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The efficient production of uniform, high-quality transport layers beneath the light-absorbing layer is crucial for the performance and scalability of perovskite solar cells (PSCs). This study investigates the incorporation of potassium fluoride (KF) into tin dioxide (SnO2) nanoparticle solutions to enhance the properties of the electron transport layer (ETL) in PSCs. By introducing KF, we observed a significant reduction in SnO2 particle size and improved zeta potential, resulting in a more uniform ETL. Experimental analysis demonstrated that optimal KF concentrations in SnO₂ nanoparticles improved coverage and uniformity on substrates, as confirmed by surface SEM and AFM measurement. Such improvement in ETL morphology reduced charge recombination and increased charge carrier mobility of PSCs. Specifically, PSCs with 0.02 M of KF addition showed increased power conversion efficiencies (PCE), up to 24.3%. Furthermore, large-area PSC modules with a 25 cm2 aperture area exhibited an average PCE enhancement up to 18.0% due to superior ETL uniformity. Additionally, KF addition also aided the stability enhancement, maintaining 90% of their initial efficiency after 250 hours under 60 ± 5% relative humidity. Our findings underscore the importance of ETL uniformity and provide insights into the role of KF doping in advancing PSC performance, paving the way for more efficient and scalable solar energy solutions.