Charge Carrier Mobility in Organic Mixed Ionic-Electronic Conductors by the Electrolyte-Gated van der Pauw Method

Organic mixed ionic-electronic conductors (OMIECs) combine electronic semiconductor functionality with ionic conductivity, biocompatibility, and electrochemical stability in water and are currently investigated as the active material in devices for bioelectronics, neuromorphic computing, as well as energy conversion and storage. Operation speed of such devices depends on fast electronic transport in OMIECs. However, due to contact resistance problems, reliable measurements of electronic mobility are difficult to achieve in this class of materials. To address the problem, the electrolyte-gated van der Pauw (EgVDP) method is introduced for the simple and accurate determination of the electrical characteristics of OMIEC thin films, independent of contact effects. The technique is applied to the most widespread OMIEC blend, poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonic acid) (PEDOT:PSS). By comparing with organic electrochemical transistor (OECT) measurements, it is found that gate voltage dependent contact resistance effects lead to systematic errors in OECT based transport characterization. These observations confirm that a contact-independent technique is crucial for the proper characterization of OMIECs, and the EgVDP method reveals to be a simple, elegant, but effective technique for this scope.

Automated summary

Organic mixed ionic-electronic conductors (OMIECs) are versatile materials investigated for use in bioelectronics, neuromorphic computing, and energy devices. The electrolyte-gated van der Pauw (EgVDP) method has been introduced to accurately determine the electrical characteristics of OMIEC thin films, independent of contact effects, highlighting the importance of a contact-independent technique for precise characterization of these materials.