In this study, the photovoltaic properties of Cu₂SnS₃ (CTS) solar cells were evaluated by varying the amount of potassium fluoride (KF) added to the films. KF deposition was used to improve the photovoltaic properties of the CTS solar cells as compared with alkali metal-free films. The best photovoltaic properties were obtained for the thin film in which 40 mg of KF was evaporated.