Antimony chalcogenides have become a family of promising photoelectric materials for high-efficiency solar cells. To date, single-junction solar cells based on individual antimony selenide or sulfide are dominant and show limited photoelectric conversion efficiency. Therefore, great gaps remain for the multiple junction solar cells. Herein, triple-junction antimony chalcogenides-based solar cells are designed and optimized with a theoretical efficiency of 32.98% through band engineering strategies with Sb₂S₃/Sb₂(S_0.7Se_0.3)₃/Sb₂Se₃ stacking. The optimum Se content of the mid-cell should be maintained low, i.e., 30% for achieving a low defect density in an absorber layer. Therefore, Sb₂(S_0.7Se_0.3)₃-based mid solar cells have contributed to elevate the external quantum efficiency in triple-junction devices by the full utilization of the solar spectrum. In a single-junction solar cell, the bandgap gradient is regulated through the Se content gradient along the depth profile of Sb₂(S_1−xSe_x)₃. Besides, an increasing Se content profile provides an additional built-in electric field for boosting hole charge carrier collection. Thus, the high charge carrier generation rate leads to a 17.96% improvement in the conversion efficiency compared with a conventional cell. This work may pave the way to boost the conversion efficiency of antimony chalcogenides-based solar cells to their theoretical limits.