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Various internal and external defects present in the perovskite film are one of the main factors that cause low efficiency and stability, and in order to realize high-performance perovskite solar cells, it is necessary to develop a method to effectively suppress them. In this study, a heterofunctional dopants strategy was attempted to integrate the effect of alkali metal cations (Rb+ and K+) and formate anion (HCOO¯) through doping engineering with alkali-metal formates, i.e., rubidium formate (RbHCOO) and potassium formate (KHCOO). Inclusive physical and photoelectric analysis revealed that doping with a small amount of alkali-metal formate leads to crystal growth and reduction of grain boundaries, and further passivates or inhibits bulk and surface defects. As a result, the photogenerated charge recombination was reduced and the charge carrier transport was improved, leading to improved PSC performance. RbHCOO-doped inverted planar PSCs achieved a PCE of up to 20.41% with long-term stability. Our findings provide a way for producing high-quality perovskite films with low defect densities that are essential for realizing high-performance PSCs.