## 2 Materials and Methods  
The sample fabrication and characterization were carried out in a cleanroom environment. The OETCs involved in this work were a side-gated planar electrode configuration utilizing a three-stage photolithography patterning process (see Figure 1a). A glass substrate (1\({}^{\prime\prime}\)\(\times\) 1\({}^{\prime\prime}\), 3 nm Cr and 50 nm Au) was spin-coated (60 s, 3000 rpm; Sawatec SM-180-BT, Sax, Switzerland ) with the photoresist AZ 1518 (MicroChemicals GmbH, Ulm, Germany) followed by baking on a hotplate (60 s, 110 \({}^{\circ}\)C; Sawatec HP-150, Sax, Switzerland). The illumination of the electrode pattern ensued in a mask aligner (10 s, I-line 365 nm, 167 W; SUSS Microtec AG, Garching, Germany). The development of AZ 1518 (60 s, AZ 726 MIF; MicroChemicals GmbH, Ulm, Germany) and etching of Au (60 s; 10% diluted aqueous; Merck KGaA, Darmstadt, Germany) and Cr (20 s, 10% diluted aqueous; Merck KGaA,Darmstadt, Germany), respectively, produced the desired electrode pattern on the glass substrate. The second stage of photolithography started with the deposition of PEDOT:Tos. We followed a five-step base-inhibited VPP process [22] with some modifications. First, the substrate was spin-coated (15 s, 1500 rpm) with the reactants Fe(III):Tos (324 mg; Sigma Aldrich, Taufkirchen Germany), pyridine (32 uL; Alfa Aesar, Karlsruhe, Germany), and butanol (1.6 mL;Acros Organics, Karlsruhe, Germany), followed by air drying for 30 min. The polymerization was carried out in a desiccation chamber (Gebr. Rettberg GmbH, Gottingen, Germany). A Petri dish containing EDOT (Sigma Aldrich, Taufkirchen Germany) was kept at the bottom of the desiccation chamber, while the substrate containing the reactants was set on a stage. The desiccation chamber was kept on a hotplate at 70 \({}^{\circ}\)C, which maintained the substrate temperature at around 50 \({}^{\circ}\)C (VOLTCRAFT IR 500-12S, Hirschau, Germany). The desiccation chamber was connected to a vacuum pump rated at 780 Pa. The equilibration time was 10 min, and the polymerization time was 1 h. The post-polymerization thermal annealing was carried out for 0, 1, and 4 h on a hotplate at 70 \({}^{\circ}\)C. Finally, the deposited PEDOT:Tos was carefully dipped in ethanol to remove any residuals. Next, the substrate with the electrode pattern and the deposited polymer was spin-coated with an SL1 sacrificial layer (60 s, 3000 rpm; post-baking at 100 \({}^{\circ}\)C for 60 s; Orthogonal Inc., Rochester, NY, USA) [21] and photoresist AZ nLOF 2020 (60 s, 3000 rpm; post-baking at 110 \({}^{\circ}\)C for 60 s; MicroChemicals GmbH, Ulm, Germany). The illumination in the mask aligner (14 s, I-line 365 nm, 167 W; SDSS Microtec AG, Garching, Germany) and post-baking followed (60 s, 110 \({}^{\circ}\)C). The resist was developed by AZ 726 MIF (60 s; MicroChemicals GmbH, Ulm, Germany), and the unprotected sacrificial layer was removed by spin coating (3000 rpm, increments of 15 s until undercut appeared) with HFE (3M Performance Chemicals, Nordrhein-Westfalen Germany). The final PEDOT:Tos pattern on the gate and channel was obtained by dry etching with oxygen plasma (300 s, 100 V bias, 50 W RF power, 30 Pa; Aurion VPA-14-01, Seligenstadt, Germany). The crosslinked resist and underlying SL1 were removed by keeping the substrate in the OSCoR Developer 103a (Orthogonal Inc.) overnight. The SE pattern was achieved by the same method reported earlier [19]. The thickness measurements were taken using a profilometer (Veeco Dektak 150, Aschheim, Germany). All electrical and impedance measurements were carried in a N\({}_{2}\) glovebox (MBraun, Garching Germany). The electrical measurements were taken with two Keithley 236 SMUs (Oregon, United States) coupled with the software SweepMe! (Dresden, Germany). The impedance measurements were taken with Metrohm Autolab PGSTAT302N (Filderstadt, Germany) in the potentiostatic mode with an RMS amplitude of 10 mV and without any DC offset.