Constructing　2D/3D　perovskite　heterostructures　with　organic　molecules　is　key　to　improving　the　power　conversion　efficiency　(PCE)　and　stability　of　perovskite　solar　cells　(PSCs).　However,　a　comprehensive　understanding　of　the　inhibitory　relationship　between　the　2D　perovskite　layer　and　ion　migration　at　the　interface　is　still　lacking.　In　this　study,　we　use　different　alkyl　ammonium　iodides　to　build　2D/3D　perovskite　heterostructures.　The　research　results　show　that　both　the　chain　length　of　alkyl　and　amino　group　count　in　alkyl　ammonium　iodide　can　significantly　affect　the　crystal　structure　orientation　of　the　2D　perovskite　layer.　A　Dion-Jacobson　(DJ)　2D/3D　structure　treated　with　ODADI　shows　superior　defect　passivation　and　carrier　extraction,　leading　to　PSCs　with　a　24.51　%　PCE.　Furthermore,　the　perovskite　based　on　ODA　cations　eliminates　the　influence　of　Van　der　Waals　interaction　in　perovskite　based　on　BA　or　OA　cations,　which　improves　the　stability　of　the　lattice　structure,　and　significantly　inhibits　ion　migration.　Therefore,　after　a　maximum　power　point　stability　test　of　1500　h,　devices　retain　approximately　88　%　of　their　initial　PCE.　This　work　offers　fresh　insights　into　optimizing　interfaces　in　2D/3D　PSCs　by　selecting　suitable　organic　molecules.