In this study, the electrochemical polymerization of 9-carbazole acetic acid (CzA) monomer was synthesized in various feed ratios of room-temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) in acetonitrile (ACN) to investigate the effect of RTIL on morphology, impedance, capacitance, and semiconducting properties. It was observed that the low amounts of the RTIL (10 and 20%) in the mixture improve the electrochemical polymerization process compared to the RTIL-free electrolyte. Indeed, after a certain amount% BMIMBF4 which was threshold (40%), the process turned strongly unfavored. Scanning electron microscopy (SEM) was used to understand the influence of the feed ratio of BMIMBF4 to ACN on the surface structure of obtained polymer films. The surface morphology of PCzA revealed dependence on the feed ratio of BMIMBF4. Electrochemical impedance spectroscopic (EIS) experiments were performed in a pure BMIMBF4 (100%) indicated that as the feed ratio of BMIMBF4 increased, the capacitive behavior of the polymer decreased. From the Mott-Schottky analysis, the highest flatband potential (E-FB = 2.87 V) was obtained for the 40% PCzA-BMIMBF4 film. (C) 2016 The Electrochemical Society. All rights reserved.