This study reports the synthesis and characterization of phase-pure α-FAPbI3 perovskite films at room temperature with in-situ grain-boundary passivation. The perovskite films were prepared by spin-coating a solution containing FAI, PbI2, MACl, MDACl2, and TFAI. The films were then annealed at 150°C for 15 minutes to achieve complete crystallization. The films were characterized using various techniques including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), grazing-incident wide-angle X-ray scattering (GIWAXS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS), ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), and conductive atomic force microscopy (C-AFM). The results showed that the addition of TFAI improved the crystallinity and reduced the grain boundary defects in the perovskite films. The films exhibited high crystallinity, with grain sizes ranging from 1 to 5 µm. The GIWAXS analysis confirmed the formation of the α-phase of FAPbI3. The XRD analysis showed that the perovskite films had a cubic structure. The FTIR analysis confirmed the presence of the perovskite structure. The ToF-SIMS analysis showed that the films had a uniform composition. The UPS and XPS analyses confirmed the chemical composition of the films. The C-AFM analysis showed that the films had a uniform surface morphology. The absorption spectra of the films showed a strong absorption in the visible range. The steady-state PL spectra showed a strong emission in the visible range. The PL mapping of the films showed a uniform emission. The J-V measurements showed that the films had high power conversion efficiency (PCE). The external quantum efficiency (EQE) measurements showed that the films had high EQE. The Mott-Schottky plots showed that the films had a high built-in potential. The SCLC calculations showed that the films had a high trap density. The results indicate that the addition of TFAI significantly improves the quality of the perovskite films, leading to high performance in solar cells.This study reports the synthesis and characterization of phase-pure α-FAPbI3 perovskite films at room temperature with in-situ grain-boundary passivation. The perovskite films were prepared by spin-coating a solution containing FAI, PbI2, MACl, MDACl2, and TFAI. The films were then annealed at 150°C for 15 minutes to achieve complete crystallization. The films were characterized using various techniques including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), grazing-incident wide-angle X-ray scattering (GIWAXS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS), ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), and conductive atomic force microscopy (C-AFM). The results showed that the addition of TFAI improved the crystallinity and reduced the grain boundary defects in the perovskite films. The films exhibited high crystallinity, with grain sizes ranging from 1 to 5 µm. The GIWAXS analysis confirmed the formation of the α-phase of FAPbI3. The XRD analysis showed that the perovskite films had a cubic structure. The FTIR analysis confirmed the presence of the perovskite structure. The ToF-SIMS analysis showed that the films had a uniform composition. The UPS and XPS analyses confirmed the chemical composition of the films. The C-AFM analysis showed that the films had a uniform surface morphology. The absorption spectra of the films showed a strong absorption in the visible range. The steady-state PL spectra showed a strong emission in the visible range. The PL mapping of the films showed a uniform emission. The J-V measurements showed that the films had high power conversion efficiency (PCE). The external quantum efficiency (EQE) measurements showed that the films had high EQE. The Mott-Schottky plots showed that the films had a high built-in potential. The SCLC calculations showed that the films had a high trap density. The results indicate that the addition of TFAI significantly improves the quality of the perovskite films, leading to high performance in solar cells.