Naphthalene diimide-based n-type small molecule organic mixed conductors for accumulation mode organic electrochemical transistors

Organic mixed ionic-electronic conductors (OMIECs), which transport both ionic and electronic charges, development are important for progressing bioelectronic and energy storage devices. The p-type OMIECs are extensively investigated and used in various applications, whereas the n-type ones lag far behind due to their moisture and air instability. Here, we report the synthesis of the novel n-type naphthalene diimide (NDI)-based small-molecule OMIECs for organic electrochemical transistors (OECTs). The electro-active NDI molecule with the linear ethylene glycol side chains is a promising candidate for n-type channel material to obtain accumulation mode OECTs. This NDI-based small-molecule OMIEC, gNDI-Br-2, demonstrates ion permeability due to the attachment of the glycol side chains with optimized ionic-electronic conductions. OECT devices with gNDI-Br-2 channel material displays excellent performance in water and ambient stability. OECTs fabricated with two different concentrations, 50 mg mL(-1) and 100 mg mL(-1) of gNDI-Br-2 demonstrate a transconductance value of 344 +/- 19.7 mu S and 814 +/- 124.2 mu S with the mobility capacitance product (mu C*) of 0.13 +/- 0.03 F cm(-1) V-1 s(-1) and 0.23 +/- 0.04 F cm(-1) V-1 s(-1), respectively. These results demonstrate the n-type OMIEC behaviour of the NDI-based small-molecule and its applicability as an OECT channel material.