At present, significant research efforts are being concentrated on enhancing the performance and stability of perovskite solar cells (PSC) by lowering defect traps. In this study, NH4+ and SCN- binary ions as additive were incorporated into perovskite precursor to control the crystal growth. Our best performance based on the devices fabricated under fully open air condition was improved from 15.67 to 18.75%, boosting by 20%. The stability results display that devices containing additive maintained similar to 90% of the initial efficiency for 400 h in ambient air with a humidity of 30%. We first study the fundamentals of defect properties and carrier recombination kinetics behind the multifaceted role of mixed NH4+ and SCN- ions. Compared to using a single active specie as additive, mixed-ions devices exhibit effective bifacial trap passivation as well as lowered defect density in not only perovskite bulk material but also interfaces significantly, leading to facilitated electron transport. Our work can manifest a simple ambient air based approach by the mixed binary ions as additives in order to potentially promote the commercial prospects of PSCs.