Enhanced photoelectrochemical performance of Zn-doped Bi₂S₃ thin films via seed-layer-assisted growth

Bismuth sulfide (Bi₂S₃) is a promising material for photoelectrochemical (PEC) water splitting, but its performance is limited by poor charge transport and high electron–hole recombination. This study enhances Bi₂S₃ performance by doping it with Zn using a seed-layer (SL) approach during chemical bath deposition. Three film types were prepared on FTO glass: pristine Bi₂S₃, SL-grown Bi₂S₃, and Zn-doped Bi₂S₃ (0.74–1.1 at%). The SL method improved the crystallinity and nanorod morphology, and reduced the bandgap from 1.4 to 1.32 eV. Zn doping induced a morphological shift to nanoparticles, increased the bandgap to 1.45 eV, and resulted in smaller crystallites. PEC analysis showed photocurrent densities of 4.5 mA cm⁻² (pristine), 10 mA cm⁻² (SL-grown), and 12.3 mA cm⁻² (Zn-doped) at 1 V vs. Ag/AgCl. The Zn-doped films exhibited improved stability and resistance to photocorrosion. The synergistic effects of SL growth and Zn doping significantly enhanced the structural, optical, and PEC performance of Bi₂S₃, making Zn-doped Bi₂S₃ a strong candidate for solar-driven water splitting.