Metal　halide　perovskite　solar　cells　have　experienced　unexpected　rapid　growth　in　the　past　decade　due　to　their　excellent　photoelectric　conversion　efficiency.　SnO2　has　attracted　great　attention　as　a　candidate　electron　transport　layer　to　replace　TiO2　in　perovskite　solar　cells.　However,　the　mixture　of　crystalline　and　amorphous　states　produces　a　large　number　of　oxygen　vacancy　defects　in　the　SnO2　lattice　and　surface,　leading　to　nonradiative　recombination　at　the　SnO2/perovskite　interface.　In　this　work,　an　effective　method　of　doping　the　rare　earth　element　Gd　in　SnO2　is　developed　for　planar　perovskite　solar　cells.　Doping　with　Gd　ions　can　effectively　passivate　oxygen　vacancy　defects　at　the　SnO2　interface,　leading　to　a　decrease　in　surface　energy,　which　contributes　to　facilitating　the　formation　of　high-quality　perovskite　films.　Gd　doping　can　also　optimize　the　energy　level　matching　between　SnO2　and　the　perovskite　layer,　thus　improving　the　charge　extraction　and　transport　capabilities.　As　a　result,　the　optimized　device　achieves　a　high　power　conversion　efficiency　of　22.40%,　with　a　certified　value　of　21.95%.　©　2022　Elsevier　B.V.