Metal　halide　perovskites　have　been　extensively　studied　due　to　their　exceptional　optoelectronic　properties.　However,　the　fabrication　of　perovskite　solar　cells　(PSCs)　has　been　hindered　by　the　poor　stability　and　high　costs　of　hole　transport　layers　(HTLs)　such　as　Spiro-OMeTAD.　2D　materials,　which　can　be　stacked　via　van　der　Waals　(vdW)　forces　to　form　heterostructures,　open　up　new　possibilities　for　atomic-scale　engineering　of　perovskite　devices.　In　this　study,　the　electronic,　optical　properties　of　the　FAPbI3/SnS-vdW　heterostructure　are　investigated　using　first-principles　calculations.　The　SnS　monolayer　and　the　FAPbI3　surface　form　a　stable　Type-II　heterostructure　with　a　smaller　bandgap　compared　to　their　individual　components.　Through　selective　stacking　of　2D-SnS　at　PbI2　or　FAI　interfacial　atoms,　the　charge　transfer　direction　is　changed　accordingly.　The　favorable　interfacial　polarity,　smaller　distance,　and　stronger　bonding　of　SnS/PbI2　interface　result　in　a　better　HTL　properties.　Simulations　demonstrate　that　FAPbI3/SnS-based　PSCs　achieves　a　power　conversion　efficiency　(PCE)　of　21.30%,　comparable　to　the　traditional　FAPbI3/Spiro-OMeTAD　structure.　Moreover,　interfacial　effects　enhance　the　optical　absorption　of　the　FAPbI3/SnS　heterojunction,　thus,　the　SnS-based　PSC　exhibits　a　high　external　quantum　efficiency　(EQE)　with　an　extended　absorption　range.　This　work　provides　a　novel　perspective,　designing　principles　for　fabricating　low-cost,　high-performance　PSCs　based　on　vdW　heterostructures.　©　2025　Wiley-VCH　GmbH.