A　suitable　substitution　of　the　lead　element　in　lead-based　halide　perovskites　is　a　feasible　approach　to　explore　lead-free　perovskite　material　with　excellent　stability,　tunable　band　gap,　high　optical　absorption,　and　better　photovoltaic　performance.　In　this　study,　the　toxic　lead　is　replaced　by　mixing　Ba/Si　and　Ba/Sn　to　develop　environmentally　friendly　perovskite　materials　with　excellent　properties.　MABa0.125Sn0.875I3　has　shown　evidently　improved　properties　in　terms　of　structural　stability　and　suitable　band　gap,　which　indicates　that　MABa0.125Sn0.875I3　can　become　the　most　potential　material　for　applications　in　single-junction　solar　cells.　Moreover,　MABa0.50Sn0.50I3　and　MABa0.25Sn0.75I3　can　be　promising　materials　for　the　top　cell　in　the　tandem　architecture　due　to　their　proper　band　gaps　(1.70–1.80　eV).　Moreover,　the　optical　absorption　coefficients　of　the　proposed　lead-free　perovskites　are　stronger　than　that　of　MAPbI3　in　the　range　of　500–800　nm.　Our　work　can　provide　new　insights　into　exploring　lead-free　perovskite　solar　cells　with　excellent　stability　and　suitable　band　gap.　©　2020　Elsevier　B.V.