We demonstrate the dipole-assisted carrier transport properties of bis(trifluoromethane)sulfonamide (TFSI)-treated O-ReS₂ field-effect transistors. Pristine ReS₂ was compared with defect-mediated ReS₂ to confirm whether the presence of defects on the interface enhances the interaction between O-ReS₂ and TFSI molecules. Prior to the experiment, density functional theory (DFT) calculation was performed, and the result indicated that the charge transfer between TFSI and O-ReS₂ is more sensitive to external electric fields than that between TFSI and pristine ReS₂. After TFSI treatment, the drain current of O-ReS₂ FET was significantly increased up to 1,113.4 times except in the range of -0.32-0.76 V owing to Schottky barrier modulation from dipole polarization of TFSI molecules, contrary to a significant degradation in device performance in pristine ReS₂ FET. Moreover, in the treated O-ReS₂ device, the dipole direction was highly influenced by the voltage sweep direction, generating a significant area of hysteresis in I-V and transfer characteristics, which was further verified by the surface potential result. Furthermore, the dipole state was enhanced according to the wavelength of the light source and photocurrent. These results indicate that TFSI-treated ReS₂ FET has large potential for use as next-generation memristor, memory, and photodetector.