Ionic-Electronic Coupled Polymer Semiconductor with Efficient Ion Transport and High Scalability for Neuromorphic Applications

Recently, efforts to overcome the limitations of high energy consumption because of the enhanced performance of electronic devices have emerged, with neuromorphic electronics based on parallel processing attracting attention as a new paradigm. Organic electrochemical transistors (OECTs) are promising candidates for neuromorphic electronics due to their ability to realize ion-to-electron transduction with low power consumption. Ion-to-electron transduction enables the implementation of ion-driven biological synaptic functions in OECTs. Since this transducing ability is determined by ionic currents in polymer semiconductor (PS), enhancing the flow of ionic circuits has been a major challenge. To address this, ion-compatible PS based on molecular tailoring methods such as side chain engineering has been intensively developed; however, limited scalability makes it difficult to apply them to practical neuromorphic devices.<br/>In this study, to improve ion transport and scalability simultaneously in OECTs, we demonstrate ionic-electronic coupled PS (ICPS) utilizing ethylene oxide (EO)-integrated photo-crosslinkers. The formation of ICPS network occurs by reacting nitrene (-N) groups of the crosslinkers activated under UV light, with alkyl side chains of PS. This methodology provides an accelerating effect of ion transport via EO without affecting the crystalline structure of the PS. On the basis of this, the ICPS achieved signal amplification of ionic currents as the length of the EO moieties increased, implying that the ion transport properties of the ICPS are strongly affected by the EO moieties. The incorporation of EO also creates an environment in which interactions with anions are stabilized, forming pathways that enhance ion mobility, thereby improving the penetration and diffuse out rates of ions (&lt;50 ms). Furthermore, as a result of the superior chemical endurance of ICPS, high-resolution patterning (&lt;10 um) was implemented through direct photolithography that simplifies the process compared to photoresist-based lithography. Consequently, the ICPS not only facilitates ion transport without degradation of electronic performance but also successfully secures high-density patterns. This demonstrates that our material design strategy for the ICPS can provide a new direction for the development of scalable, ion-compatible PS for integrated neuromorphic disciplines.