Organic electrolyte gated transistors (OEGTs) have great attention as the fundamental building units for high-performance (bio-)electronic devices/circuits because of their outstanding characteristics, such as operating at low voltage and high transconductance. However, OEGTs based on p-type polymer semiconductors are advanced, n-type polymer semiconductors continue to face challenges with low performance. Thus, this performance mismatch hinders the development of all flexible OEGT-based logic circuits.
In this research, we devolped BBL-based OEGTs using nonvolatile, highcapacitance ionogel, which are composed of ionic liquid (IL) swelling in 3D polymer networks. Resulting devices exhibited high on/off current ratios (~105) and high transconductance (4.6 S·cm-1).
These outstanding BBL-based EGT characteristics were only observed after the first operating cycle. To investigate the cause of this phenomenon, additional experiments were conducted by changing the operating conditions (scan rate, scan range) of the OEGTs. As a result, this phenomenon occurred when a sufficient number of ions penetrated into the BBL film. Furthermore, we investigated the impact of electrochemical ion doping on the morphology of BBL using Grazing-incidence wide-angle X-ray scattering (GIWAXS). This measurement shows that electrochemical doping process with bulk ions of ILs induces irreversible morphological variations of the polymer film, which served as ion pathways, facilitating rapid ion transport.
Furthermore, due to the non-volatile characteristic of the ionogels, OEGTs retained their device performance even after undergoing high temperature annealing (up to 100 ℃) and showed long-term operation (> 4000 s) under ambient conditions. Furthermore, we fabricated flexible and all organic complementary logic circuits by connecting p- and n-type OEGTs. This study will offer insights for the comprehension of operating mechanisms and device optimization when utilizing ionic liquids as electrolytes in n-type OEGTs.