Bio-inspired coplanar-gate-coupled ITO-free oxide-based transistors employing natural nontoxic bio-polymer electrolyte

• Bio-inspired coplanar-gate-coupled indium-tin-oxide (ITO)-free oxide-based transistors are demonstrated by employing natural nontoxic bio-polymer electrolyte.
• Effective coplanar-gate coupling is realized due to the strong electric-double-layer effect in chitosan-based electrolyte dielectric.
• The device mechanism is proposed by using an equivalent circuit.

Bio-inspired coplanar-gate-coupled indium-tin-oxide (ITO)-free thin-film transistors (TFTs) are demonstrated by employing natural nontoxic bio-polymer electrolyte. Effective coplanar-gate coupling is realized through bottom-conducting fluorine-tin-oxide layer due to the strong electric-double-layer (EDL) effect in chitosan-based electrolyte dielectric. The optimized channel thickness (∼30 nm) gives the best performance with a low subthreshold swing of 0.22 V/dec, a high on-off ratio of 104, and a field-effect mobility of 3.53 cm2/V. Furthermore, the mechanism of coplanar multi-gate coupling in such TFTs is proposed by using an equivalent circuit composed of multiple paralleling EDL capacitors in series with an additional EDL capacitor. These results present a great step toward the potential applications for the next-generation green bio-compatible low-cost transparent coplanar-gate-integrated electronics.

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