Sb2Se3　solar　cells　have　achieved　a　power　conversion　efficiency　(PCE)　of　over　10%.　However,　the　serious　open-circuit　voltage　deficit　(VOC-deficit),　induced　by　the　hard-to-control　crystal　orientation　and　heterojunction　interface　reaction,　limits　the　PCE　of　vapor　transport　deposition　(VTD)　processed　Sb2Se3　solar　cells.　To　overcome　the　VOC-deficit　problem　of　VTD　processed　Sb2Se3　solar　cells,　herein,　an　in-situ　bandgap　regulation　strategy　is　innovatively　proposed　to　prepare　a　wide　band　gap　Sb2(S,Se)3　seed　layer　(WBSL)　at　CdS/Sb2Se3　heterojunction　interface　to　improve　the　PCE　of　Sb2Se3　solar　cells.　The　analysis　results　show　that　the　introduced　Sb2(S,Se)3　seed　layer　can　enhance　the　[001]　orientation　of　Sb2Se3　thin　films,　broaden　the　band　gap　of　heterojunction　interface,　and　realize　a　＇Spike-like＇　conduction　band　alignment　with　ΔEc　=　0.11　eV.　In　addition,　thanks　to　the　suppressed　CdS/Sb2Se3　interface　reaction　after　WBSL　application,　the　depletion　region　width　of　Sb2Se3　solar　cells　is　widened,　and　the　quality　of　CdS/Sb2Se3　interface　and　the　carrier　transporting　performance　of　Sb2Se3　solar　cells　are　significantly　improved　as　well.　Moreover,　the　harmful　Se　vacancy　defects　near　the　front　interface　of　Sb2Se3　solar　cells　can　be　greatly　diminished　by　WBSL.　Finally,　the　PCE　of　Sb2Se3　solar　cells　is　improved　from　7.0%　to　7.6%;　meanwhile　the　VOC　is　increased　to　466　mV　which　is　the　highest　value　for　the　VTD　derived　Sb2Se3　solar　cells.　This　work　will　provide　a　valuable　reference　for　the　interface　and　orientation　regulation　of　antimony-based　chalcogenide　solar　cells.　©　2024　Science　Press