Unveiling the role of silver-promoted phase evolution in antimony sulfide thin films for photoelectrochemical activity

Antimony sulfide (Sb₂S₃) is a promising candidate for photoelectrochemical (PEC) water splitting due to its narrow band gap (∼1.7 eV), high optical absorption coefficient, and the earth-abundant nature of its constituent elements. However, deep-level defects promoting charge carrier recombination often hinder PEC performance. In this study, we investigated the effects of silver (Ag) incorporation on the structural, morphological, and photoelectrochemical properties of thermally evaporated Sb₂S₃ thin films. Compared with pristine films, Ag doping induces a shift in the preferred crystallographic orientation from (hk0) to (hk1), with notable morphological modifications and a reduction in surface roughness. Despite these structural improvements, the photocurrent density of the Ag-doped films decreased from 0.49 to 0.27 mA cm⁻² under standard illumination, indicating that Ag incorporation adversely affects charge transport and catalytic activity. These findings highlight the critical role of dopant-induced defects in governing the PEC performance of Sb₂S₃-based photoelectrodes.