Organic-inorganic　halide　perovskite　solar　cells　(PSCs)　have　experienced　remarkable　growth　over　the　past　decade,　largely　due　to　their　exceptional　power　conversion　efficiency　(PCE).　SnO2,　commonly　employed　as　the　electron　transport　layer　(ETL)　in　PSCs,　is　frequently　fabricated　using　the　chemical　bath　deposition　(CBD)　method.　In　traditional　CBD　formulations,　thioglycolic　acid　(TGA)　is　used　to　enhance　the　adhesion　of　SnO2　particles　to　the　substrate.　However,　the　presence　of　residual　TGA　on　the　ETL　surface　can　detrimentally　affect　device　performance.　To　mitigate　this　issue,　we　substituted　TGA　with　citric　acid,　which　is　free　of　thiol　groups,　preventing　defects　related　to　thiol-based　agents.　In　addition,　it　could　decompose　during　the　annealing　process　and　promotes　the　uniform　growth　of　SnO2　crystals　on　FTO　substrates.　Additionally,　KIO3　was　introduced　as　a　post-treatment　agent　to　oxidize　residual　Sn2+　to　Sn4+,　reducing　surface　oxygen　vacancies　and　increasing　lattice　oxygen　content.　This　synergistic　modification　enhances　SnO2　crystallinity　and　reduces　defects,　improving　charge　extraction　and　transport　within　the　device.　Furthermore,　improved　energy　level　alignment　between　SnO2　and　the　perovskite　layer　also　benefits　electron　collection　and　transport.　With　these　improvements,　the　optimized　devices　achieved　a　PCE　of　24.91　%　and　significantly　improved　operational　stability.　©　2025