Side gate vertical OECTs for integrated complementary circuits

Due to their unique mixed ionic-electronic working mechanism and good biocompatibility, organic electrochemical transistors (OECTs) show great potential for applications in bioelectronics and neuromorphic electronics. Compared with the widely adopted floating gate setup, side gate OECTs, with well-defined device geometry and simpler fabrication and testing procedures, which may unleash the potential of OECTs for further integration and commercialization, are still under development. Here, the gate size (S_G) and gate-channel distance (D_GC) of side gates in vertical OECTs are precisely modulated by combining high-resolution printed silver gates and photo-patternable transistor channels. It is demonstrated that the performances of Homo-gDPP-based vOECTs show distinct variation when S_G and D_GC vary from 200 to 1600 µm² and from 500 to 15 µm, respectively, for a channel area of only 30 × 30 µm². Champion on current, peak transconductance, and on/off current ratio values of 13.83 ± 0.54 mA, 87.56 ± 2.76 mS, and (5.21 ± 0.27) × 10⁸ are obtained with an S_G of 1600 µm² and a D_GC of 15 µm, which are among the highest reported for side gate OECTs. Moreover, high-density complementary circuits are integrated in combination with the channel size and S_G control, revealing the fastest switching speed (<9 ms) in reported side gate OECT circuits based on quasi-solid-state electrolytes (PEG-LiCl). This work provides a strategy for the optimal design and performance enhancement of OECTs and demonstrates ways for the miniaturization and integration of next-generation electronics based on OECTs.