The organic-inorganic perovskite solar cells (PSCs) have recently attracted significant attention owing to their remarkable photovoltaic performance. Herein, we fabricate a novel perovskite absorber Cs_0.05(FA_0.83MA_0.17)_0.95Pb_1−xZn_x(I_0.83Br_0.17)₃ by using ZnBr₂ as an additive. The introduction of zinc increases the grain size and reduces the grain boundary defects. At the optimized concentration of 0.5 mol% ZnBr₂ additive, the x-ray diffraction (XRD) shows the perfect crystallization of the perovskite film. The enhanced crystallization of the perovskite structure suppresses the non-radiative recombination loss and prolongs the carrier lifetime. The optimized PSC presents a champion power conversion efficiency (PCE) of 15.64 % and shows a negligible hysteresis effect. Moreover, the increased built-in electric field (V_bi) between the n-type Zn doped perovskite and the p-type CuSCN creates more driving force for the separation of photogenerated carriers and increases the open-circuit photovoltage (V_oc) of the device. The unencapsulated device maintains more than 87 % of its original PCE after aging for 90 days in the ambient condition, while the control device can only maintain 60 % of its original PCE. These results suggest that the simple B-site ion-doped perovskite could be a good option for the future improvement of PSCs.