Enhancing the Performance of N-Type Organic Mixed Conductors by Blending Polymers with Alkyl and Oligoglycol Side Chains

Conjugated polymer organic mixed ionic electronic conductors (OMIECs) are promising materials for bioelectronics, neuromorphic computing, and energy storage. Compared to their p-type counterparts, n-type are typically not as stable and have significantly lower figures of merit. Naphthalene diimide (NDI) based n-type OMIEC copolymers with hydrophobic alkyl and hydrophilic oligoglycol side chains show stability in water. In this work, we investigate the performance of blends of p(gNDI-gT2) and N2200. We employ nanoscale infrared imaging with photoinduced force microscopy (PiFM) to interrogate how p(gNDI-gT2) and N2200 phase separate at the nanoscale. We also use a combination of grazing incidence wide-angle X-ray scattering (GIWAXS) and UV-vis spectroelectrochemistry to monitor polaron formation and ion movement in these blended films. To determine whether the polymer blends boost organic electrochemical transistor (OECT) performance, we fabricate OECTs with active layers consisting of different ratios of p(gNDI-T2) and N2200. We find enhanced OECT performance when we add small amounts of N2200 to p(gNDI-T2). Overall, this study emphasizes that blending two n-type materials can result in enhanced device performance.