Effects of excimer laser annealing energy on the properties of thermally evaporated tin antimony sulfide thin films and TEM characterization of the powder

Tin antimony sulfide (TAS) is one of the most promising compounds for the next generation of optoelectronic and thin film photovoltaic devices. TAS material was synthesized by a solid-state reaction using earth-abundant tin, antimony and sulfur elements. The structural properties of the TAS powder were investigated by transmission electron microscopy (TEM). X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and selected electron diffraction (SAED) were employed to establish the crystalline nature of the powder. The TEM observations demonstrated that the powder was polycrystalline in nature with rod-shaped structure. The effects of excimer laser annealing (ELA) at different pulse energies on the structural, morphological and optical properties of thermally evaporated TAS films were investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy measurements showed that the films annealed by an excimer laser of 248 nm were amorphous for weak energy densities whereas the sample irradiated with 111 mJ/cm− 2 was polycrystalline with a preferential \({\text{(}}\overline {{\text{2}}} {\text{1}}\overline {{\text{3}}} {\text{)}}\) orientation. The ELA effects on the optical properties were also studied in the wavelength range 300–1800 nm by using UV–Vis–NIR spectroscopy. The absorption coefficient of all samples in the fundamental absorption region is higher than 104 cm−1. We also found that the optical band gap decreases from 2.04 to 1.84 eV after irradiating the thin films under different laser energy densities.