The　surface,　interfaces　and　grain　boundaries　of　a　halide　perovskite　film　carry　critical　tasks　in　achieving　as　well　as　maintaining　high　solar　cell　performance　due　to　the　inherently　defective　nature　across　their　regime.　Passivating　materials　and　felicitous　process　engineering　approaches　have　significant　ramifications　in　the　resultant　perovskite　film,　and　the　solar　cell＇s　overall　macroscale　properties　as　they　dictate　structural　and　optoelectronic　properties.　Herein,　we　exploit　a　vast　number　of　defect　engineering　approaches　aiming　to　increase　the　performance　and　the　stability　of　perovskite　solar　cells,　especially　against　humidity,　continuous　illumination,　and　heat.　This　review　begins　with　the　perovskite　materials＇　fundamental　structural　properties　followed　by　the　advances　made　to　induce　higher　stabilization　in　perovskite　solar　cells　by　fine-tuning　materials　chemistry　design　parameters.　We　continue　by　summarizing　defect　passivation　strategies　based　on　molecular　entities＇　application,　including　suitable　functional　groups　that　enable　sufficient　surface,　bulk　and　grain　boundary　passivation,　morphology,　and　crystallinity　control.　We　also　present　methods　to　control　the　density　of　defects　through　the　variation　of　processing　conditions,　solvent　annealing　and　solvent　engineering　approaches,　gas-assisted　deposition　methods,　and　use　of　self-assembled　monolayers,　as　well　as　colloidal　engineering　and　coordination　surface　chemistry.　Finally,　we　give　our　perspective　on　how　a　combined　understanding　of　materials　chemistry　aspects　and　passivation　mechanisms　will　further　develop　high-efficiency　and　stability　perovskite　solar　cells.　©　2021　The　Royal　Society　of　Chemistry.