Optimizing antimony trisulfide thin films: enhanced structural and optoelectronic properties via post-annealing in sulfur atmosphere

•High-quality thin films of antimony tri-sulfide were fabricated.•Ideal band gap of 1.5 eV was obtained for the optimized sample.•Enhanced physical properties were obtained for the optimized annealing temperature (300 °C).•Stoichiometric defects were mitigated in antimony tri-sulfide films at the optimum temperature. Antimony trisulfide (Sb2S3) is a promising material for photoabsorption due to its high absorption coefficient, low toxicity, and abundance in nature. However, various stoichiometric and crystalline defects have limited its practical applications. Herein, highly crystalline Sb2S3 thin films are fabricated via thermal evaporation and subsequent annealing in a sulfur atmosphere at different temperatures. The analyses of X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and optical properties reveal highly crystalline Sb2S3 thin films. The films showed reduced stoichiometric and crystal defects, while also displyaing enhanced optical and morphological properties. The improvement in the physical properties of the Sb2S3 thin films is attributed to the filling of sulfur deficiencies by extra sulfur vapors present during the thermal annealing process. Moreover, annealing the obtained Sb2S3 samples at different temperatures (ranging from 250 °C to 300 °C) reveals that the Sb2S3 films exhibit improved physical properties at 300 °C, which is considered to be the optimal annealing temperature. Our findings open up a pathway for the fabrication of highly crystalline Sb2S3 thin films, which could lead to the development of efficient optoelectronic devices.