Utilizing PEDOT as an Electrode and Ion-Conducting Layer in BBL-Based Vertical OECTs

Organic mixed ion-electron conductors (OMIECs), especially poly(3,4-ethylenedioxythiophene) (PEDOT), are widely studied in organic electrochemical transistors (OECTs) as channel materials because of their ability to simultaneously transport ions and electrons; however, applications beyond channel materials are still unexplored. In this study, we explore the dual functionality of PEDOT as both an electrode and an ion-conducting layer in vertical OECTs (vOECTs). The channel, made of poly(benzimidazobenzophenanthroline) (BBL), is sandwiched between a top PEDOT layer and a bottom gold electrode; the configuration allows for the large dimensions of our devices, leading to high transconductance without sacrificing response time, and indicates that our process can also be integrated with printing methods. A detailed analysis of the device characteristics reveals the vertical mobility of BBL, providing valuable insights into its charge transport mechanisms. Furthermore, we elucidate the threshold voltage ( V th ) shift induced by the PEDOT layer, attributing it to the difference in the highest occupied molecular orbital levels compared to the gold electrode. Our findings highlight the potential of PEDOT as a multifunctional OMIEC, particularly contributing to advancements in printed OECT applications.