A　large　number　of　defect　states　that　exist　at　the　interface　between　a　perovskite　film　and　an　electron　transport　layer　(ETL)　are　detrimental　to　the　efficiency　and　the　stability　of　perovskite　solar　cells　(PSCs).　It　is　still　a　challenge　to　simultaneously　passivate　the　defects　on　both　sides　by　a　stable　and　low-cost　ion　compound.　Herein,　we　demonstrate　a　simple　and　effective　versatile　strategy　by　introducing　hydrochloric　acid　into　SnO2　precursor　solution　to　passivate　the　defects　in　both　SnO2　and　perovskite　layers　and　simultaneously　reduce　the　interface　energy　barrier,　ultimately　achieving　a　high-performance　and　hysteresis-free　PSCs.　Hydrogen　ions　can　neutralize　-OH　groups　on　the　SnO2　surface,　whereas　the　Cl-　can　not　only　combine　with　Sn4+　in　ETL　but　also　suppress　the　Pb-I　antisite　defects　formed　at　the　buried　interface.　The　reduced　nonradiative　recombination　and　the　favorable　energy　level　alignment　result　in　a　significantly　increased　efficiency　from　20.71　to　22.06%　of　PSCs　due　to　the　enhancement　of　open-circuit　voltage.　In　addition,　the　stability　of　the　device　can　also　be　improved.　This　work　presents　a　facile　and　promising　approach　for　the　development　of　highly　efficient　PSCs.