Antimony　sulfide　(Sb2S3)　solar　cells　fabricated　via　hydrothermal　deposition　have　attracted　widespread　attention.　The　annealing　crystallization　process　plays　a　crucial　role　in　achieving　optimal　crystallinity　in　hydrothermal　Sb2S3　thin　films.　Nevertheless,　incomplete　crystallization　and　the　loss　of　sulfur　at　high-temperature　contribute　to　defect　recombination,　constraining　device　performance.　Herein,　a　two-step　rapid　thermal　processing　(RTP)　annealing　strategy　is　proposed　to　improve　the　crystal　quality　and　efficiency　of　Sb2S3　solar　cells.　The　annealing　process　in　Ar　protection　with　atmospheric　pressure　can　suppress　S　loss　caused　by　saturated　vapor　pressure.　The　two-step　RTP　annealing　with　the　330°C　low-temperature　and　370°C　high-temperature　process　ensures　high　crystallinity　and　vertical　orientations　of　Sb2S3　thin　films,　accompanied　by　a　reduction　in　defect　concentration　from　1.01　×　1012　to　5.97　×　1011　cm−3.　The　Sb2S3　solar　cell　achieves　an　efficiency　of　8.20%　with　an　enhanced　open　circuit　voltage　(VOC)　of　784　mV.　The　build-in　voltage　(Vbi)　of　1.17　V　and　irradiation-dependent　ideal　factor　(n)　of　1.48　demonstrate　enhanced　heterojunction　quality　and　suppressed　defect　recombination　in　the　devices.　The　presented　two-step　annealing　strategy　and　physical　mechanism　study　will　open　new　prospects　for　high-performance　Sb2S3　solar　cells.　©　Science　China　Press　2024.