Although a TiO2 overlayer is often used for protecting unstable light absorber materials in PEC water splitting, the Sb2Se3 is resistant to photocorrosion and we use it here to construct a p-n junction, which promotes photogenerated electron-hole pair separation. Subsequently, 2 nm Pt, acting as a hydrogen evolution catalyst, was deposited by sputtering. The device configuration of the Sb2Se3 photocathode is shown in Figure . The presence of TiO2 and Pt was confirmed by EDS measurement, as seen in Figure . The PEC performance of Sb2Se3 photocathodes prepared at different reaction durations (3-5 hours) was compared (Figure and Figure ). The Sb2Se3-Control photocathode exhibits a Jph of 14.4 mA cm -2 at 0 VRHE, which is higher than that of the Sb2Se3-3h and Sb2Se3-5h photocathodes. For Sn-doped Sb2Se3 films, the molar ratios of Sn 2+ /Sb 3+ prepared in the precursor solution were 0.5%, 1%, and 1.5%, respectively. Hereinafter, we refer to these films as Sb2Se3-Sn (0.5), Sb2Se3-Sn (1.0), and Sb2Se3-Sn (1.5). Figure displays the PEC performance of undoped and Sn-doped Sb2Se3 photocathodes evaluated in a 1 M H2SO4 (pH = 0) electrolyte by the linear sweep voltammetry (LSV) method under intermittent light illumination (AM 1.5 G, 100 mW cm ). An improvement in PEC performance in the Sb2Se3-Sn (0.5) photocathode, compared to the undoped Sb2Se3 photocathode, was observed. The champion device of the Sb2Se3-Sn (0.5) photocathode exhibits a Jph of 17.1 mA cm -2 at 0 VRHE, which is higher than that of the Sb2Se3-Control photocathode. Furthermore, the Sb2Se3-Sn (0.5) photocathode also achieved a superior fill factor (FF) of 28.7%, in contrast to the 21.5% FF obtained by the Sb2Se3-Control. However, further increasing Sn doping concentrations, Jph gradually decreased to 13.5 mA cm -2 and 12 mA cm -2 at 0 VRHE for the Sb2Se3-Sn (1.0) and Sb2Se3-Sn (1.5) photocathodes, respectively (Figure ).