[en] Sm³⁺-doped SrSnO₃ (SrSnO₃:Sm³⁺) nanopowders were synthesized by a simple hydrothermal method and followed by a heat treatment process. The as-synthesized nanopowders were assembled in dye-sensitized solar cells (DSSCs) to investigate their photoelectric properties. X-ray diffraction (XRD), scanning electron microscope (SEM), and energy-dispersive spectrometer (EDS) confirmed the formation of SrSnO₃:Sm³⁺ nanopowders with perovskite structure. The ultraviolet-visible absorption spectra and photoluminescence spectra indicate a down-conversion from ultraviolet light to visible light which matches the strong absorption region of the N719 dye. The DSSC based on SrSnO₃:Sm³⁺ photo-anode improved its photoelectric conversion efficiency (η) via the down-conversion of doped Sm³⁺. Under the irradiation of the simulated sunlight with 100 mW/cm², the DSSC based on SrSnO₃ doping with Sm³⁺ of 0.6 wt% showed the highest η of 1.54%, which improved 71.11% compared with the DSSC based on pure SrSnO₃. .