Hydrothermally deposited Sb2S3 thin films: Effect of annealing conditions on the optoelectronic properties, the selenization, and photoelectrochemical performance

• An in-depth study of the post-deposition annealing under temperature and pressure conditions of the Sb 2 S 3 film. • Used a novel Raman analysis to estimate the inclination of the 1D/2D [Sb 4 S 6 ] n chains with respect to the substrate. • A prototype photoelectrochemical cell with an Sb 2 (S/Se) 3 active layer achieved 10.66 mA/cm 2 at 0 V vs. RHE. Sb 2 S 3 is a no-toxic and earth-abundant semiconductor with suitable bandgap (1.7–1.8 eV) for opto-electronic devices operating in the UV–Vis region. It has strong optical absorption, and being a low-dimensional material shows anisotropic properties. Its favorable optoelectronic characteristics and compatibility with low-cost and scalable fabrication methods make it a strong candidate for photovoltaic and other optoelectronic applications. In this work a detailed study of the opto-electronic properties of the material Sb 2 S 3 in relation to the post-deposition thermal processing of the thin films is discussed. The studies include the effect of annealing temperature, annealing duration, ambient pressure, and the partial substitution of sulfur (S) with selenium (Se). The studies were mainly focused on crystallite/grain orientation, Raman modes, and photocurrent response of the films subjected to the different annealing conditions. Raman analyses based on a reported empirical approach in literature showed that the quasi-1D [Sb 4 S 6 ] n chains are vertical, with an inclination of ≈ 16 degrees to the normal to the substrate, which remained within a 3 % change after the different annealing processes. The temperature and pressure variation studies found that the responsivity is maximum when [Sb 4 S 6 ] n chains are more closely aligned to the vertical, indicating a better charge transport. The role of S and Se vapor in the annealing chamber was manifested in the photoresponsivity. The films annealed in S atmosphere showed higher responsivity (5.29 × 10 4 A/W) compared to those annealed without S (1.79 × 10 4 A/W). The photoelectrochemical cell FTO/Au/Sb 2 (S 0.71 Se 0.29 ) 3 /CdS achieved 6.52 mA/cm 2 current at 0 vs E RHE which was further increased to 10.66 mA/cm 2 at 0 vs E RHE after surface modification with Pt, attaining a PEC efficiency of 1.5 % at 0.2 E RHE .