Effect of sulfur doping on the photocatalytic performance of sputtered BiVO₄ thin films

Abstract BiVO 4 thin films doped with various concentrations of sulfur were fabricated using RF sputtering followed by post-deposition sulfurization. The incorporation of sulfur in the samples was calculated to be approximately 8–11 at% from the S2s peak in their X-ray photoelectron spectra. The optical bandgap of sulfur-doped BiVO 4 was generally smaller than that of the undoped sample. BiVO 4 films doped with ∼8 at% sulfur showed the highest photoelectrochemical performance compared to the undoped sample. Almost similar minority-carrier lifetimes in undoped and low sulfur-doped BiVO 4 , measured by time resolve photoluminescence, suggest that the crystal qualities in terms of the recombination properties are roughly the same for both cases. Thus, although further investigation may be necessary, the improved photocurrent in 8 at% sulfur-doped BiVO 4 in our study can roughly be attributed to the decrease in the bandgap, which facilitates more photoexcited carriers to contribute to the photoelectrochemical reaction. A further increase in sulfur doping above 10 at% distorted the BiVO 4 local crystal structure, inducing defects, thus resulting in a lower photocurrent.

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