In Operando Characterization Elucidates Cation-Backbone Interactions in n-type Ladder OMIECs

Tom van der Pol^a, Han-Yan Wu^a, Demetra Tsokkou^b, Vincent Lemaur^c, Chiara Musumeci^a, Chi-Yuan Yang^a^,^d, Natalie Banerji^b, David Beljonne^c, Simone Fabiano^a^,^d

^aLaboratory of Organic Electronics, Linköping University, 60174 Norrköping, Sweden

^bDepartment of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.

^cLaboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, 7000 Mons, Belgium.

^dn-Ink AB, Teknikringen 7, 583 30 Linköping, Sweden

Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS Fall 2024 Conference (MATSUSFall24)

#OMIEC - Understanding Mixed Ionic-Electronic Conductors

Lausanne, Switzerland, 2024 November 12th - 15th

Organizers: Natalie Banerji and Olivier Bardagot

Invited Speaker, Tom van der Pol, presentation 098
DOI: https://doi.org/10.29363/nanoge.matsusfall.2024.098
Publication date: 28th August 2024

Organic mixed ion-electron conducting materials (OMIECs) find use in several exciting applications due to their ability to transduce ionic and electronic signals. Some recent work has leveraged an anti-ambipolar behavior, whereby extensive electrochemical doping lowers the conductivity rather than increasing it further. The underlying mechanisms governing this phenomenon are unknown but highly significant for further device exploration and optimization. Device-relevant material characterization is not straightforward, however, since OMIECs operate in a complex environment including an electrolyte containing positively and negatively charged ions. Given their nature of mixed conductivity, OMIECs are expected to show strongly different material characteristics ex-situ, which markedly calls for in-operando characterization.

Here, we apply several in-operando characterization techniques to state-of-the-art n-type ladder-type OMIECs and uncover previously undetected ion-backbone interactions. Through in-operando infra-red (IR) spectroscopy we find these ion-backbone interactions are crucially important to explain OECT and anti-ambipolar characteristics. Furthermore, we find that the same cation-backbone interactions instigate changes in the film morphology, whereby the choice of electrolyte dictates the nature of the changes.

Our results provide insight into the electrochemical doping mechanism of these polymers and uncover structure-property relations governing their device functions. These insights enable targeted optimization of both polymer structure and employed electrolyte, as well as provide instruments for possible new applications.

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