Organic-inorganic hybrid perovskites (OIHP) have attracted a great deal of attention as promising light-emitting materials, because of their low-cost production via simple solution processing, high color purity, and easily tunable bandgaps. Nevertheless, the fabrication of OIHP films for light-emitting diodes generally requires complicated post-treatments, such as an anti-solvent dripping process, owing to the poor film forming property of the perovskite precursor solution. In this work, we employed an ionic liquid, methylammonium acetate (MAAc), as an additive to optimize the growth of FAPbBr3 perovskite films via an anti-solvent-free approach. The influence of MAAc on the crystallization kinetics of FAPbBr3 phase and optoelectronic properties of the resulting perovskite films have been systematically investigated. Our results demonstrate that MAAc is an effective modifier for creating perovskite films with reduced grain size, homogeneous grain distribution, and smooth surface, leading to an enhanced average lifetime of the excitons. Perovskite light-emitting diodes (PeLEDs) containing FAPbBr3 films obtained via incorporating 10 vol% MAAc as an additive exhibited considerably suppressed leakage current, and a significant enhancement in current efficiency (CE) from 0.027 to 4.85 cd A-1. These findings reveal that the incorporation of a suitable additive could play a beneficial role in the formation of well-optimized perovskite films, which would ultimately lead to the realization of PeLEDs with improved performance.