Defect Passivation in CsPbBr ₃ Perovskite Using Phenethylammonium Bromide

Inorganic halide perovskites (HaP) such as CsPbBr 3 are promising materials for optoelectronic applications, but their performance is strongly affected by defect states, impurity phases, and limited crystallinity. In this work, we systematically investigate the combined effect of immersion time during a 2‐step solution deposition and subsequent surface passivation with phenethylammonium bromide (PEABr) on the structural, morphological, and optical properties of CsPbBr 3 HaP thin films. X‐ray diffraction reveals that 10 min immersion time yields the highest crystallinity (82.7%) with suppressed CsPb 2 Br 5 (Pb‐) and Cs 4 PbBr 6 (Cs‐rich) impurity phases, while PEABr passivation further reduces the dislocation density and microstrain without altering the intrinsic orthorhombic crystal structure CsPbBr 3 HaP. Scanning electron microscopy conforms that 20–40% PEABr treatment suppress pinholes and enhance film coverage, facilitating compact and smooth morphology synthesis. Optical study of CsPbBr 3 HaP thin film shows a direct broadgap of 2.33 eV with reduced Urbach energy for PEABr‐treated films, indicating suppressed disorder and trap states. Steady‐state photoluminescence intensities remarkably increased with PEABr concentration, demonstrating improved radiative recombination. This work highlights an integrated strategy where optimized immersion with moderate PEABr passivation yields defect‐suppressed CsPbBr 3 HaP thin films with superior optoelectronic quality, offering practical guidelines for stable inorganic perovskite solar cells.