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The organic electrochemical transistors (OECTs) are largely applied as bio‐ and ion‐sensor devices due to their performance in an aqueous environment with electrochemical doping/dedoping (reversible redox reactions) of the semiconducting layer through ion injection and also low (around 1 V) operation potentials. Aiming for the complementary circuits’ development and improvement of the sensors device, we report the application of spin coated polyaniline (PANI) in ambipolar OECT. The OECT operation is based on electrochemical protonation/deprotonation of PANI upon applied gate potential that was verified by cyclic voltammograms (CV) of PANI sample. The device operates in accumulation mode with on‐currents on the milliampere range due to the use of interdigitated array (IDA) microelectrodes architecture with a larger active area. Acid (HCl) doped PANI were applied in OECT device for comparison, and it presented improved performance with increasing drain‐source current up to 38%, reaching 4.8 mA for the n‐type device. This current increase is due to the narrower bandgap of doped PANI that affects the injection barrier. The HCl doped PANI was evaluated by UV‐Vis spectrophotometry and CV analysis. Using deionized water as electrolyte defunctionalized the PANI‐based OECT (no current modulation observed) because the absence of ions in the electrolyte interrupts the electrochemical doping. This is the opposite for the poly(3‐hexylthiophene) (P3HT)‐based electrolyte‐gated organic field‐effect transistor (EGOFET) due to the polymeric hydrophobicity nature that allows for field‐effect modulation in the electrolyte/semiconductor interface. The results presented may open new possibilities for bio‐ and ion‐sensors devices.

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