical transistors (OECTs) are the building blocks of biosensors, neuromorphic devices, and complementary circuits. One rule in the materials design for OECTs is the inclusion of a hydrophilic component in the chemical structure to enable ion transport in the film. Here, it is shown that the ladder-type, side-chain free polymer poly(benzimidazobenzophenanthroline) (BBL) performs significantly better in OECTs than the donor–acceptor type copolymer bearing hydrophilic ethylene glycol side chains (P-90). A combination of electrochemical techniques reveals that BBL exhibits a more efficient ion-to-electron coupling and higher OECT mobility than P-90. In situ atomic force microscopy scans evidence that BBL, which swells negligibly in electrolytes, undergoes a drastic and permanent change in morphology upon electrochemical doping. In contrast, P-90 substantially swells when immersed in electrolytes and shows moderate morphology changes induced by dopant ions. Ex situ grazing incidence wide-angle X-ray scattering suggests that the particular packing of BBL crystallites is minimally affected after doping, in contrast to P-90. BBL's ability to show exceptional mixed transport is due to the crystallites’ connectivity, which resists water uptake. This side chain-free route for the design of mixed conductors could bring the n-type OECT performance closer to the bar set by their p-type counterparts.

Original languageEnglish (US)
Article number2010165
JournalAdvanced Functional Materials
Issue number21
StatePublished - May 21 2021
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General Chemistry
  • General Materials Science
  • Condensed Matter Physics


  • capacitance
  • in operando
  • n-type
  • organic electrochemical transistors
  • organic mixed conductors


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