In past years, halide perovskite solar cells (PSCs) have attracted much attention and are considered as the next-generation solar cells due to their excellent performance. Compared to the conventional structure, the inverted perovskite solar cell device has great potential in large-scale practical applications due to the low-temperature manufacturing process. However, the power conversion efficiency (PCE) is still lower than conventional structure devices, which is because of the high trap density in the surface and grain boundary of perovskite film. One kind of defect is the iodine vacancy caused by methylammonium iodide (MAI) volatilization during perovskite film annealing. I^- could be oxidized into I₂ and then volatilize out during the perovskite film annealing, the vacancy of I^- could form trap states in the surface and grain boundary of the perovskite film. The surface traps induce many defects and increase the charge recombination rate in the inverted polycrystalline perovskite film, which causes PCE loss in the devices. Although lots of efforts are to improve the PCE of devices, perovskite solar cell device is still hard to practical applicate due to poor stability under light exposure conditions. Under light soaking especially UV light, perovskite film would degrade which means I₃^- easily change to I₂ and induce the lattice defects of perovskite film, which further influence the performance of PSCs. Herein, we present a strategy to suppress the I₂ generation to decrease the trap density, reduce the charge recombination in perovskite film and further improve the performance of devices by an ammonium salt named tetrabutylammonium chloride (TBACl) modified. The PCE of devices increase from 18.52% to 20.36% after TBACl was modified, and TBACl also reduce the Voc loss in the perovskite solar cell devices. Furthermore, TBACl passivation enhances the light stability of devices and slows down PSCs degradation with UV light soaking. Because TBACl distributes in the surface and GBs of perovskite film that could absorb the UV light and decrease the effects on the perovskite layer. Benefiting from the influence of TBACl on perovskite solar cell devices, the devices could maintain over 90% with light soaking 120 h and UV light irradiation 450 min, respectively. However, the control devices only could maintain ~47% and ~51% of the initial PCE values under light exposure and UV light soaking conditions, respectively. Thus, we provide a low-cost, easy, and effective post-treatment strategy to enhance the device performance and improve the light stability of perovskite solar cell devices.