Benefiting　from　the　simple　and　low-cost　fabrication　of　the　one-step　anti-solvent　spin-coating　process,　the　perovskite　solar　cells　(PSCs)　have　a　boost　development.　However,　a　great　number　of　defects　are　generated　during　solution-fabrication　process,　retarding　the　development　of　PSCs　seriously.　In　this　study,　the　utilization　of　4,5dicyanoimidazole　(DCI)　as　an　additive　for　perovskite　precursor　solution　was　investigated.　The　presence　of　the　double　-CN　groups　in　DCI　facilitated　the　formation　of　Lewis　acid-base　coordination　with　unsaturated　Pb2+　ions,　as　well　as　interaction　with　I-　anions　by　the　-NH-　moiety,　resulting　in　the　enhanced　perovskite　film　crystallinity,　the　reduced　grain　boundaries,　and　a　significant　reduction　in　the　defects　density　of　the　perovskite　film.　The　decreased　trap-assisted　recombination　and　voltage　open　circuit　(VOC)　losses　in　the　PSC　resulted　in　the　improved　photovoltaic　performance　of　device　treated　by　DCI　molecule,　the　PCE　increased　from　19.59　%　to　21.87　%　significantly.　Moreover,　the　unencapsulated　device　with　DCI　additive　exhibited　a　remarkable　87.8　%　retention　of　its　initial　PCE　after　exposure　under　10-20　%　relative　humidity　for　60　days,　demonstrating　an　excellent　stability　than　control　device.