Tailoring the optoelectronic behavior of hydrothermally deposited Sb2S3 thin films through controlled growth and thermal annealing

Abstract Antimony trisulfide (Sb 2 S 3 ) is a promising semiconductor for optoelectronic applications owing to its suitable direct band gap, high absorption coefficient, and compatibility with low-temperature solution processing. In this work, Sb 2 S 3 thin films were prepared by a hydrothermal method, and the effects of ethylenediaminetetraacetic acid disodium salt (EDTA-2Na)-assisted growth and post-annealing temperature on their structural, optical, surface, and optoelectrical properties were systematically studied. X-ray diffraction (XRD) results confirmed phase pure orthorhombic Sb 2 S 3 and showed that EDTA-2Na promotes stronger (020) preferential orientation and improved crystallinity. In addition, reduced residual strain/stress and dislocation density were observed in the EDTA-2Na-assisted films, indicating a more structurally relaxed crystal network. Scanning electron microscopy (SEM) analyses revealed denser and more homogeneous surface and cross-sectional morphologies in EDTA-2Na-assisted films. Ultraviolet–Visible (UV–Vis) transmission measurements indicated slight band gap narrowing after EDTA-2Na incorporation, while Energy-Dispersive X-ray Spectroscopy (EDS) analysis demonstrated improved compositional stability. Contact angle measurements further suggest enhanced surface uniformity and higher surface energy for EDTA-2Na-assisted samples. Among the investigated conditions, annealing at 300 °C under Ar provided the optimum balance between crystallization and defect control. The EDTA-2Na-assisted film annealed at 300 °C exhibited the strongest photoresponse characteristics, achieving a responsivity of 28.90 mA W −1 and a detectivity of 9.42 × 10 10 Jones under 365 nm illumination, together with stable and reproducible photoresponse in the UV–Vis region. The Sb 2 S 3 /EDTA-2Na-300 film also exhibited improved switching characteristics with reduced fall time, indicating suppressed carrier trapping and enhanced recombination dynamics. These results indicate that controlled growth chemistry and optimized thermal treatment are key parameters for improving the performance of hydrothermally deposited Sb 2 S 3 thin-film photodetectors.