We fabricated high-quality CsPbBr3 perovskite nanonet films with the assistance of polystyrene spheres, and constructed self-powered photodetectors (PDs) with an ITO/SnO2/CsPbBr3/carbon structure. By passivating the nanonet with different concentrations of 1-butyl-3-methylimidazolium bromide (BMIMBr) ionic liquid, we found that as the concentration of BMIMBr increases, the dark current of the device first decreases and then gradually increases, while the photocurrent remains essentially unchanged. Finally, the PD with 1 mg mL-1 BMIMBr ionic liquid exhibited the best performance with a switch ratio of about 1.35 × 106, a linear dynamic range extending to 140 dB, and responsivity and detectivity values of 0.19 A W-1 and 4.31 × 1012 Jones, respectively. These results provide an important reference for fabricating perovskite PDs.